Beyond Imagination of Future Science

IEEE-NSS-MIC-RTSD Conference 2013 ************************************************ STATISTICS ************************************************ Nuclear Science Symposium (NSS) 807 papers Medical Imaging Conference (MIC) 592 papers Room-Temperature Semic. Detect. (RTSD) 137 papers Joint Sessions 40 papers Plenary Talks 7 papers TOTAL

1,583 papers

Papers submitted: about 2,800 Proceedings (suggested 8 page per paper): estimated more than 10,000 pages ****************************************** Welcome message from the 2013 IEEE-NSS-MIC-RTSD, General Chair, Prof. Hee-Joung Kim

Dear Colleagues and Friends, It will be our great pleasure to welcome you to Seoul and to the 2013 IEEE Nuclear Science Symposium and Medical Imaging Conference, and Room-Temperature Semiconductor X-Ray and Gamma-Ray Detectors workshop. The 2013 Conference will be held, for the 1st time in Asia-Pacific region, in the beautiful and historical city of Seoul, Korea, from October 27th November 2nd, 2013 at the spacious and modern COEX convention center. The conference center is located in the south part of the city, with easy access to the airport, and within walking distance of a variety of other hotels in many categories. It is conveniently linked to the city center, the historical museums and the ancient palaces by walk or by public transport. The hotels are a short walk from a collection of restaurants, shops, movie theaters, and other options in the Downtown city area. Our theme for 2013 is “Beyond Imagination of Future Science” [One author on page 227, paper R05-52, took the words of the Chairman seriously by demonstrating that his breakthrough inventions are “Beyond Imagination of Future Science” in discovering new particles and providing the highest potential to solve, through an effective early cancer detection, the world’s most deadly and costly calamity. The dialogue on this theme requested by the Chairman that will accelerate progress in promptly funding the most valuable inventions should be continued. This will save money and benefit all of us] and the Organizing Committee is planning a meeting of high scientific level that will include both oral and poster presentations and refresher courses on important topics. A commercial exhibition that will showcase state-of-the-art products and services from a wide range of companies will be held in parallel to the scientific sessions. The exhibit space will be specifically setup to allow both the 1

exhibitors and attendees amble space for discussions and exploration of common interests. In addition the presentation of original work, the conference also provides extensive educational opportunities via short courses and special emphasis seminars before and during the conference. The popular refresher courses will be held during the week to review current topics of special interest. As in past years, the conference will be making special efforts to obtain support grants for students to attend this important meeting and take full advantage of this unique scientific and educational opportunity. This meeting has always been a great opportunity to get together with old friends and to make new ones, to exchange ideas and share knowledge and experience in the nuclear science, medical imaging, and room-temperature semiconductor X-Ray and Gamma-Ray detector fields. This meeting expects to bring more peoples from Asia-Pacific areas to make 2013 conference very special and meaningful so that the IEEE NSS/MIC/RTSD get promoted greatly. The City of Seoul not only provides an excellent venue for our professional meeting, but also is an ideal location for attendees to bring their families. A variety of interesting tours will be offered so attendees and their companions can experience Seoul and the surrounding region to the full. City Tours are the most convenient and comfortable way to explore cities. The major sights and attractions of big cities are presented on a single tour. Nestled around the Han River is the Korean capital Seoul, a city of old and new. With thousands years of history, it has well preserved royal palaces, historical relics, and cultural treasures, yet state-of-the-art facilities and infrastructures as well. The Seoul City Tour bus runs a course that covers major points of interest in Seoul. Seoul has been the capital of Korea for about 600 years. Seoul has developed into a bustling metropolis, acting as the hub for political, economic, social, and cultural matters. The Han River runs through the heart of the city. The river divides the city in two; the northern part of the city is a focal point for culture and history, while the southern part is well known for its business district. In Seoul you can find ancient palaces and Royal Shrines of the Joseon Dynasty, as well as modern architectures and historical places such as Seoul World Cup Stadium, 63 CITY building, Insa-dong, Itaewon, Namdaemun and Dongdaemun Markets. On behalf of the organizing committee, I encourage you to make plans now to attend the 60th exciting NSS conference of the IEEE Nuclear and Plasma Sciences Society. I look forward to welcoming you to Seoul in October 2013 for the NSS-MIC-RTSD. Hee-Joung Kim 2013 NSS/MIC/RTSD General Chair ***************************** NP1(2) *********** NP1 NSS Plenary I Monday, Oct. 28 08:00-10:00 GBR 102-104 Session Chair: Gyuseong Cho, Korea Advanced Institute of Science and Technology, South Korea; Ikuo Kanno, Department of Nuclear Engineering, Kyoto University, Japan (08:00) Opening Address

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H. Kim General Chair, Yonsei University, Korea (08:10) Congratulatory Address M. Choi Ministry of Science, ICT & Future Planning, Korea (08:20) NP1-1, invited, From the Large Hadron Collider to the next Linear Collider L. R. Evans European Centre for Particle Physics (CERN), Geneva, Switzerland

The Large Hadron Collider at CERN, in operation since 2010 has already produced a wealth of experimental results, including the discovery of the Higgs boson at a mass of 125 GeV. Although the discovery potential of the LHC is large, there is broad consensus that a Linear Collider is needed to complement it. The unique strengths of a LC stem from the very clean experimental environment where centre-of-mass energy and initial polarization can both be controlled precisely. Two variants of a LC have been studied, the ILC, using technology that is mature where the energy can be increased in steps up to 1 TeV, and the Compact Linear Collider (CLIC) which has the potential to go about a factor of three higher in energy using technology that will still take a number of years to prove. The merits and limitations of these three machines will be discussed. (09:10) NP1-2, invited, Dark Matter and Neutrino Physics from Deep Underground Experiments Y. Kim Sejong University, Seoul, Korea

There are plenty evidence that the universe is dominated by dark components. Identifying the dark matter is one of the most challenging subjects in the modern science, and is critical to understanding the origin and the structure of the universe. We have better understanding about the neutrinos thanks to neutrino oscillation data obtained for last decades, but the yet unknown neutrino properties are needed to investigate the proposed leptogenesis of the universe. Many experiments are running or proposed at various deep underground laboratories and new detection techniques are emerging along with the development of nuclear science and technology. The state of the art underground experiments will be reviewed focusing on the status of low mass WIMPs issue, next generation neutrinoless double beta decay experiments, and the new, extreme detection techniques. ***************************** MP (2) ************** M01 MIC Opening and Plenary I Wednesday, Oct. 30 08:15-10:00 GBR 102-104 3

Session Chair: Jae Sung Lee, Seoul National University, South Korea (08:15) Introductory Remarks J. S. Lee Nuclear Medicine, Seoul National University, Seoul, Korea (08:30) M01-1, invited, See the Future of Medical Imaging through Consumer Electronics and Information Technologies J. Jo Samsung Electronics, Suwon, Korea

Medical Imaging System has been remarkably evolved for the last three decades. Particularly the imaging devices such as CT (computed tomography) and MRI (magnetic resonance imaging) are well deployed on a commercial scale with giving us much clearer view and more information. However the adoption of new technologies to the medical imaging devices has been quite sluggish compared to disruptive changes in IT industry, due to the patient safety and conservativeness against abrupt changes. On the other hand, huge waves of changes in CE (consumer electronics) and IT (information technologies) are underway and also influencing the medical equipment industry. For example, we used to find the flat-panel detector as a substitute for X-ray film from the only textbook. But it is now commercially available and widely deployed thanks to the amorphous-Si panel technology which had been commonly used in LCD (liquid crystal display). Accordingly the X-ray industry has been rapidly changing its paradigm from analog to digital. Hereafter, the new technology to bring a further change in the medical equipment industry and its value will be addressed. (09:15) M01-2, invited, Forays into Molecular Imaging M. G. Pomper Johns Hopkins Medical Institution, Baltimore, MD, USA

Although most clinical diagnostic imaging studies employ anatomic techniques such as computed tomography (CT) and magnetic resonance (MR) imaging, much of radiology research currently focuses on adapting these conventional methods to physiologic imaging as well as on introducing new techniques and agents for studying processes at the cellular and molecular levels in vivo, i.e. molecular imaging. Molecular imaging promises to provide new methods for the early detection of disease and support for personalized therapy. Although molecular imaging has been practiced for over 30 years in the context of nuclear medicine, other imaging modalities have also recently been applied to the noninvasive assessment of physiology and molecular events. Nevertheless, there has been sufficient experience with specifically targeted contrast agents and high-resolution techniques for MR imaging and other modalities that we must begin moving these new technologies from the laboratory to the clinic. This brief overview will outline molecular imaging from the development of targeted agents to clinical translation, with a focus on translational (small animal) and early clinical imaging. We will discuss the ability for molecular imaging to assess gene expression, and the various uses to which that can be put, and 4

provide examples of how existing or readily accessible molecular tracers and techniques can provide insight into rather complex biological phenomena in vivo. A variety of targets and disease processes will be discussed. **************************** NP2 (2) *************** NP2 NSS Plenary II Monday, Oct. 28 10:30-11:50 GBR 102-104 Session Chair: Ikuo Kanno, Department of Nuclear Engineering, Kyoto University, Japan; Gyuseong Cho, Korea Advanced Institute of Science and Technology, South Korea (10:30) NPSS Award Ceremony H. Kim 2013 General Chair, Yonsei University, Korea (11:10) NP2-1, invited, The 60th Meeting of the Nuclear Science Symposium W. Moses Lawrence Berkeley National Laboratory, Berkeley, USA

This presentation gives a brief history of the Nuclear Science Symposium, which is now meeting for the 60th time (and the first time in Asia). It starts with the “Rochester Conference on Scintillation Counters and Crystal Counters,” which was held in 1948 in Rochester, NY. It follows its sponsorship under the PGNS (Professional Group on Nuclear Science) portion of the IRE (Institute of Radio Engineers), up until 1963, when the IRE and AIEE merged to form the IEEE. It follows the creation of the Transactions on Nuclear Science in 1954 and the first time the conference was called the “Nuclear Science Symposium” in 1964. It also looks at how the scope and geographical coverage have changed over the years—spawning new conferences (such as the Particle Accelerator Conference), developing quasi-independent portions of the conference (such as the Medical Imaging Conference and the Symposium on Nuclear Power Systems), and partially absorbing previously independent conferences (such as the RoomTemperature Semiconductor Detector Workshop). (11:40) NP2-2, invited, Exploring Mars and Searching for Past Habitable Environments with the Curiosity Rover N. Bridges Applied Physics Laboratory, Laurel, MD, USA

The Mars Science Laboratory (MSL) Curiosity rover landed on Mars in August of 2012. Its main goal is to characterize past environments that may have been conducive to the evolution and sustainability of life. With a sophisticated set of 10 science instruments, it is a complex robotic field geologist and laboratory that will be exploring Mars at least through the summer of 2014 5

and probably longer. It is driving within Gale Crater, a location on Mars that once held liquid water and contains a large central mound with a stack of layers 3 times thicker than that in Earth’s Grand Canyon. Based on remote observations from Mars orbit, it has been determined that many of these layers are rich in clays and other minerals that formed or were deposited in the presence of water. The geographic goal of Curiosity is to drive up through the mound, named Mount Sharp, and examine each layer. As of the writing of this abstract (April 2013), the rover is not yet at this location, but rather on the crater floor. Nevertheless, evidence for past water has already been found, with conglomeritic rocks indicating a past flowing river, and mudstones formed in water under chemical conditions in which life could have existed. As a co-investigator on MSL since 2004, and involved with Mars missions for nearly 20 years, Dr. Bridges’ talk will focus on the development of the Curiosity rover, its results so far, and future plans. ********************** N1 (7) ************************************ N1 Astrophysics and Space Instrumentation I Monday, Oct. 28 14:00-16:00 GBR 101 Session Chair: Alex Nielsen, Institute for Gravitational Physics (AEI), Germany; Carsten Rott, Sungkyunkwan University, South Korea (14:00) N1-1, invited, KAGRA Large-Scale Cryogenic Gravitational Wave Telescope in Japan S. Miyoki Gravitational Wave Project Office, Institute for Cosmic Ray Research, The University of Tokyo, Kashiwa, Chiba, Japan On behalf of the KAGRA Collaboration

Large-scale cryogenic gravitational-wave telescope (named KAGRA) is currently under construction in the Kamioka mine in Japan. Direct detection of at least one gravitational wave (GW) event per year within 240 Mpc is expected. The direct detection of GWs is highly desired to obtain unique information about compact stars and supernovae and to be a new window to observe the Universe. Kilometer-scale GW detectors such as advanced LIGO in USA, advanced Virgo and GEO-HF in Europe are now being upgraded to obtain the same or higher sensitivity. KAGRA is regarded as one of an important base of the international gravitational wave detection network because KAGRA's position and the detector directionality can effectively cover dead angles of the other GW detectors and enhance the positioning accuracy of GW events. KAGRA has two unique features in its detector configuration. One is that it will be constructed underground, especially in hard rocks of Hida gneiss. Stable detector operation and few up-converted excess noise are expected due to low seismic motion not only in the observation band (10Hz ~ 1kHz) but also in the lower frequency range below the observation band. The other feature is to utilize cryogenic mirrors and suspensions for reduction of mirror and suspension thermal noises. For the technical demonstration of an underground and cryogenic laser interferometer for KAGRA, a Cryogenic Laser Interferometer Observatory (CLIO) with 100-meter baseline was newly built in 2004. We introduced sapphire mirrors cooled around 15 K, ultra-stable pulse-tube type refrigerators and a laser frequency (wave length) stabilization system for the precise length measurement to CLIO. Finally, the suspension thermal noise reduction according to its temperature and thermo-elastic 6

noise reduction of sapphire mirrors were demonstrated for the first time. Owing to these results, KAGRA project was approved in 2010. In this presentation, we will present the main part design of KAGRA. (14:30) N1-2, Progress and Future of Large Area Silicon Drift Detectors A. G. Vacchi experimental physics, INFN Italian Institute for Nuclear Physics, Trieste, Italy On behalf of the Redsox collaboration

E. Gatti and P. Rehak have proposed Silicon Drift Detectors (SDD) in 1983. It is now 30 years that this very versatile and elegant device evolves in different directions. The SDD operation principle has given rise to the development of a variety of solutions adapted to very challenging specific needs. All this was made possible by the rapidly evolving planar technology dedicated to the field of high performance detectors. The first large area SDD, for particles tracking in a high multiplicity environment, was published in 1990, while in 2007 more than 1 m2 of SDD was made operative in the internal tracking system of the LHC-ALICE experiment, demonstrating the possibility of industrial mass production with high production yield. Far from being exhausted, the large area SDD is continuing to develop, driven by very ambitious applications needing SDDs unique potentials. This presentation will give a short historical account and describe the path, which has lead to the present projects. (14:45) N1-3, Laser-Machined Tantalum Collimators for X-Ray Timing Missions M. Christophersen1, J. A. Christodoulides2, B. F. Phlips1, P. S. Ray3 1

Code 7654, U.S. Naval Research Laboratory, Washington, DC, USA Code 6363, U.S. Naval Research Laboratory, Washington, DC, USA 3 Code 7655, U.S. Naval Research Laboratory, Washington, DC, USA 2

We are developing tantalum X-ray collimators for LOFT (Large Observatory For X-ray Timing), a candidate mission selected by ESA. LOFT is devoted to X-ray timing and designed to investigate the space-time around collapsed objects. The collimator is micro-fabricated in a two-step process: (i) laser-machining of a hole array in Ta and (ii) chemical etching of the hole with the desired open fraction (hole vs. bulk volume). We fabricate and tested several prototypes. The angular response of the collimator was measured with a commercial X-ray diffractometer. Our currently most advanced prototype showed a FOV (field-of-view) of +/- 1 degree at 45 keV. Furthermore, we are developing mass-producing techniques for these collimators with an industrial partner (Fraunhofer USA). (15:00) N1-4, Development of SOI Pixel Sensors for X-Ray Astronomy T. Tanaka1, S. Nakashima1, H. Matsumura1, T. G. Tsuru1, A. Takeda2, Y. Arai2 1 2

Department of Physics, Kyoto University, Kyoto, Japan KEK, Tsukuba, Japan

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We have been developing monolithic active pixel sensors based on the Silicon-On-Insulator (SOI) technology for next generation X-ray astronomy satellites. Their good time resolution of ~ μs enables us to employ active shields, which drastically reduce non-X-ray backgrounds. Therefore, SOIPIX sensors with thick depletion layers are expected to have high sensitivity even above ~ 10 keV, where non-X-ray backgrounds are dominant, and offer wide band coverage of ~ 0.5-40 keV. In this talk, we will present the current status of our development. With our recent prototype sensor, XRPIX2, we achieved an energy resolution of 656 eV (FWHM) at 8 keV and readout noise of 64 e- (rms). We are now developing full-depleted back illumination sensors with high resistivity FZ wafers (ρ ~ 10 kΩ cm). Results of these latest developments are also reported in the talk. (15:15) N1-5, A Scientific Trigger Unit for Space-Based Real-Time Gamma Ray Burst Detection (I - Scientific Software Model and Simulations) S. Schanne1, H. Le Provost2, F. Chateau2, B. Cordier1, M. Cortial1, D. Gotz1, A. Gros1, P. Kestener3, P. Sizun2 1

DSM/IRFU/SAp, CEA Saclay, Gif sur Yvette, France DSM/IRFU/SEDI, CEA Saclay, Gif sur Yvette, France 3 DSM/MDLS, CEA Saclay, Gif sur Yvette, France 2

The on-board Scientific Trigger Unit (UTS) is designed to detect Gamma Ray Bursts (GRBs) in real-time, using the data produced by the ECLAIRs camera, foreseen to equip the future FrenchChinese satellite mission SVOM (Space-based Variable Objects Monitor). The UTS produces GRB alerts, sent to the ground for GRB follow-up observations, and requests the spacecraft slew to repoint its narrow field instruments onto the GRB afterglow. Because of the diversity of GRBs in duration and variability, two simultaneously running GRB trigger algorithms are implemented in the UTS, the so called Image Trigger performing systematic sky image reconstruction on time scales above 20 s, and the Count-Rate Trigger, selecting a time scale from 10 ms to 20 s showing an excess in count-rate over background estimate, prior to imaging the excess for localization on the sky. This paper describes both trigger algorithms and their implementation in a library, compiled for the Scientific Software Model (SSM) running on standard Linux machines, and which can also be cross-compiled for the Data Processing Model (DPM), in order to have the same algorithms running on both platforms. While the DPM permits to validate the hardware concept and benchmark the algorithms (see paper II), the SSM allows to optimize the algorithms and estimate the GRB trigger-rate of ECLAIRs/UTS. The result of running on the SSM a dynamic photon by photon simulation based on the BATSE GRB catalog is presented. (15:30) N1-6, Study of Event Reconstruction Algorithm for a Large-Scale Si/CdTe Multilayer Compton Camera Y. Ichinohe1,2, S. Takeda1, H. Odaka1, S. Watanabe1, T. Fukuyama1,2, M. Ohta1, T. Takahashi1,2, K. Nakazawa2, H. Tajima3, Y. Fukazawa4, T. Tanaka5 1

Institution of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Kanagawa, Japan 2 Department of Physics, Graduate School of Science, University of Tokyo, Bunkyo, Tokyo, Japan 3 Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya, Aichi, Japan 4 High Energy & Optical/Infrared Astrophysics Laboratory, Graduate School of Science, Hiroshima University, Higashi-Hiroshima, Hiroshima, Japan 5 Division of Physics and Astronomy, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto, Japan

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We present a novel event reconstruction algorithm for the Soft Gamma-ray Detector (SGD), which will be on board the ASTRO-H satellite. The main detector of the SGD is a large-scale Si/CdTe multilayer Compton camera; it consists of 112 thin solid-state pixel detectors of Si and CdTe, resulting in the total thickness of 19.2 mm for Si and 6 mm for CdTe and the efficiency reaches ~15% @ 100 keV and ~1% @ 662 keV with a very small geometrical volume of 10x10x10cm^3. Although the key for this detector to act as a Compton camera is an algorithm that can reconstruct the gamma-ray event correctly, such algorithms have not been well established so far mainly because the treatment of the fake signals, induced by secondary particles like fluorescence x-rays from CdTe, is difficult. We have developed a new event reconstruction algorithm that suits the SGD Compton camera. This algorithm is based on parameterizations that indirectly represent the probability of each sequence, and can be applied uniformly to any data that we can obtain using the SGD Compton camera, even if there are fake signals. To verify the validity of the algorithm, we have applied it to the experimental data of the engineering model of the SGD Compton camera. We have confirmed the validity of the algorithm by showing the following results; we have acquired the correct images of RI sources regardless of the source positions; the spectral continuum of RI sources, which can be regarded as the background, are properly subtracted based on the background rejection concept of the SGD. The detection efficiency increased by 25% @ 662 keV by using this algorithm. To inspect the algorithm more in detail, we conducted Monte Carlo simulations, and examined the correctness and fundamental limitation of the algorithm, and ensure that the algorithm is appropriate. We will present the details of the algorithm and results of the experiment and the simulation. (15:45) N1-7, In-Orbit Performance and Background of MAXI/GSC Gas Counters Operated on the International Space Station since 2009 M. Sugizaki MAXI Team, RIKEN, Wako, Saitama On behalf of the MAXI Team

MAXI (Monitor of All-sky X-ray Image) is the first astronomical mission performed on the International Space Station (ISS). It is working properly as the all-sky survey for more than three years since the mission instruments were activated on the ISS in 2009 August. The MAXI carries two kinds of X-ray slit cameras, Gas Slit Camera (GSC) and Solid-state Slit Camera (SSC), employing Xe-gas proportional counters and CCD imagers for X-ray detectors, respectively. In addition to these, Radiation Belt Monitors (RBMs) utilizing silicon PIN-diode detectors are equipped. The background of the GSC gas counters highly depends on the in-orbit particle radiation environment, which is largely parametrized by the geomagnetic field. Due to the large inclination angle (51 degree) of the ISS orbit, the ISS payloads pass through heavy particle-flux region at the high earth latitude every 90-minute orbital cycle. Since the degradation of carbonanode wires utilized in the GSC gas counters was found to be accelerated in a high backgroundrate condition, we restrict the counter operation in a low radiation region. We also reduce the anode voltage from 1650 V to 1550 V after the initial verification operation of about a month. In addition to these in-orbit radiation, the GSC background rates were found to vary by a factor of ~2, synchronized with the dock/undock of Soyuz spacecraft on the ISS. This is understood as due to a radioactive gamma-ray source on the Soyuz spacecraft, which is used in the elevation 9

monitor. In this paper, we report the results obtained from data in the first three years. ********************** N2 (8) ****************** N2 Gaseous Detectors I : Recent Developments Monday, Oct. 28 14:00-16:00 GBR 102 Session Chair: Leszek Ropelewski, CERN, Switzerland; Graham Smith, Brookhaven National Laboratory, United States

(14:00) N2-1, The GEM-based Inner Tracker of the KLOE-2 experiment G. Morello1, A. Balla1, G. Bencivenni1, P. Branchini2, A. Budano2, M. Capodiferro3,4, S. Cerioni1, P. Ciambrone1, E. Czerwinski5, G. De Robertis6, A. Di Cicco2, A. Di Domenico3,4, D. Domenici1, J. Dong1, G. Fanizzi6, G. Felici1, M. Gatta1, N. Lacalamita6, R. Liuzzi6, F. Loddo6, M. Mongelli6, A. Pelosi3,4, L. Quintieri1, A. Ranieri6, E. Tskhadadze1, V. Valentino6 1

INFN Laboratori Nazionali di Frascati, Frascati, Italy INFN Sezione di Roma Tre, Roma, Italy 3 INFN Sezione di Roma, Roma, Italy 4 Università Sapienza di Roma, Roma, Italy 5 Institute of Physics, Jagiellonian University, Krakow, Poland 6 INFN Sezione di Bari, Bari, Italy 2

For the next data taking period the KLOE apparatus is going to be integrated with new detectors. Among these, the Inner Tracker is inserted around the interaction region. It is composed by four cylindrical triple-GEMs with diameters from 260 to 440 mm and with a 700 mm active length. This detector is the first ever to use large area GEM realized with the single-mask technique by the CERN TE-MPE-EM group led by Rui de Oliveira. The GEM technology has been used in order to achieve the requirement to keep the material budget below 2% X0, allowing to limit the multiple scattering of low-momentum tracks. The peculiar readout pattern with XV strips provides a spatial resolution of 200 μm on the r-φ plane and 350 μm along the beam direction, equipped with a dedicated readout system developed within KLOE-2 collaboration consisting of a GASTONE ASIC connected to a General Interface Board with a configurable FPGA architecture and Gigabit Ethernet. The uniformity of the response for all the layers were checked by a 90Sr source and by cosmic rays runs. The results of the validation tests and the final assembly with the integration in the KLOE apparatus will be described as well as the beginning of the commissioning phase. (14:15) N2-2, Inner Chamber of Belle II CDC K. Chaiwongkhot1, U. Tippawan1, T. Kohriki2, N. Taniguchi2, S. Uno2, M. H. Nouxman3, K. A. Azmi3, S. Minemura4 1

Physics and Material, Chiang Mai University, Chiang Mai, Thailand Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization (KEK), Tsukuba, Japan 3 Physics, Malaya University, Kuala Lumpur, Malaysia 4 Physics, Nara Women's University, Nara, Japan 2

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The Belle II Central Drift Chamber (CDC) is a cylindrical chamber filled with the helium based gas mixture inside. It consists of 56 layers (14,336 sense wires and 42,240 field wires). The group of innermost eight layers of axial wires called small-cell chamber is constructed for reducing the occupancy in the face of the large beam background. The small-cell chamber, including its conical aluminum endplates and the carbon fiber reinforced plastic (CFRP) inner cylinder, with radius 160 mm, has the minimum azimuthal cell size of 7 mm and has its wires strung independently before installation in to the main chamber. The characteristic of the small-cell chamber, structure and wire configuration, for instance, are described. The results from the chamber test using the cosmic ray events are also presented. (14:30) N2-3, Design, Construction and Testing of the Straw Tracker for the NA62 Experiment H. Danielsson PH, CERN, Geneva, Switzerland On behalf of the NA62 Collaboration

The NA62 spectrometer should measure with good accuracy the direction and momentum of secondary charged particle originating from the decay region. In order to minimize multiple scattering, the spectrometer is operated in vacuum without physical separation from the upstream decay volume. The straw tracker has been chosen as the most promising detector to be operated in vacuum. It can be designed without frames and flanges close to the beam and so limits interactions from accompanying beam particles. The straws are made out of 36 mm thick polyethylene terephthalate film and are made through ultrasonic welding in the axial direction. They are coated with 50nm of copper and 20nm of gold on the inside of straw. The construction of the modules is in full swing and the detector will be installed in the fall of 2014 in order to be ready for the first physics run. We report on the design, construction and testing of the detector modules. Results from performance measurements in a cosmic ray set-up are also presented. (14:45) N2-4, Study of a Short Drift GEM Detector for Future Tracking Applications at RHIC B. Azmoun1, T. Cao2, M. Purschke1, C. Woody1 1 2

Physics Dept, Brookhaven National Laboratory, Upton, NY, USA Biomedical Engineering, Stony Brook University, Stony Brook, NY, USA

A short drift GEM tracking detector was studied in the H6 test beam at CERN as part of an effort to develop new tracking detectors for future experiments at RHIC. The detector consists of a triple GEM stack with a 16 mm drift gap and a COMPASS style readout plane with XY readout strips that is used in a mini TPC type configuration. Charge produced by tracks passing through the drift gap is collected over ~ 700 ns and sampled at rate of 25 ns which allows a measurement of the drift time of the charge clusters from the initial ionization. This enables a determination of the angle of the track passing through the detector as well as its position. The resulting vector can be used to improve the position resolution compared to simple charge centroid determination for tracks passing through the detector at large angles, and can also reduce the number of detectors required to measure tracks with a given precision. We have studied some basic characteristics of the short drift GEM detector in the lab using a beta source and cosmic rays, and have also studied 11

it more extensively in a test beam at CERN. This paper will report on the results of these studies. (15:00) N2-5, Development of Large Size Photon Detectors Based on THGEMs and Hybrid MPGD Architectures F. Tessarotto INFN - Trieste, TRIESTE, ITALY On behalf of the COMPASS THGEM Group

Relevant progress in the development of novel large-size gaseous detectors of single photons, mainly meant for Cherenkov imaging applications, has recently been achieved after an extensive R&D programme. In the first phase of the programme a complete characterization of the THGEM electron multipliers has been performed, together with extensive studies of the response of CsIcoated THGEMs in various configurations. Several small-size detectors based on THGEMs, arranged in a three layer architecture, have been built, tested in the laboratory and operated during test beam runs providing gain larger than 100.000 and time resolution better than 10 ns. Recent dedicated studies of the ion backflow to the photocathode have allowed to reduce it down to acceptable levels. A 300 mm x 300 mm active area photon detector has successfully been operated at the CERN PS T10 test beam. The challenges related to engineering aspects of large-size detector production are being actively faced: for example a good gain uniformity of THGEM response has recently been obtained by imposing stricter tolerance (3%) in the thickness uniformity of the THGEM dielectric. A new hybrid detector architecture has been introduced: a THGEM layer which acts as CsI support and pre-amplification device followed by a MICROMEGAS multiplication stage. Promising results have been obtained with this hybrid architecture. A set of 600 mm x 600 mm active area THGEM-based photon detectors will be provided for the upgrade of the RICH-1 Detector of the COMPASS Experiment at CERN. (15:15) N2-6, Development of a Hadron Blind Detector for the J-PARC E16 Experiment K. Kanno Department of Physics, Graduate school of Science, The University of Tokyo, Tokyo, Japan On behalf of the J-PARC E16 collaboration

A Hadron Blind Detector (HBD) has been developed for the J-PARC E16 experiment. The HBD is originally developed for the PHENIX experiment at RHIC. It is a mirror-less and window-less Cherenkov detector operated with pure CF4 and used for electron identification. It has a 500 mm radiator directly coupled to a readout element consisting of a triple GEM stack and pad readout at the bottom of the stack. The triple GEM stack has a ~300 nm thick CsI photocathode layer deposited on its upper surface. Cherenkov photons are converted into photoelectrons with the CsI photocathode. A mesh electrode above the triple GEM stack is used to control the field above the photocathode. By applying a proper bias voltage, ionization charge produced in the gap between the mesh and the top GEM is collected toward the mesh while photoelectrons are pulled into the holes of the GEM by the strong electric field near the holes. Using a such scheme, the HBD achieves a good hadron blindness. We have performed R&D of the HBD in the laboratory to have 12

good detector components, such as CsI photocathode, GEM foils, and high transmission gas radiator. Particularly we have studied GEM foils by changing the hole/pitch ratio of GEM since it affects both gain and collection efficiency of photoelectrons. Based on the results of these laboratory tests, we constructed a prototype HBD. The prototype HBD was tested at J-PARC K1.1BR beam-line with a 1 GeV/c beam of negative particles (mainly pions) containing a few tens of percent of electrons. We performed cluster size analysis to provide an additional pion rejection factor and the achieved rejection factor is more than 100. We present the performance of the HBD prototype and introduce some of our R&D efforts. (15:30) N2-7, The CALICE Digital Hadron Calorimeter: Calibration and Response to Pions and Positrons B. Bilki, K. Francis, J. Repond, J. Smith, L. Xia High Energy Physics, Argonne National Laboratory, Argonne, IL, USA

At a future lepton collider, such as the ILC or CLIC, the measurement of hadronic jets will play an important role in discovering or exploring physics beyond the current Standard Model of Particle Physics. Indeed, both the energy resolution and the mass resolution of multi-jet systems will be important in defining the physics reach of this new facility. Of particular interest will be the identification of electroweak bosons through their hadronic decay. Identification on an event-byevent basis will require an energy resolution of the order of 3-4% for a wide range of jet energies. A novel approach, named Particle Flow Algorithms (PFAs) is proposed to achieve this unprecedented jet energy resolution. PFAs attempt to measure each particle in a hadronic jet individually, using the component providing the best energy/momentum resolution. In this approach, charged particles are measured with a high-precision tracker, photons with the electromagnetic calorimeter and the remaining neutral hadronic particles in a jet with the combined electromagnetic and hadronic calorimeters. In this context the CALICE collaboration developed a Digital Hadron Calorimeter (DHCAL). A large-scale prototype DHCAL was built in 2008 2010 and was subsequently tested in the Fermilab test beam. The DHCAL uses Resistive Plate Chambers (RPCs) as active media and is read out with 1 x 1 cm2 pads and digital (1 - bit) resolution. With a world record of about 480k readout channels, the DHCAL offers the possibility to study hadronic interactions with unprecedented spatial resolution. Here we report on the results from the analysis of secondary beam events of momenta between 2 to 60 GeV/c collected in the Fermilab test beam. We present the details of the intricate calibration procedures and the utilization of detailed event topologies. (15:45) N2-8, The Analog Detector of the ARGO-YBJ Experiment S. Mastroianni INFN, Naples, Italy On behalf of the ARGO-YBJ Collaboration

The ARGO-YBJ experiment has been in stable data taking since November 2007 till February 2013 at the YangBaJing Cosmic Ray Laboratory (Tibet, P.R. China, 4300 m a.s.l.). Its main fields of research include gamma-ray astronomy with an energy threshold of a few hundreds GeV and 13

Cosmic Ray physics up to PeV energies. The ARGO-YBJ detector consists of a single layer of RPCs operated in streamer mode, housed in a large building of about 11,000 m^2. The signals from each RPC are picked up with 80 readout strips 61.8 cm wide and 6.75 cm long (23 strips/m^2) that allow the shower front reconstruction with an high space-time resolution. In order to fully investigate the PeV region, where the readout by strips saturates, an analog readout has been implemented by instrumenting each RPC with two large size electrodes of dimensions 1.23 1.39 m^2. Since December 2009 the RPC charge readout has been in operation on the entire central carpet (about 5800 m^2). The ARGO-YBJ detector equipped with the analog readout is able to measure the particle density at the core position where it ranges from tens to many thousands of particles per m^2. Here we describe in detail the analog readout of RPCs in ARGOYBJ, discuss the performance of the system that implements it and show the opportunities which open the experiment to Cosmic Ray physics above 100 TeV. ******************** N3 (7) ******************* N3 X-ray/Neutron Imaging Monday, Oct. 28 14:00-16:00 GBR 104 Session Chair: Yong Hyun Chung, Department of Radiological Science, Yonsei University, South Korea; Ronald Keyser, Software & Information Services, United States

(14:00) N3-1, invited, X-Ray Detectors for Security CT Imaging R. Deych, D. Schafer Analogic Corp., Peabody, MA, USA

Recent developments in dual energy volumetric computed tomography have demonstrated its advantages over other imaging modalities for luggage screening. USA Transportation Security Administration as well as European airport security agencies certified Volumetric CT scanners for explosive detection due to following advantages: high performance in automatic explosive detection, effectiveness for weapon detection, superior visualization capabilities. Performance and cost requirements for luggage screening differ from medical CT. As a result of these tradeoffs, various radiation imaging detectors have been used for luggage screening for explosive materials. In this paper we will review the current status of solid state integrating X-ray imaging detectors designed for high speed luggage scanning in the airports. Overview of the volumetric X-ray CT application in security imaging, and parametric requirements for scintillators, photo detectors, and data acquisition electronics will be presented. Methods of material identifications using dual energy CT, including x-ray source high voltage switching and dual energy detectors will be discussed. While energy integrating X-ray imaging detectors work in majority of the luggage security applications, new single photon counting detectors promise improved performance for material decomposition. (14:30) N3-2, Hybrid CMOS Sensor with Multi-Frame Storage for Ultra-Fast X-Ray Imaging 14

J. Porter, M. Sanchez, L. Claus, G. Robertson, R. Kay, J. Stahoviak, J. MacArthur, D. Trotter Sandia National Laboratories, Albuquerque, NM, USA

We have developed a camera that consists of a silicon photo-detector array directly connected to a CMOS readout integrated circuit (ROIC) that can capture multiple x-ray images with integration times as short as 1 nanosecond and interframe times as short as 2 nanoseconds. This camera was designed to record transient x-ray images of high-energy-density science experiments on the Z Machine at Sandia National Laboratories. In these experiments, typically lasting for only a few billionths of a second, a 26-millon-ampere 80-trillion-watt electrical pulse is used to quickly heat and compress materials to high temperatures and pressures. Both the silicon photo-detector array and the CMOS ROIC are fabricated at Sandia's Mesa Fabrication facility. The 1024x448 pixel photo-detector array has a 25 micron pitch with nearly 100% fill factor, is sensitive to x-rays up to approximately 10 keV in energy with high efficiency, and has subnanosecond temporal response. The corresponding 1024x448 pixel ROIC has 2-frame in-pixel analog storage of a maximum of nearly 3 million electrons per pixel for each frame. We are designing next-generation cameras having 4-frames per pixel, more flexible high-speed timing to enable interlaced image capture, and that can be configured with detector arrays with optimized sensitivity to visible light down to 350 nm, soft x-rays down to 100 eV in energy, or electrons with energies down to 1 keV. (14:45) N3-3, Modular Pixelated X-Ray and Neutron Detector System with the Spectroscopic Capability and Fast Parallel Read Out D. Vavrik1, J. Jakubek2, M. Holik2, V. Kraus2, P. Soukup2, D. Turecek2 1 2

Institute of Theoretical and Applied Mechanics, Prague, Czech Republic Institute of Experimental and Applied Physics, Prague, Czech Republic

Modular pixelated detector system was developed for imaging applications, where spectroscopic analysis of traces of detected particles is advantageous. The energy profile and shape of each recorded particle track can be utilized e.g. for high resolution energy sensitive X ray radiography, high resolution neutron imaging or imaging in hadron therapy. The track shape analysis allows very high selectivity and background suppression. The presented modular system allows assembling of various 2D and 3D detector configurations where each detector is read-out separately. Each module consists of single Timepix device with edgeless silicon sensor connected to independent parallel readout interface FitPix 3.0. The edgeless sensor technology makes possible tight side by side placement of detector modules enlarging their sensitive area. The mechanical adjustable holder with fine positioning is designed for precise 3D stacking of modules which improves detection efficiency. Thus it is easily possible to arrange e.g. 3 layers with four detectors in each layer. The newly developed USB 2.0 based FITpix 3.0 interface consists of baseboard and exchangeable adapter board supporting all devices of medipix family (Timepix serial or parallel, Medipix3 RX). It offers high read out speed of up to 850 frames per second, with on-line lossless data compression. The high performance of the system allows obtaining fully spectroscopic X-ray images in 2 minutes. The performance in few applications of the modular system with different detector configurations will be presented. (15:00) N3-4, Bubble Masks for Time-Encoded Imaging of Fast Neutrons E. Brubaker, J. Brennan, A. Nowack, M. Sweany, D. Throckmorton

15

Sandia National Laboratories, CA, Livermore, CA, USA

Time-encoded imaging is an approach to directional radiation detection that is being developed at SNL with a focus on fast neutron directional detection. In this technique, a time modulation of a detected neutron signal is induced typically, a moving mask that attenuates neutrons with a time structure that depends on the source position. An important challenge in time-encoded imaging is to develop high-resolution two-dimensional imaging capabilities; building a mechanically moving high-resolution mask presents challenges both theoretical and technical. We have investigated an alternative to mechanical masks that replaces the solid mask with a liquid such as mineral oil. Instead of fixed blocks of solid material that move in pre-defined patterns, the oil is contained in tubing structures, and carefully introduced air gapsbubblespropagate through the tubing, generating moving patterns of oil mask elements and air apertures. Compared to current movingmask techniques, the bubble mask is simple, since mechanical motion is replaced by gravitydriven bubble propagation; it is flexible, since arbitrary bubble patterns can be generated by a software-controlled valve actuator; and it is potentially high performance, since the tubing and bubble size can be tuned for high-resolution imaging requirements. We have built and tested various single-tube mask elements, and will present results on bubble introduction and propagation as a function of tubing size and cross-sectional shape; real-time bubble position tracking; neutron source imaging tests; and reconstruction techniques demonstrated on simple test data as well as a simulated full detector system. (15:15) N3-5, On the Resolving and Source Identification Limitations of a Real-Time FastNeutron Imaging System J. Beaumont1, M. Mellor2, M. J. Joyce1 1 2

Department of Engineering, Lancaster University, UK, Lancaster, Lancashire, UK Createc Ltd, Cockermouth, Cumbria, UK

The imaging of fast neutrons from spontaneous fission and spallation sources has great potential in aiding the assessment of radiation environments. Knowledge of the spatial dependence of neutron flux allows the location of neutron sources to be deduced, additionally contributing the neutron components of radiation dosimetry calculations which can strongly impact strategies in scenarios such as decommissioning or accident response. Using a prototype mixed-field imaging system at Lancaster University we have previously reported to the Nuclear Science Symposium in 2012 that neutron spectroscopy can be used alongside imaging techniques to identify different types of neutron sources. This research seeks to further investigate these applications by experimentally determining the resolving power of the system, in both imaging and source-recognition techniques. The use of the organic liquid scintillator EJ-301 coupled with new developments in fast digitising electronics have complimented pulse-shape discrimination techniques by allowing discrete detection of neutron and gamma-rays in real-time. Collimation and remote motor control allows human-inaccessible radiation environments to be scanned, sampling neutron and gammaray flux vectors. The goal being to assess an area spatially, locating gamma-ray and neutron emitters and to recognise the isotopes and spallation sources present. The additional insight of the neutron field allows radiation hazards to be identified even in situations where fertile materials have low gamma-ray contributions, are shielded by high-Z materials or where the gamma-ray background is high in comparison. This paper seeks to further investigate the limitations of the system as it stands, and to find further improvements in the system design for mixed-field imaging 16

and analysis. (15:30) N3-6, An Air Fluorescence Imaging System for the Near-Field Detection of Alpha Contamination E. L. Inrig1, F. Evans1, A. Jones1, I. Watson1, V. Koslowsky2 1 2

Radiological Analysis & Defence, Defence R&D Canada - Ottawa, Ottawa, Ontario, Canada Bubble Technology Industries, Chalk River, Ontario, Canada

Detection and measurement of alpha contamination in the field presents a significant challenge. Since alpha particles travel only a few centimetres in air, conventional detection techniques require measurements to be made at extremely close range. As was observed in the course of the investigation that followed the 210Po poisoning of Russian national Alexander Litvinenko in 2006, widespread monitoring for alpha contamination can cost a great deal of time, money, and manpower. The Multi-spectral Imaging System for the Detection of Radiological Contamination employs a novel approach for the detection of short-range radiation: rather than detecting the radiation directly, it measures radiation-induced fluorescence in the air surrounding a radioactive source. An optical system incorporating position-sensitive photomultiplier tubes is used to image the air-fluorescence signal over a user-defined area, identifying regions of possible contamination in a fraction of the time required using conventional detectors. Detailed results from testing of the completed fluorescence imager prototype was carried out at Defence Research & Development Canada Ottawa using 241Am point and area sources as well as area sources prepared using shortlived 225Ac (t1/2 = 10.0 d) will be presented. Preliminary analysis of the results indicates that distributed 225Ac activity as low as 1 kBq/cm2 (total activity under 100 kBq) can reliably be detected at a standoff distance of 1.5 m in less than 10 seconds. The influence of factors such as ambient lighting conditions and source-detector distance on the detector sensitivity will be discussed, along with signal processing techniques. With further development, this technology could provide a valuable tool for in-situ alpha contamination measurements, with potential applications for law enforcement, public security, and the nuclear industry. (15:45) N3-7, Development and First Results of the Yale PIXeY Two-Phase Xenon Detector N. Destefano1, M. Gai1, D. McKinsey2, E. Bernard2, B. Edwards2, N. Larsen2, M. Horn2, B. Tennyson2, A. Hackenburg2 1 2

University of Connecticut, Storrs, CT, USA Yale University, New Haven, CT, USA

PIXeY (Particle Identification in Xenon at Yale) is a two-phase (liquid/gas) xenon prototype detector with 3-kg active mass. The two-phase xenon technology has many applications that include gamma-ray imaging, neutrinoless double beta decay searches, and dark matter searches. PIXeY was built to optimize energy resolution and gamma/neutron discrimination, with a number of technological improvements over previous work. Parallel-wire grids, which control the drift and proportional-scintillation fields, are optimized both for light collection efficiency and field uniformity. High quantum efficiency Hamamatsu R8778 PMTs, high-reflectivity Teflon walls, and charge-light anti-correlation techniques are also incorporated. PIXeY will serve as a platform for future improvements, including multiple optical volumes and single wire readout for R&D on gamma-ray imaging and track-imaging studies. The latest progress on the detector will be 17

presented. ****************** N4 (8) *********************** N4 Scintillator Properties Monday, Oct. 28 14:00-16:00 GBR 105 Session Chair: William Moses, Lawrence Berkeley National Laboratory, United States; Marek Moszynski, National Centre for Nuclear Reserarch, Poland (14:00) N4-1, New Scintillator Materials for Nuclear Physics Applications: an In-Beam Test at ALTO G. Hull1, J. Bettane1, N. J. Cherepy2, B. Genolini1, M. Josselin1, I. Matea1 1 2

Institut de Physique Nucleaire d'Orsay, Orsay, France Lawrence Livermore National Laboratory, Livermore, CA, USA

A number of new instruments for particle and gamma detection have been built or are under development as part of the equipment of the new radioactive ion facilities that are under construction in Europe, as PARIS for SPIRAL2 at GANIL or CALIFA for FAIR at GSI. In this framework we are interested in studying new developed scintillators with advanced detection properties for application in nuclear physics. As a matter of fact in these latest years there is a renewed interest, in the chemistry and material science community, to search for new luminescent materials as real alternatives to LaBr3:Ce. Some new proposed scintillators, deserving close attention due to their promising detection features, have already been grown in cm3 scale samples, and thus in volumes suitable for our interest. In this communication we will report on the outcomes of the test in-beam at the ALTO (Accelerateur Lineaire et Tandem Orsay) facility of several new scintillators, with both crystalline and transparent ceramic structure. In particular we studied the response of CeBr3, SrI2:Eu, CLYC and GYGAG:Ce, under high energy gamma irradiation produced in the nuclear reaction between the proton beam and light nuclei targets. Reactions induced by energetic protons on light targets lead to the emission of high-energy photons. In an in-beam campaign we can thus measure the scintillators energy resolution, light production and detection efficiency over a wide range of monochromatic gamma energies, up to 20 MeV, otherwise not available with standard radioactive sources. (14:15) N4-2, Temperature Dependence on Scintillation Properties of Gd2Si2O7:Ce Scintillators Grown by a TSSG Method for Gamma-Rays Y. Tsubota1, J. H. Kaneko1, M. Higuchi1, S. Nishiyama1, H. Ishibashi2 1 2

Graduate school of Engineering, Hokkaido University, Sapporo, Hokkaido, Japan Hitachi chemical co. ltd, Hitachinaka-shi, Ibaraki, Japan

Single crystal Gd2Si2O7:Ce (GPS:Ce) scintillators were grown by a top seeded solution growth (TSSG) method and their scintillation properties in high temperature (RT to 573 K) were measured. Single crystal GPS with several cerium concentrations, (Gd1-xCex)2Si2O7 (x=0.01, 18

0.025, 0.10), were synthesized with a RF-type Czochralski furnace. Obtained crystals were annealed in N2 for 12 hr., cut into c.a. 5 x 5 x 5 mm and all faces were polished. GPS scintillators were settled into the vacuum chamber and pulse height spectra for 662 keV gamma-rays from 137 Cs were measured. GPS scintillators were heated by an ohmic heater through the Cu and Al thermal guide. The scintillation lights was collected by the quartz light guide through the gap of several mm. The light guide was optically connected to the photo multiplier tube at the outside of the chamber. Output signals from the last dynode of the PMT was amplified by a delay-line amplifier, (460, Ortec 460) pulse width were stretched by a stretcher (542, Ortec). The shaped signals were measured by the multi-channel analyzer (Yokogawa, WE7562). Pulse height spectra from RT to 523K for Ce concentration of 1, 10% and to 573K for Ce concentration of 2.5% was measured. For the triclinic GPS with 10% of Ce concentration, light yield was increased up to 136% of the RT, then decreased to 65% at 523K. On the other hand, the orthorhombic GPS with 1 and 2.5% of Ce concentration did not decreased at 523K. For the GPS with 2.5% of Ce concentration, it kept light yield of 74% at 573K compared to that of RT. (14:30) N4-3, Scintillation Properties of CeBr3 with Divalent Doping U. Shirwadkar1, R. Hawrami1, E. Van Loef1, J. Tower1, M. Squillante1, K. Shah1, P. Guss2, T. Stampahar2, M. Foster3, B. Wong3, F. P. Doty3, D. Yuan4 1

Radiation Monitoring Devices, Watertown MA, USA Remote Sensing LaboratoryNellis, Las Vegas, NV, USA 3 Materials Chemistry Department, Sandia National Laboratories, Livermore, CA, USA 4 National Security Technologies, Los Alamos, NM, USA 2

In this paper we present scintillation properties of CeBr3 crystals grown with divalent dopants. Small diameter (up to ~ 1cm) single crystals of CeBr3 doped with Ca2+, Mg2+, Cd2+, and Sr2+ have been grown at RMD. We have observed Ca2+ to be the most promising dopant, since it significantly improves the non-proportionality and energy resolution of pure CeBr 3. The nonproportionality was measured in the energy range from 32 keV up to 1274 keV. It has been observed that at 32 keV CeBr3:Ca2+ deviates about 4 % from the ideal case (10 % for pure CeBr3). We achieved an excellent energy resolution of 3.2 % at 662 keV and light output of ~ 62,000 photons/MeV. These results and other trends in the radioluminescence and decay times of doped CeBr3 crystals will be discussed. (14:45) N4-4, Luminescence Properties of Scintillation Crystals Based on Mixed Rare-Earth Fluorides J. Pejchal1,2, K. Fukuda3, S. Kurosawa1,4, Y. Yokota1, A. Yoshikawa1,4 1

Institute for Materials Research, Tohoku University, Sendai, Japan Dept. of Optical Materials, Institute of Physics AS CR, Prague, Czech Republic 3 Tokuyama corp, Tokyo, Japan 4 New Industry Creation Hatchery Center, Tohoku University, Sendai, Japan 2

The development of new radiation detection systems based on the vacuum ultraviolet (VUV) scintillators has been started recently. These scintillators can be coupled with advanced VUV photodetectors such as position-sensitive gas electron multipliers (GEM), micro-pixel chambers [1] or VUV-sensitive photomultipliers with CsI-coated photocathodes [2]. ErF3 has been recently 19

considered as one of the candidates for VUV scintillators. It has been studied recently from the point of view of the scintillation applications for the first time by some of us [3]. The phase transition from hexagonal to tetragonal modification occurs some 20C below the melting point, which is at 1140C. Resulting difficulties of crystal growth have been overcome with modified micro-pulling-down method and it was proved that high-quality crystals can be prepared. In some cases, Nd3+ ion has been introduced as a luminescence center. In some hosts, the Er3+ 5d-4f emission spectrum coincides with the Nd 4f-5d absorption band and thus the energy could migrate over the Er3+ 5d levels to the Nd3+ ones [4]. Similar mechanism was expected in the ErF3:Nd. This concept is similar to that reported for PrF3:Ce scintillator, where an efficient energy transfer from the Pr3+ 1S0 4f-level to the 5d-levels of Ce3+[4]. However, it was proved that the energy transfer mechanism practically does not work and only negligible Nd3+ luminescence was observed. It is, as can be expected, caused by strong energy migration over the Er3+ levels in such a concentrated system. Therefore, we decided to dilute the ErF3 by LuF3 to hamper such energy migration and optimize the scintillation performance. The luminescence and scintillation properties of ErF3:Lu,Nd single crystals will be presented and discussed. (15:00) N4-5, Scintillation Properties and Temperature Response of Sr and Ba Co-Doped LaBr3:Ce K. Yang1, P. R. Menge1, J. J. Buzniak1, V. Ouspenski2 1 2

Saint-Gobain Crystals, Hiram, OH, USA Saint-Gobain Recherche, Aubervilliers, France

Saint-Gobain Crystals has been investigating the optimization of the scintillation properties of LaBr3:Ce by introducing a small amount of co-dopants. As we previously reported, scintillation light yield and energy resolution of LaBr3:Ce can be significantly improved by co-doping with alkaline earth metals. This performance improvement is retained in crystals as large as ϕ60mm x80mm. In this report, up-to-date results on Sr co-doped and Ba co-doped LaBr3:Ce are presented. A close-coupled Compton coincidence system has been constructed to continuously characterize the scintillation light yield non-proportionality of standard and co-doped LaBr3:Ce crystals from ~10 keV to ~900 keV. Scintillation light yields and time profiles from -40 C to 175 C are also reported. (15:15) N4-6, Study on Scintillation Properties for Pyrochlore Crystal S. Kurosawa1, Y. Shoji1, T. Shishido1, A. Suzuki1, Y. Yokota2, K. Kamada2, A. Yoshikawa1,2,3 1

IMR, Tohoku University, Sendai, Japan NICHe, Tohoku University, Sendai, Japan 3 C&A, Sendai, Japan 2

Recently, the pyrochlore crystal structure described as A2B2O7, have been studied as scintillation materials. However, most components are not congruent (e.g. Gd2O3 SiO2 system), and melt growth is difficult. In order to obtain the congruent components, we doped approximately 10-50% La into the host material. Then we succeeded in obtaining a Ce:(La, Gd)2Si2O7 (Ce:La-GPS) scintillator with a good energy resolution (FWHM) of 5% at 662 keV , while the crystal size was small (~10 mm3). In addition, other pyrochlore crystals are expected to be candidates of novel scintillation materials with a better light output or energy resolution. Moreover, some scintillation 20

properties are expected to remain very high even when the temperature increases up to 450 K, because Ce:LPS and Ce:GPS were reported this characteristic. Although Ce:LPS cannot be applied to oil well logging due to the intrinsic background, Ce:GPS and other material can be. In this paper, (i) we search novel materials with a Pyrochlore structure, 1 mol% Ce-doped (Lax, Luy, Gd1-x-y)2(Gez, Si1-z)2O7 (0≤x 500g). Further discussion is finally given on consequent possible new applications in gamma-ray spectroscopy. NPO2-96, Development of a New Gas Injection System for the Linac4 Accelerator at CERN R. Guida1, P. Carri1, S. Izquierdo Rosas2, J. Lettry3, J. Rochez2, A. Wasem1 1

PH-DT, CERN, Geneva, Switzerland EN-ICE, CERN, Geneva, Switzerland 3 BE-ABP, CERN, Geneva, Switzerland 2

The linear accelerator is the first vital stage of any hadron accelerator complex. The reliability of the linac injector has to be the highest of the entire accelerator complex: in fact, a fault of the linac shuts down all other machines. The currently used Linac2 is in operation since 1978 and even if it has reached an excellent reliability, significant issues related to ageing of components are now appearing. The Linac4 is an H- linear accelerator, intended to replace Linac2 as injector to the PS Booster (PSB). It is a machine 90 m long, that will accelerate H- ions up to 160 MeV. This contribution describes the layout and control system for the hydrogen (H2) gas injection module for the Linac4: Ion source and Low-Energy Beam Transport (LEBT). The gas injection system is providing a stable and constant hydrogen pressure in the range between 400 and 2800 mbar for reliable ion source operation. A Bronkhorst pressure regulator is used to control the H2 supply pressure to ion source and LEBT. In both systems, a second regulator is already installed and immediately available in order ensure the maximum reliability of each system. The achieved pressure stability is better than 0.5 mbar. Moreover, the supply pressure is adjusted according to the environmental temperature in order to maintain a stable gas density. The total hydrogen consumption is monitored by means of thermic mass-flow meters (MFMs) and recording the pressure drop in the supply cylinders. In case an abnormal consumption is detected, the gas system control immediately closes the hydrogen supply and put the whole module in a safe condition. The Ion source and LEBT modules are controlled by means of a software running on an industrial PLC. A pvss interface is used to monitor and control the process. The two gas injection systems are already in operation at the Linac4 test setup and they are stably performing the end of 2012. The performances achieved will be discussed in the present contribution. NPO2-97, Developments Towards a U.S. Short Baseline Reactor Antineutrino Oscillation Experiment N. Bowden Lawrence Livermore National Laboratory, Livermore, CA, USA On behalf of the U.S. Short Baseline Reactor Experiment Interest Group

While much progress has been made in understanding the neutrino sector in recent decades, persistent hints at the existence of additional sterile neutrino flavors remain an unanswered puzzle. These include unexplained event excesses in the LSND and MiniBOONE experiments, suggestions from astrophysical measurements, and the Reactor Antineutrino Anomaly. There is a strong desire in the neutrino physics community for new experimental inputs that can provide 411

definitive confirmation or exclusion of these suggestive indications via the measurement of oscillation patterns. Here we describe efforts towards a Short Baseline Reactor experiment using one of several unique U.S. research reactor facilities. Through careful siting and design, such an experiment would be sensitive to sterile neutrino driven oscillations in both baseline length and antineutrino energy. We will describe the experimental concept, the challenges that must addressed, and the overlap with efforts to develop compact antineutrino detectors for reactor monitoring and safeguards. NPO2-98, Integrated High Voltage Photo-Voltaic Device for Radiation Detector Systems J. Segal1, C. Kenney1, M. Breidenbach1, G. Gratta2, A. Tomada1, C.-E. Chang3 1

SLAC National Accelerator Laboratory, Menlo Park, CA, USA Department of Physics, Stanford, Stanford, CA, USA 3 Department of Electrical Engineering, Stanford, Stanford, CA, USA 2

Many detectors used in particle physics and photon science require a high bias voltage to function properly. The needed electrical potentials range from tens of volts to hundreds of kilovolts. In most instances the applied voltage must be gradually raised or tuned depending to the conditions, which necessitates the ability to precisely vary the bias. Traditional electrical supplies are often expensive, bulky, difficult to design, subject to grounding issues, and prone to failure. There are safety concerns associated with such high potentials, and restricting the location of these voltages only to where they are utilized reduces this hazard. To address these and other issues a novel process has been developed to provide micro-machined, integrated photovoltaic diodes that are scalable up to at least 10 kV per chip and under suitable illumination supply currents of over a mA. The device is built on a silicon-on-insulated substrate and uses plasma-etched trenches to isolate each diode from its neighbors. Prototype devices have been manufactured and test results will be reported on. NPO2-99, Integrated, Self-Sealing, Micro-Fabricated Coolant Channels A. Tomada1, P. Grenier1, M. Oriunno1, S. Dong1, C. Kenney1, J. Hasi1, J. Van Heijningen2 1 2

PPA, SLAC, Menlo Park, CA, USA NIKHEF, Amsterdam, Netherlands

Integrated, Self-sealing, Micro-fabricated Coolant Channels A.Tomada, P. Grenier, S. Dong, M. Oriunno, C. Kenney, J. Hasi, J. Van Heijningen SLAC National Accelerator Laboratory, USA Nikhef Nationaal Instituut Voor Subatomaire Fysica, Netherlands Abstract Among the most critical challenges of a vertex detector in high-energy-physics, collider-based experiments are the amount of mass in the structure and the increasing heat density of the readout electronics, which may affect the stable operations of the detector in highly irradiated environment inducing thermal runaway. As particles traverse a material they undergo multiple scattering, which causes information about their original trajectory to be degraded. Vertex detectors generally have sensor and or circuit chips distributed across their sensitive area in several layers. To maintain the desired performances, the thermal gradients between the sensor and the cooling medium must be kept low to improve the safety margin on the thermal runaway, to reduce the thermo-mechanical stress due to the mismatch of the coefficients of thermal expansion but also optimize the design point of the cooling system. Typically metal pipes are used to transport refrigerant with an increased mass of 412

the system and negatively impacts the science reach. Fabricating micro-channels within the nondevice side of a circuit chip, would allow a dramatic increase of the heat exchange area close to the heat-generating components in conjugation with much higher heat transfer coefficients. This concept provides an integrated design, which optimizes the thermo-mechanical design, opening a way to manage the growing trend of increasing power density of the front-end electronics. A novel technique for incorporating self-sealing micro-channels in the back of circuit chips has been demonstrated and is described. (NSS) Synchrotron Radiation and FEL Instrumentation NPO2-100, Evaluation of CdTe Pixel Detector with 3-Channel Window Comparator H. Toyokawa1, T. Hirono1, S. Wu1, M. Kawase1, M. Sato2, K. Kajiwara2, T. Miyazawa2, A. Suenaga3, H. Ikeda4 1

Controls and Computing Division, Japan Synchrotron Radiation Research Institute, Hyogo, Japan Industrial Application Division, Japan Synchrotron Radiation Research Institute, Hyogo, Japan 3 Howa Sangyo Co., Ltd., Tokyo, Japan 4 Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Kanagawa, Japan 2

X-ray single-photon counting pixel detectors have become the most powerful instrument in storage ring synchrotron light sources. We have been developing CdTe pixel detectors based on the hybrid pixel detector technology. CdTe is a promising semiconductor material for high energy X-ray detection, because the high atomic number (ZCd = 48, ZTe = 52) gives a high quantum efficiency and the large band-gap energy (Eg = 1.44 eV) allows operation at room temperature. CdTe sensors are generally fabricated with a metal/CdTe/metal structure. The front side was deposited with aluminum to form pixelated electrodes of 170 μm x 170 μm in size and 200 μm x 200 μm in pitch. The back side (X-ray irradiation side) was covered with a single platinumelectrode. This electrode configuration of Pt/CdTe/Al-pixel has the advantage of providing a high Schottky barrier formed on the Al/CdTe interface, and, hence, a benefit to operate the CdTe as an electron-collecting pixelated diode. In order to cope with the above mentioned CdTe detector, SP8-03 ASIC has been designed with a pixel size of 200 μm x 200 μm and a matrix of 20 x 50. Each pixel has a preamplifier, shaper, 3channel window comparator and 24-bit counter which is so designed as to be separated into 3 parts by a command to the ASIC. This architecture could realize a simultaneous measurement over multi-wavelength of X-rays. This presentation describes evaluation of analog circuit performance and demonstrates the measurement method of simultaneous multi-wavelength acquisition with the pixelated CdTe detector. NPO2-101, Development of CdTe Strip Sensor Assembled on Charge-Signal Readout Interposer Board M. Kawase1, H. Toyokawa1, T. Hirono1, S. Wu1, M. Sato2, K. Osaka2, T. Matsumoto2, A. Suenaga3, H. Ikeda4 1

Controls and Computing Division, Japan Synchrotron Radiation Research Institute, Hyogo, Japan Industrial Application Division, Japan Synchrotron Radiation Research Institute, Hyogo, Japan 3 Howa Sangyo Co., Ltd., Tokyo, Japan 4 Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Kanagawa, Japan 2

CdTe is a promising semiconductor material for high energy X-ray detection, because the high 413

atomic number (ZCd = 48, ZTe = 52) gives an excellent quantum efficiency and the large band-gap energy (Eg = 1.44 eV) allows operation at room temperature. We have been developing CdTe pixel and strip detectors for high energy X-ray diffraction experiments at SPring-8. As far as concerning a silicon-based detector, it is commonly employed a flip-chip bonding technique for a pixel detector, and a wire-bonding technique for a strip detector, respectively. While the CdTe pixel sensor could borrow the flip-chip bonding technique to directly connect to an ASIC, the CdTe strip sensor couldnt employ the wire-bonding technique because the CdTe crystal easily gave due to mechanical stress during the bonding procedure. In our technical choice the CdTe strip sensor was once bump-bonded to an interposer board with an In/Au-stud bonding method, and, then, the interposer board was wire-bonded to the ASIC. CdTe sensors employed here are fabricated with a metal/CdTe/metal structure. The front side was deposited with aluminum to form strip-shaped electrodes of 70 μm in width and 100 μm in pitch. The back side (X-ray irradiation side) was covered with a single platinum-electrode. This electrode configuration of Pt/CdTe/Al-pixel has the advantage of providing a high Schottky barrier formed on the Al/CdTe interface, and, hence, a benefit to operate the CdTe as an electroncollecting strip-shaped diode. The sensor assembly was adapted to the MYTHEN detector control board developed by PSI. This presentation describes evaluation of bonding quality and demonstrates the measurement as a powder diffractometer detector. NPO2-102, Simultaneous Fast Scanning Quadrimodal X-Ray Tomography at SOLEIL K. Medjoubi1, A. Bonissent2, N. Leclercq1, F. Langlois1, P. Mercere1, A. Somogyi1 1 2

Synchrotron SOLEIL, Saint-Aubin, France CPPM, Aix-Marseille Universit and CNRS/IN2P3, Marseille, France

Hard X-ray nanoprobe imaging provides a unique tool for probing specimens with high sensitivity and large penetration depth. Moreover, the combination of four complementary techniques such as X-ray fluorescence, absorption, phase contrast and dark field imaging gives complete quantitative information about the sample structure, composition and chemistry. The multi-technique fast FLYSCAN data acquisition scheme involving high through-put detectors has been developed at Synchrotron SOLEIL [1] and makes scanning tomography techniques feasible in a time-frame well-adapted to typical user experiments. Fast scanning quadrimodal 2D/3D imaging experiments have been performed at SOLEIL. We will present several examples illustrating the high performances of the FLYSCAN architecture. This innovative fast scanning scheme will be implemented at the Nanoscopium beamline for large field of view 2D and 3D multimodal scanning imaging. NPO2-103, A MTCA.4 Clock and Control System for the EuXFEL 2-D Detectors: Final Hardware and Firmware E. Motuk, M. Warren, M. Wing Department of Physics and Astronomy, University College London, London, UK

The final version of the clock and control (CC) system for the EuXFEL megapixel detectors has been produced. The system consists of the final version of the CC Rear Transition Module (RTM) and the second version of the DAMC2 AMC board. This paper presents the final hardware in 414

detail and describes the tests done to show the improved functionality of the system compared to the previous version. Furthermore, the firmware for the final CC system which integrates to the Front end electronics (FEE), the EuXFEL veto system, the timing system and the software control system is described in detail. The paper concludes with the plans for the initial system integration tests. NPO2-104, Response of the CVD Single Diamond Detector for 8GeV Electron Beam T. Shimaoka1, R. Satake1, J. H. Kaneko1, H. Aoyagi2, D. Miyazaki1, T. Aoki2, K. Fukami2, S. Suzuki2, C. Mitsuda2, A. Chayahara3, S. Shikata3 1

Graduate school of engineering, Hokkaido University, sapporo,Hokkaido, Japan JASRI/SPring-8, Hyogo, Japan 3 Institute of Advanced Industrial and Science Technology, Tsukuba,Ibaraki, Japan 2

In SPring-8/XFEL facility, interlock system has been developed to protect the permanent magnets of undulators; it was expected that electron irradiation resulted demagnetization. Diamond detector has excellent physical properties e.g., high radiation hardness, heat resistance, insulation and small detector size. Polycrystalline CVD diamonds used to develop halo monitor based on technique of X-ray beam position monitors in Spring-8 by Aoyagi et al. However, polycrystalline diamond has problems such as degradation of pulse heights due to charge trap caused at grain boundaries and defects in crystal. In this study, a CVD single crystal diamond with high charge carriers transportation was synthesized and fabricated into a detector. Response for 8GeV electron beam was studied. Study was conducted at the beam dump of the 8GeV Spring-8 booster synchrotron to measure response of the detector for 8GeV electrons. Fast time response of 0.35 nsec in FWHM, and pulse height of 0.5 V, i.e., 4x10-12C/pulse were obtained for CVD diamond with 100 micro meter thickness and whose charge collect efficiency was nearly 100%. Linearity between pulse height and injected beam current was kept from 104 to 106 electrons/pulse. NPO2-105, Calibration of the Non-Linear System Response of Prototypes of the DSSC Detector for the European XFEL G. Weidenspointner1,2, R. Andritschke1,2, D. Moch1,2, M. Porro1,2, S. Schlee1,2, S. Aschauer3, F. Erdinger4, P. Fischer4, M. Kirchgessner4, J. Soldat4, K. Hansen5 1

HLL MPG, Muenchen, Germany MPE, Garching, Germany 3 PNSensor, Muenchen, Germany 4 Universitaet Heidelberg, Heidelberg, Germany 5 DESY, Hamburg, Germany 2

The DSSC (DEPFET Sensor with Signal Compression) is a new instrument with non-linear compression of the input signal in the sensor and with parallel signal processing (filtering, linear amplification, and digitization) for all pixels. The DSSC will serve as 2d imaging detector at the European XFEL (X-ray Free Electron Laser) currently under construction in Hamburg, Germany. The DSSC design goal is to achieve at the same time single photon detection and high dynamic range of about 10,000 photons, both for photon energies down to 0.5 keV and read-out speeds up to 4.5 MHz. Realization of this goal requires an accurate calibration of the non-linear system response (NLSR) over the full dynamic range of the detector for each of the 1024 * 1024 DSSC 415

pixels. We present experimental NLSR calibrations of two DSSC prototype set-ups, each making use of the MM3 prototype read-out ASIC. With one set-up, we have for the first time performed a simultaneous NLSR calibration of multiple pixels, specifically of all seven pixels of the available thick oxide prototype DEPFET sensor. With the other set-up, we have achieved for the first time a NLSR calibration of a single pixel of a prototype DEPFET sensor in final DSSC thin oxide technology. NPO2-106, Highly Robust, High Iintensity White Synchrotron X-Ray Beam Monitor M. Kocsis, P. Berkvens, E. Bruer-Krisch, A. Bravin, T. Brochard, C. Nemoz, M. Renier, P.-H. Fournier, F. Esteve European Synchrotron Radiation Facility, Grenoble, France

Microbeam Radiation Therapy (MRT) uses highly collimated, quasi-parallel arrays of X-ray microbeams of 50-600 keV, produced by 3rd generation synchrotron sources. Among the MRT instrument components, the IC0 white X-ray beam monitor serves to measure the dose rate in the white synchrotron beam during the MRT irradiation. This device is essential for MRT clinical application. We constructed an extremely robust yet simple and reliable beam monitor. The device is based on a vacuum isolated Compton diode and is naturally UHV vacuum compatible. The device was subjected to a series of rigorous acceptance and characterisation test. These tests are very promising and predetermining the device as an IC0 monitor for the future clinical MRT application. NPO2-107, An Energy Dispersive Bent Laue Monochromator for K-Edge Subtraction Imaging N. Samadi1, Y. Zhu1, D. Chapman2 1 2

Biomedical Engineering, University of Saskatchewan, Saskatoon,Saskatchewan, Canada Anatomy and Cell Biology, University of Saskatchewan, Saskatoon,Saskatchewan, Canada

K-Edge Subtraction (KES) is a powerful synchrotron imaging method that allows the quantifiable determination of a contrast element (i.e. iodine) and matrix material (usually represented as water) in both projection imaging and computed tomography. With living systems, a bent Laue monochromator is typically employed to prepare imaging beams above and below the contrast element K-edge which focus at the subject location and subsequently diverge onto a detector. Conventional KES prepares the two beams by utilizing a splitter that blocks approximately 1/3 of the vertical beam size to prevent edge crossing energies beyond the monochromator. The use of a splitter forces the above and below K-edge imaging beams to cross at an angle which can cause a crossover artifact due to the different paths of the two beams. This crossover effect is most noticeable at the edges of highly absorbing objects, such as ribs in human coronary angiography. A bent Laue monochromator has been developed that has very good focal and energy dispersive properties for KES. With a 5mm vertical incident beam from a Canadian Light Source bend magnet, the vertical splitter size that blocks the edge crossing energies is less than 200 microns at the monochromator location. This makes the design and mounting of a splitter impractical from a mechanical and thermal loading perspective. Since approximately 4% of the vertical beam profile is involved in edge crossing energies, no splitter is employed. Also, the beam can be narrowed vertically allowing a smaller crossover angle than a splitter based system which minimizes crossover artifacts. The principle of operation of the monochromator, the experimental 416

arrangement for the system, and the effects of differing vertical incident beam sizes will be discussed. The combination of good spatial resolution, energy dispersive properties, flux and a unique approach to data analysis make this system nearly ideal for KES. NPO2-108, Laboratory Infrastructure for Detector Calibration and Characterization at the European XFEL J. Sztuk-Dambietz, S. Hauf, A. Koch, M. Kuster, M. Turcato European XFEL GmbH, Hamburg, Germany

The European X-ray Free Electron Laser (XFEL.EU) will provide as-yet-unrivaled peak brilliance and ultra-short pulses of spatially coherent X-rays with a pulse length of less than 100 fs in the energy range between 0.25 and 25 keV. The variety of scientific applications and especially the unique XFEL.EU time structure require adequate instrumentation to be developed in order to exploit the full potential of the light source. To make optimal use of the unprecedented capabilities of the European XFEL and master these vast technological challenges, the European XFEL GmbH has started a detector R&D program. Accurate calibration and characterization of the different detectors as well as development of user-friendly procedures and tools to re-do calibration during the XFEL.EU operation phase are very important for the success of the project. Therefore, in parallel to the detector development, the XFEL.EU detector group is building up the dedicated laboratory test infrastructure needed for fully assembled detectors, detector modules and/or sensor tiles which can be used during the start-up phase of the project and during the operation phase of the European XFEL facility. The current status of the laboratory detector test infrastructure as well as the future plans will be presented. NPO2-109, Electron Injection in Multi-Linear Silicon Drift Detectors A. Castoldi1, C. Guazzoni1, D. Mezza1, L. Chang1, R. Hartmann2, L. Strueder2,3 1

Politecnico di Milano and INFN, Milano, Italy PNSensor GmbH, Munich, Germany 3 Universitt Siegen, Siegen, Germany 2

Multi-Linear Silicon Drift Detectors (ML-SDDs) are a recent evolution of silicon drift detectors for position sensing and low-noise spectroscopy. The multi-linear transport mechanism based on electrons drift accounts for a relevant reduction in the number of channels required for true 2D position sensing and on chip JFETs allows the full exploitation of the small anode capacitance ( 2.5). The least amount of absorbed dose required to achieve these criteria was defined as the detection limit. This value was found to be 0.0837 cGy for a 2 cm brain tumor imaged a single germanium detector using 6 equally spaced angles from 0 to 180 degrees with 20 projections per angle and 0.5 million neutrons per projection. The SNR for the combination of phosphorus, sulfur, and iron with the given condition was 9.288 and FWHM for the iron with the given condition has the 0% error (20 mm FWHM). In conclusion, NSECT is capable of imaging a 2 cm brain tumor using its elemental composition phosphorus, sulfur, and iron and achieve acceptable SNR and FWHM. M13-25, Analytic Modeling of Energy-Absorption Response Functions Including Charge Transport Considerations in Photoconductor-Based X-Ray Detectors S. Yun1, H. K. Kim1,2, H. Youn1, J. Tanguay3, I. A. Cunningham3 1

School of Mechanical Engineering, Pusan National University, Busan, Korea Center for Advanced Medical Engineering Research, Pusan National University, Busan, Korea 3 Imaging Research Laboratories, Robarts Reserach Institute, London, Canada 2

The absorbed energy distribution (AED) in x-ray imaging detectors is an important parameter that affects both energy resolution and image quality through the Swank factor and detective quantum efficiency. Analytic expressions for x-ray interaction AED describing an escape of characteristic photons following photoelectric absorption and Compton scatter photons have been introduced previously by the authors. We have extended analytic models to include secondary quanta transport properties associated with detector materials. The model includes the effects of random conversion gain, depth dependent incomplete charge collection and charge sharing properties to describe the AED for photoconductor-based imaging detectors. We are in the progress of using Monte Carlo simulations and experiments using a CdTe pixel detector to validate the analytic approaches for transport properties. We believe this extended model gives more practical AED for pixel imaging detectors and will be useful for correcting spectral distortion artifacts commonly observed in photon-counting applications and evaluating the imaging performance of novel x-ray convertor materials. M13-26, Numerical Investigation of a Non-Interferometric Grating-Based X-Ray Imaging System R. Zhang1,2, L. Zhang1,2, Z. Chen1,2 1 2

Engineering Physics, Tsinghua University, Beijing, China Key Laboratory of Particle & Radiation Imaging, Ministry of Education, Beijing, China

Grating-based X-ray imaging can be grouped into two categories: interferometric and non594

interferometric. Interferometric setup, i.e. Talbot-Lau interferometer, has been intensively investigated in the recent past. In order to increase the angular sensitivity, gratings with very small period are preferred, while the fabrication of such gratings remains a challenging task. Another obstacle for the interferometric setup is the degradation of visibility when using broadband X-ray sources, especially when operated at high Talbot orders. Non-interferometric setup attempts to use large period gratings and a projection geometry. In this paper, we investigate the impact of several factors (grating period, inter-grating distance and X-ray spectrum) on the performance of the system using wave optics simulations. In particular, we focus on the visibility of the phase stepping curve, as it largely determines the ability of the system to retrieve phase and dark-field information. Based on the simulation results, we discuss the design aspects and limitations of the non-interferometric setup. M13-27, An Approach to System Optimization for X-Ray Photon-Counting Systems Using Performance on a Detection/Localization Task Y. Lu1, H. Zhang2, Z. Liang3, G. Gindi3 1

Electrical Engineering, Stony Brook University, Stony Brook, NY, US Biomedical Engineering, Stony Brook University, Stony Brook, NY, US 3 Radiology, Stony Brook University, Stony Brook, NY, US 2

We address the problem of optimizing data acquisition for photon-counting CT. We formulate a task-driven approach using a clinically relevant task of detection and localization of a lesion in a search region. A lesion is considered successfully detected and localized if an observer concludes that a lesion is, in fact, present and the estimated location of the lesion lies within a pre-specified search tolerance radius of the true lesion. The appropriate scalar measure of task performance is ALROC, the area under the LROC curve. The LROC curve measures probability of correct detection/localization vs. the false positive rate as a detection threshold is swept. For hardware optimization, the observer performing the task should operate on the raw (sinogram) data so that the best possible information, independent of the parameters of any particular reconstruction algorithm, is collected. To carry out the task, we use the ideal observer (IO), a numerical observer that yields the maximal ALROC amongst all observers. This differs from the usual numerical observer that operates on the reconstructed data and is designed so that its performance tracks that of a human observer. So while the optimization is carried out in the sinogram domain, the task definition is in the object domain. In previous work we formulated the general ideal observer for the detection/localization task. In this work, we mathematically specialize this IO to the case of photon-counting transmission tomography. We applied the IO to a 2D simulation of CT with the task of detecting a 3mm lung nodule in a lung region of a 512x512 phantom. The application was to optimize the number of angular acquisitions given a fixed dose. A plot of ALROC vs. angle number peaks at 42 angles. We also plotted ALROC vs. dose (at 105 angles) to characterize the increase in task performance with count level. We continue to explore the complex tradeoffs in CT acquisition for this clinically significant task. M13-28, The Simulation of a Fast Fan-Beam Dual-Energy X-Ray Absorptiometry for Forearm L. Li, C. Li, Z. Chen Department of Engineering Physics,Tsinghua University, Beijing, China

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Social population ageing has given rise to the number of patients with osteoporosis. Compared with current dual energy X-ray absorptiometry (DEXA) for total body, spine or hip, the DEXA for the forearm which is a preferred site in bone general physical examinations is rare and cannot meet our cost-effective requirements. We propose a new cost-effective fast wide fan-beam DEXA for the forearm, the result of which can be used in conjunction with the clinical risk factors as an aid to the physician in diagnosis of osteoporosis. In our system, we utilize the fan-beam of about 20 degrees, so that the angle can almost completely cover, even exceed the width of adults forearm. As a result, its possible to obtain one cross-sectional image via single exposure, rather than traditional zigzag scanning, hence increasing the measuring speed. This paper simulated and analysis the two typical dual energy measurement configuration: dual-layer detector technique and x-ray source KV-switching technique. Our goal is to find a DEXA configuration with better spectral separation and enough photons in both low and high energy data. Simulations show that a copper filter is necessary for both dual-layer detector and KV-switching DEXA. Although the spectral separation of the dual-layer detector of GOS/Cu+CsI is not bad, the photons reached the high energy detector are reduced too much. The KV-switching mode with a copper filter can provide both good spectral separation and enough photons. Thus, not only the accuracy of BMD (Bone Mineral Density, g/cm2) and BMC (Bone Mineral Content, g/cm) is improved, but also the quality and SNR of the high-energy image increase significantly in this system. M13-29, A Software Tool for on Field Spectrometry of Diagnostic X-Ray Beams L. Andreani1,2, M. Bontempi3,4, P. L. Rossi2, L. P. Rignanese2, M. Zuffa1, G. Baldazzi1,2 1

Div. of Bologna, INFN, Bologna, Italy Dept. of Physics and Astronomy, University of Bologna, Bologna, Italy 3 Laboratorio NaBi, Istituto Ortopedico Rizzoli, Bologna, Italy 4 Centro Fermi, Roma, Italy 2

Conventional radiology uses X-ray beams with polychromatic spectrum consisting of a bremsstrahlung continuous component - with an energy band known only by means of filtration and kVp values - and some fluorescence lines. The spectrum knowledge however, would be a fundamental requirement to optimize the imaging quality over dose administered to the patient ratio. Because of the difficulty to make spectrometry directly on the available diagnostic beam (the anode brilliance is always too great for any spectrometric detector) we made a new detection system, that together with a simulation software based on a parametric equation system is capable to perform the spectrometry of the beam. Simultaneously, a PC performs the reconstruction of the spectrum starting from the X-ray beam parameters detected. The goal of this work is to obtain a low-cost instrument, easily installable on almost all the radiologic apparatus, capable to provide immediately the spectrum of any diagnostic exposure. This will allow to build composed filters to limit the energy bandwidth for low-dose better imaging and to register data on a patient dosimetric smart card. The software tool, capable to reconstruct an X-ray diagnostic beam spectrum from 10 keV to 150 keV, using experimental parameters, will be described and discussed. Also, the experimental validation of the software will be illustrated. M13-30, Integrating a Three-Dimensional Spatiotemporal Glioma Model with a PET Simulation System to Create Patient-Specific FMISO Images R. L. Harrison1, J. Jacobs2, B. F. Elston1, A. M. Alessio1, D. Byrd1, R. C. Rockne2, A. Hawkins-Daarud2, M. Muzi1, P. R. Jackson2, K. R. Swanson2, P. E. Kinahan1

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1 2

Radiology, University of Washington, Seattle, Washington, USA Swanson Lab, Northwestern University, Chicago, Illinois, USA

A problem in the management of gliomas is a lack of methods that allow clinicians to determine if therapeutic interventions are having any impact on tumor progression. We are developing a method to predict FMISO PET images of evolving, untreated glioma tumors. These patientspecific simulations can be compared to post-treatment images to provide a measure of the impact of therapy. Methods We use as a starting point three-dimensional maps of the uptake of the PET tracer 18F-Fluoromisonidazole (FMISO) in gliomas, which is generated using output of our PIHNA model (proliferation, invasion, hypoxia necrosis and angiogenesis). The FMISO distribution is used as an input into our analytic PET simulator (ASIM) to generate fully-3D sinograms with confounding effects: sinogram PSF blurring, attenuation, estimates of random and scattered coincidences, and Poisson noise. An attenuation map was calculated by segmenting the BrainWeb atlas used by PIHNA to generate the FMISO uptake distribution. Noise levels were matched to typical patient acquisition protocols. The sinograms were then reconstructed using the same reconstruction algorithm (either 3DRP or OSEM) and parameters as the patient images. Results The simulated FMISO-PET images are not identical to the measured images, but have similar qualitative and quantitative characteristics. Qualitative evaluations include noise level, noise texture, resolution. Quantitative characteristics include tumor location, extent, and level of FMISO uptake. Conclusion We have integrated a PET simulation system with a three dimensional spatiotemporal glioma model to create patient-specific FMISO images. While our simulation and methods for using it are evolving, these preliminary results show a promising similarity between data generated by the simulation and actual patient images. M13-31, Characteristics of Bremsstrahlung Emissions from Radionuclide Therapy Isotopes C. F. Uribe1, P. L. Esquinas1, H. Piwowarska-Bilska2, D. Pawlak3, R. Mikolajczak3, B. Birkenfeld2, A. Celler1 1

Radiology and Physics & Astronomy, University of British Columbia, Vancouver, B.C., Canada Nuclear Medicine, Pomeranian Medical University, Szczecin, Poland 3 National Centre for Nuclear Research, Radioisotope Centre POLATOM,, Otwock, Poland 2

Targeted radionuclide therapies (TRT) require accurate imaging studies to verify radiotracer distributions and to estimate doses delivered to tumours and normal organs. However, bremsstrahlung (BRS) photons generated by beta emissions of radioisotopes used in TRT are difficult to image and quantitate. Extensive simulation studies have been performed using two Monte Carlo programs, GATE and MCNP. Their objective was to investigate the characteristics of BRS of beta emitters that are used in TRT to better understand the effects observed in imaging studies and to provide guidance to improve quantitative accuracy of imaging acquisitions. Small sources emitting monoenergetic electrons, as well as small containers filled with 90Y, 188Re, and 177 Lu were simulated. Additionally, imaging studies performed using two commercial gamma cameras with 3 different collimators were simulated and the components of the spectra were analyzed. Finally, a series of experiments with sources placed in a large water phantom were performed and the shapes of simulated and experimentally acquired spectra and the corresponding images were compared. The results of simulations have shown that the total BRS yield (number of gammas per electron) was low and the shapes of the spectra obtained from both programs are very similar, although MCNP creates more photons at energies below 50keV. Larger discrepancies occurred in BRS produced by different radioisotopes. Analysis of the imaging spectra showed that our simulations 597

reproduce the shapes of the spectra for all collimators quite well. Since the LEHR collimator is more transparent to high energy photons, large background from scattered BRS photons dominates low energy spectra. The use of ME and HE collimators improves spectrum characteristics. The cleanest spectra were obtained with HE collimators; however, image resolution for this case still needs to be investigated. M13-32, Effect of Noise Level, Administered Activity and Body Habitus on Detection of Renal Function Defect in Pediatric Diagnostic Imaging of 99mTc-Dimercaptosuccinic Acid T.-S. Lee1, W. E. Bolch2, S. T. Treves3, G. Sgouros1, E. C. Frey1 1

Radiology, Johns Hopkins University, Baltimore, MD, USA Biomedical Engineering, University of Florida, Gainesville, FL, USA 3 Radiology, Boston Childrens Hospital, Boston, MA, USA 2

Radiation dose is of special concern in pediatric patients for higher sensitivity in radiation and longer timeframe to manifest stochastic effects. Since body habitus can affect image quality in pediatric patients, it is important to understand the tradeoff between image quality, radiation dose, and body habitus. In this study, B-spline based mathematical phantoms were used to simulate the anatomy of two 10-year old girls having the same weight but different body habitus. Literature data was used to obtain organ uptakes of 99mTc-dimercaptosuccinic acid. Projection data for administered activities (AA) ranging from 0.25 to 1.5 times a standard AA were simulated using an analytic projector modeling attenuation, scatter, and the collimator-detector response followed by simulation of Poisson noise. Kidney function defects were created at several locations in each kidney with varying activity concentration ratios. The projections were reconstructed using filtered-backprojection (FB) followed by 3D Butterworth filter with various cutoff frequencies to find an optimal cut-off frequency. Channelized Hotelling observer and receiver operating characteristics (ROC) methodologies were applied to the reconstructed images for the task of defect detection. Areas under the ROC curve (AUC) were computed to assess the changes in the lesion detection. At higher, non-optimal cutoffs results showed different trade-offs for the lesion detectability between the 2 phantoms indicating that body habitus, and not just weight, is a significant factor in determining image quality for a given AA. However, use of the optimal cutoff resulted in little difference in the image quality versus AA tradeoff for the two phantoms. A population of phantoms spanning the range of pediatric height has been generated and the results of this study will ultimately be extended to the full population in order to provide data needed to establish optimal pediatric dosing guidelines. M13-33, A Realistic Digital Phantom for Perfusion C-Arm CT Based on MRI Data A. Aichert1,2, M. Manhart2, B. K. Navalpakkam2, R. Grimm2, J. Hutter2, A. Maier2, J. Hornegger2, A. Doerfler1 1 2

Department for Neuroradiology, Universitaetsklinikum Erlangen, Erlangen, Germany Pattern Recognition Lab, Friedrich-Alexander-Universitaet Erlangen-Nürnberg, Erlangen, Germany

We present a digital 4D brain perfusion phantom for the evaluation of reconstruction algorithms, particularly those using non-linear regularization for perfusion CT and perfusion C-arm CT. It relies on real MRI data to create a dense physiological brain model based on indicator-dilution theory. The phantom is complemented by cortical bone as estimated from dedicated MR sequences. Patient motion can be simulated as small rotations in the sagittal plane. The realism of 598

this phantom is reflected in its ability to mimic streak artifacts in its reconstructions which are often encountered in clinical practice. The phantom enables a more realistic evaluation of reconstruction algorithms than with previously published phantoms, because the most practical reconstruction algorithm for perfusion measurement is determined the ability to handle artifacts, particularly streaks. MATLAB scripts to create a 3D-time-series of the phantom are freely available for download, which allows researchers to create their own projection data for arbitrary protocols and simulated hardware. The phantom is flexible with respect to the amount of noise, the location and severity of the simulated stroke, as well as the introduction of patient motion to simulate streak artifacts.

***************** M14 (8)******************************* M14 New Detector Materials and Technologies / SPECT Instrumentation Friday, Nov. 1 08:00-10:00 GBR 101-102 Session Chair: Suleman Surti, University of Pennsylvania, United States; Scott Metzler, University of Pennsylvania, United States

(08:00) M14-1, Beta-Particle Digital Autoradiography with the iQID Camera B. W. Miller1, J. Orozco2,3, A. Kenoyer2, D. R. Fisher1, M. Bliss1, L. R. Furenlid4, D. K. Hamlin5, D. S. Wilbur5, E. Balkin5, M. D. Hylarides2, B. M. Sandmaier2,3, O. W. Press2, J. M. Pagel2,3 1

Pacific Northwest National Laboratory, Richland, WA, USA Fred Hutchinson Cancer Research Center, Seattle, WA, USA 3 Department of Medicine, University of Washington, Seattle, WA, USA 4 Center for Gamma-Ray Imaging, The University of Arizona, Tucson, AZ, USA 5 Department of Radiation Oncology, University of Washington, Seattle, WA, USA 2

Beta emitters have shown to be an effective treatment strategy for cancer therapy. For example, Yttrium-90 is a well-accepted, high-energy (2.2 MeV beta) medical isotope with outstanding physical properties for both cell-directed radioimmunotherapy and intra-tumoral radiation therapy. Researchers need capabilities and tools that provide visualization and quantification for assessing the local biodistribution of beta emitters. We present a novel digital autoradiography camera that enables assessment of beta-emitter biodistribution in real time. The iQID (ionizing-radiation Quantum Imaging Detector) camera is sensitive to a broad range of ionizing radiation including gamma/X-rays, alphas, betas, and neutron particles. Ionizing radiation is imaged on an event-byevent basis at high resolution, and an image of a source distribution is constructed in real time using high-performance graphics processing hardware and software. Additional features of the iQID camera include portability, large detector areas, excellent spatial resolution, high sensitivity, and temporal information for each particle. We will discuss iQID beta-particle detection methods, initial digital autoradiography imaging results, and spatial-resolution challenges and opportunities. (08:15) M14-2, Performance of a Novel, Small-Cell, High-Fill-Factor SiPM for TOF-PET 599

C. Piemonte, A. Ferri, A. Gola, N. Serra, A. Tarolli, N. Zorzi FBK, Trento, Italy

In this contribution, we present a novel technology, developed at FBK, for the production of SiPMs with very high fill factor, called RGB-HD (red-green-blue high-density SiPM). The first prototypes feature a cell size of 15x15μm2 and 30x30μm2 with nominal fill factors of 48 % and 75 %, respectively. Here we focus on the 30 μm cell size, which has been used to produce a 4x4mm2 SiPM. Several samples have been coupled to 3x3x5 mm3 LYSO as well as Ce:GAGG scintillator crystals, in order to prove their performance in TOF-PET application. The results are extremely promising. We have measured energy resolution of 9 % and coincidence resolving time of 130 ps FWHM with LYSO and 7 % and 280 ps FWHM with Ce:GAGG. (08:30) M14-3, Effects of DCR, PDP and Saturation on the Energy Resolution of Digital SiPMs for PET L. Huf Campos Braga, M. Perenzoni, D. Stoppa Fondazione Bruno Kessler (FBK), Trento, Italy

In this paper, we use the SPADnet-I sensor, a fully digital 8x16 SiPM array with per-SPAD SRAMs, to analyze the effects photon detection efficiency (PDE), dark count rate (DCR) and saturation on the energy resolution of PET systems. We show that the mini-SiPM compression schemes of SPADnet-I result in a total photon loss of about 6% for a 511 keV gamma LYSO scintillation. The behavior of the sensor energy resolution with respect to variations in PDE and DCR is measured and modeled. The optimum operation point is found to be at circa 8% of the high-DCR SPADs disabled, resulting in 10.9% energy resolution. Moreover, from the described model, we show that integrating per-SPAD SRAMs on-chip actually has a negative effect in the sensor energy resolution due to the reduced fill-factor. Finally, we show that below a certain level of DCR, the optimum operation point shifts to 100% of the SPADs enabled, completely eliminating any gains from integrating per-SPAD SRAMs. (08:45) M14-4, Line-Spread Function and Noise Spectrum Analysis of a Direct-Detection X-Ray CMOS Image Sensor with 500 μm Thick High Resistivity Silicon T. Hatsui1,2, S. Ono1, M. Omodani2, T. Kudo1, K. Kobayashi1,2, Y. Kirihara1 1 2

SPring-8 Center, RIKEN, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan JASRI, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan

A direct-detection X-ray CMOS image Sensor with 500 um Thick High resistivity silicon has been developed for scientific applications at X-ray Free-electron Laser Facility, SACLA. The full depletion of 500 um thick silicon was enabled by separating thick pn diode and CMOS layer by buried oxide. The sensor consists of 1.9 M pixels with 30 um pixel square shape. The single layer sensor give 40 % quantum efficiency at 20 keV X-ray photons. Multiple-layer stacking is also possible in order to increase the quantum efficiency. In order to access the X-ray imaging capability in other fields, especially, medical imaging, imaging performance was evaluated with X-ray source at 28 kV with Mo target through 0.03 mm thick Molybdenum and 2.0 mm thick Aluminum filters. (IEC6127 RQA M2). The line-spread function (LSF) shows full width half 600

maximum of 30 um, and resulting MTF stays 67% at 10 line/mm. The noise spectrum shows no peaks indicating that this sensor has high level of uniformity consistent with the sensor structure, where X-ray to electron conversion is carried out by high quality silicon wafer. (09:00) M14-5, Evaluation of a Compact, General-Purpose Germanium Gamma Camera D. L. Campbell1, E. Hull2, T. E. Peterson1 1 2

Institute of Imaging Science, Vanderbilt University, Nashville, TN, USA PHDs Co., Knoxville, TN, USA

Technological advances in High-Purity Germanium (HPGe) detectors have given rise to compact, mechanically cooled gamma cameras that do not require bulky liquid nitrogen dewars to operate. When used in the double-sided strip configuration, spatial resolution finer than the strip width can be obtained using pulse signal analysis for position interpolation. With 3D position sensitivity and the best energy resolution of any conventional detector (1% FWHM at 140 keV), HPGe detectors have many possible applications in biomedical imaging. We here introduce the Germanium Gamma Camera (GGC1.1), a fully integrated imaging system incorporating a 90-mm diameter, 10-mm thick germanium detector with 16 x 16 orthogonal strips of 5-mm pitch having 0.25-mm wide gaps between the strips. All data acquisition, system control, and system monitoring functions are accessed through a single USB-2.0 port. An integrated assembly also allows for interchangeable mounting of parallel-hole and pinhole collimators, whose designs were based on simulations for optimizing collimation for small-animal imaging. The intrinsic properties of the GGC1.1 detector system are measured according to the NEMA NU 1-2007 standards for gamma cameras, including detector efficiency, spatial resolution, energy resolution, and uniformity. In addition, we demonstrate the planar imaging capabilities of the GGC1.1 with the parallel-hole and pinhole collimators by scanning line sources, as well as a phantom comprised of spherical hot spots in a warm background. (09:15) M14-6, Preliminary Investigation of Imaging Properties for Sub-Millimeter SquarePinholes D. Xia1, M.-A. Park2, S. C. Moore2, S. D. Metzler1 1 2

Radiology, University of Pennsylvania, Philadelphia, PA, USA Radiology/Nuclear Medicine, Brigham & Women's Hospital and Harvard Medical School, Boston, MA, USA

Due to its excellent spatial resolution at reasonable sensitivity, single photon emission computed tomography has been widely used for small animal and organ imaging. Recently, pinhole collimators with square apertures have been proposed, allowing more efficient detector usage than for conventional pinholes with circular apertures. In this work, we designed and fabricated collimator inserts with square apertures of very small size using casting of a Pt/Ir alloy and conducted experiments to investigate the imaging properties of these inserts, including acceptance angle and sensitivity. By using a moving small source mimicking a flood, we have measured the projections of the field-of-view (FOV) of the inserts, from which the axial and transverse acceptance-angles have been calculated. The mean (standard deviation) of the axial and transverse acceptance angles are 36.3o (0.9o) and 32.7o(0.7o). These values agree well with the designed angles (axial: 34.3o, transverse: 29.9o). Moreover, we have measured the sensitivity at 7x7 601

different source positions within a plane parallel to the aperture's plane for a sampling of these inserts. The dependence of the insert sensitivity on incident angle has been also explored. A leastsquares fit to the sensitivity was made, assuming a sinxθ shape. The fitted exponent of the sine function and the sensitivity-effective diameter were 9.52 and 0.35 mm, respectively. In addition, to verify the sensitivity of the square-aperture insert, we have performed a Monte-Carlo simulation. For the simulated sensitivity data, the exponent of the sine function and the diameter of the simulated data were 7.78 and 0.38 mm, which are similar to our experimental measurements. In conclusion, the measured values are in reasonable agreement with the designed values, which shows the successful prototype production of casting small square aperture sizes with a rectangular FOV. (09:30) M14-7, Performance Characterisation of a Compact SPECT Detector Based on dSiPMs and Monolithic LYSO C. Bouckaert, K. Deprez, S. Espana, S. Vandenberghe, R. Van Holen MEDISIP - Ghent University - iMinds, Ghent, Belgium

Digital silicon photomultipliers (dSiPM) are compact, high-resolution photon detectors that might be useful as an MR-compatible alternative for current SPECT detectors. However, up until now the performance of these detectors was especially investigated for PET applications. The goal of this study was therefore to characterize the performance of dSiPMs in combination with monolithic LYSO scintillators as detectors for SPECT. We optically coupled a 2 mm thick monolithic LYSO scintillator crystal to the dSiPM and placed this setup in a fridge to avoid too high dark count rates during the measurements. First, a filter was developed to remove the dark counts generated by the detectors from the dataset. To validate the performance of this filter and the detector itself, we compared its sensitivity to the sensitivity obtained with a Hamamatsu H8500 position sensitive photomultiplier tube (PSPMT). We performed identical measurements using a 57Co source on both setups and compared the results. These tests showed that, even after applying the filter, the count rate of the dSiPM was comparable to that of the PSPMT. Next, we investigated the intrinsic detector resolution obtainable using these dSiPMs. We designed a tungsten collimator containing rods ranging from 1.4 mm to 0.3 mm. After irradiating this collimator with a uniform 99mTc source, the data were reconstructed using a maximumlikelihood positioning algorithm (MLP). In the resulting image, the 0.6 mm rods could easily be distinguished. Apart from this, we also calculated the mean detector resolution to be 0.71 mm based on the acquisitions used for the MLP calibration. Based on these results, it can be concluded that dSiPMs in combination with thin, monolithic LYSO scintillators can be used as detectors for SPECT. (09:45) M14-8, Artificial Compound-Eye Gamma Camera for SPECT Imaging X.-C. Lai, L.-J. Meng Nuclear, Plasma and Radiological Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA

In this work, we explore the use of use of artificial compound eye gamma camera (CEGC) for SPECT imaging. As we have demonstrated with a Monte Carlo study, a small animal SPECT 602

system based on the CEGC could achieve a photon detection efficiency of >1% (as compared to the typical levels of 0.1%-0.01% found in modern pre-clinical SPECT instrumentations), while maintaining an excellent spatial resolution. This dramatic increase in sensitivity could potentially provide a radical change in how we might employ SPECT imagining in both pre-clinical and (potentially) clinical practice, by offering a dramatically lowered detection limit and allowing for new imaging procedures that would be difficult to implement with the current generation of SPECT instrumentations. The design of compound-eye gamma camera (CEGC) is inspired by the compound eyes often found on small invertebrates, such as flies and moths. A CEGC consists of a large number of independent micro-pinhole-gamma-camera-elements closely packed in a dense array (e.g. 10-20 independent camera-elements per cm2). Each of the micro-camera-elements covers a narrow view angular through the object. When constructing a SPECT system with multiple CEGCs, there will be a very large number (up to several thousand) of micro-cameraelements in the system pointing towards the object and collecting gamma rays simultaneously. This is the key for attaining a super-high detection efficiency, while maintaining an excellent imaging resolution.

**************** M15 (8) ****************************** M15 Image Reconstruction II Friday, Nov. 1 08:00-10:00 GBR 103 Session Chair: Jinyi Qi, University of California, Davis, United States; Seungryong Cho, KAIST, South Korea

(08:00) M15-1, Constrained Nonconvex TpV-Minimization for Image Reconstruction with Extremely Sparse Projection View Sampling in CT E. Y. Sidky1, R. Chartrand2, X. Pan1 1 2

Radiology, University of Chicago, Chicago, IL, USA Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, USA

An iterative image reconstruction algorithm for exploiting sparsity in the gradient magnitude image (GMI) is presented for the purpose of obtaining images in computed tomography (CT) from very sparse projection view-angle sampling. The algorithm is designed to solve a non-convex optimization problem that encourages solutions to the CT imaging model with a high degree of sparsity in the GMI. It is often the case, for medical imaging, that the underlying structure of the subject matches well with this sparsity model, and we expect that the developed algorithm has high potential utility for CT devices with limited projection sampling. Results indicate substantial gains in undersampling compared with standard iterative algorithms, and significant improvements also when compared with convex total-variation minimization.

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(08:15) M15-2, A Non-Local Total Variation Constrained Reconstruction Method for Clinical Cone-Beam CT J. Hao1,2, L. Zhang1,2, X. Jin1,2, K. Kang1,2 1 2

Department of Engineering Physics, Tsinghua University, Beijing, China Key Laboratory of Particle & Radiation Imaging (Tsinghua University), Ministry of Education, Beijing, China

In this paper, we present a novel non-local total variation (NLTV) constrained method for clinical CT imaging. Compared with conventional TV method, it achieves much better results in structure preservation, especially in low-dose scans. The gradient in TV norm is calculated using two nearest neighbors of the target pixel; while all pixels are used as the neighbors in NLTV. In additional, the weights are spatially varying depending on the similarity between the neighborhoods of the targeting and neighboring pixels. We conducted simulation study and clinical experiments to demonstrate its advantages and effectiveness. The results show that it has better performance both in noise reduction and artifacts elimination, which is practical for clinical CT imaging. (08:30) M15-3, A Comparison Study of Total Variation Stokes Strategy for Low-Dose CT Image Reconstruction Y. Liu1, H. Lu2, K. Wang3, H. Zhang4, Z. Liang4 1

Departments of Radiology and Electrical and Computer Engineering, Stony Brook University, Stony Brook, USA Department of Biomedical Engineering, Fourth Military Medical University, Xi'An, Shanxi, China 3 Departments of Applied Mathematics and Statistics, Stony Brook University, Stony Brook, USA 4 Departments of Radiology, Stony Brook University, Stony Brook, USA 2

Previous works have demonstrated that the CT images could be reconstructed by minimizing the total variation (TV) or the case adaptive weighted total variation (AwTV) of the desired images. However, the results are reported to suffer from the undesired patchy artifacts or stair-case effects. In our previous work, we found that these drawbacks could be eliminated by using a novel method total variation stokes (TVS) method for CT image reconstruction from both sparse-view and lowmAs data in our clinical data study. In order to further validate the performance of the TVS method compared to adaptive steepest descent-projection onto convex set (ASD-POCS) and AwTV-POC methods, two phantoms: shepp-logan digital phantom and Catphan 600 physical phantom were used for simulation study. From the results, we can observe that the patchy artifacts were efficiently suppressed in the uniform area. In addition, the edges were also well preserved by TVS method compared to the other methods. Besides the visualization-based comparison, quantitative evaluation merits were also studied in this paper. The universal quality index (UQI) study indicated the TVS method is more likely to produce a result closed to the true image. More evaluation merits on the performance of the TVS method, such as convergence study and fullwidth-at-half-maximum (FWHM) are under progress. (08:45) M15-4, Low-Dose Limited View 4D CT Reconstruction Using Patch-Based Low-Rank Regularization K. S. Kim, J. C. Ye

604

Bio and Brain Eng., Korea Advanced Institute of Science and Technology (KAIST), Daejeon, South Korea

Dynamic 4D x-ray computed tomography (CT) is often used for several applications such as perfusion imaging, cardiac imaging and radiotherapy. To acquire enough data for several phases, repeated x-ray CT scans should be conducted, so the radiation exposure increases. Thus, the dose reduction is an important issue for dynamic CT scans. Dose reduction can be conducted by reducing views or the x-ray tube current, which results in reconstruction quality degradation. Here, we develop a novel dynamic 4D CT reconstruction technique to overcome such limitation by exploiting the temporal redundancies from the adjacent frames. The idea comes from recent advances of patch-based signal processing that provides high performance denoising while preserving edge directions. In this paper, we extend such patch-based penalty within a reconstruction framework using a penalized maximum likelihood (ML) method. More specifically, we impose a patch-based low rank penalty between adjacent frames as well as within 3D volume to exploit the geometric similarity during reconstruction. The low rank constraint is used because the rank structures are relatively less sensitive to global intensity changes and more easy to capture the edge information. Here, the similarity patch groups are constructed, which are also refined during iteration such that the algorithm gradually improves the geometric constraint during reconstruction. In simulation, we compared conventional FDK and maximum likelihood method with the proposed method. Our proposed method using the patch-base low-rank penalty significantly improved the image quality while preserving edge directions. (09:00) M15-5, Metal Artifact Reduction Based on Multi-Level Sinogram Segmentation and Sequentially Applied MAP-EM Reconstruction Method U. Tuna, D. Us, U. Ruotsalainen Department of Signal Processing and BioMediTech, Tampere University of Technology, Tampere, Finland

High density objects in the field-of-view (FOV) are the primary reasons for the so-called metal artifacts in the field of medical imaging. The metal artifact reduction (MAR) methods intend to abate the effect of these highly attenuating materials in the reconstructed images. Before a reduction method is applied to the sinogram data, the bins affected from the metals need to be segmented accurately. In this study, we propose a new segmentation method which relies on multi-level segmentation method based on weighted Otsus threshold level. This new segmentation method also utilizes once image reconstruction and forward projection operations in order to segment out the pixels representing the metal objects in the image domain and their corresponding sinogram bins. The image reconstruction is performed using the recently published sequentially applied maximum a posteriori expectation maximization (MAP-EM) method with spatial domain median filtering. The sinogram bins affected from the metal objects can be regarded as the missing data. These missing sinogram bins are modeled in the system matrix. With the sequential application of the MAP-EM method, the undesired effect of the spatial domain regularization filter is minimized while the missing parts of the sinogram are estimated consistently. In the simulations, we used the numerical jaw phantom data with different amount of metal objects and Gaussian noise contamination. The promising preliminary results showed that the sinogram bins affected by the metal objects in the FOV can be segmented out accurately. Furthermore, near exact reconstructed images can be obtained using the sequentially applied MAP-EM method with median regularization.

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(09:15) M15-6, The Importance of the Statistical Assumption in Statistical X-Ray CT Image Reconstruction J. Xu, B. M. Tsui Radiology/DMIP, Johns Hopkins University, Baltimore, MD, USA

Statistical image reconstruction (SIR) is a promising approach to reducing radiation dose in clinical x-ray CT scans. CT signal follows a compound Poisson distribution, its probability density function (PDF) does not have an analytical form hence cannot be used in an SIR method. We investigated the effects of using an approximate statistical assumption (SA) in SIR methods for CT applications. We applied a pseudo ideal observer (pIO) to simulated x-ray CT projection data at different dose levels in a low contrast lesion detection task. The CT simulation modeled the polychromatic x-ray tube spectrum, the effects of the bowtie filter, and the energy-integrating detectors. The pIO used a pseudo likelihood function (pLF) to calculate the pseudo likelihood ratio, which was the decision variable used by the pIO to distinguish between the two classes, lesion absent and lesion present. The pLF was an approximation to the true LF of the underlying data. If the pLF coincided with the LF, the pIO reduced to the IO. Otherwise, the pIO had inferior performance than the IO; this performance difference quantified the closeness between the pseudo likelihood and the exact one. In our setting, the exact LF was the compound Poisson PDF of the CT projection data. Using lesion detectability as a figure-of-merit, our results showed that at down to 0.1% of a reference tube current level I0, the pIO that used a Poisson approximation, or a matched variance Gaussian approximation in either the transmission or the line integral domain, achieved 99% the performance of the IO. The constant variance Gaussian approximation had only 70%-80% the IO performance. At tube currents lower than 0.1%I0, the performance difference between pIO and IO is more substantial. We conclude that at down to 0.1% of the current clinical dose, it is important to account for the mean-dependent variance in the CT projection data in the SA, the exact PDF of the CT signal is not as important. (09:30) M15-7, MRI Guided Myocardial Perfusion PET Image Reconstruction J. Tang1, T. Doan1, W. Geng1, L. Lu2, A. Rahmim3 1

Oakland University, Rochester, MI, United States Southern Medical University, Guangzhou, Guangdong, China 3 Johns Hopkins University, Baltimore, MD, United States 2

Integrated whole-body PET/MRI provides opportunities to fully take advantage of simultaneously acquired anatomical and functional information. The purpose of this study is to incorporate the MR measured anatomical information in myocardial perfusion (MP) PET image reconstruction and to evaluate the performance. Using the 4D XCAT phantom, we simulated cardiac-gated MP PET imaging data with normal perfusion. A set of clinically acquired time activity curves representing the typical patient Rb-82 biodistribution was used in the analytical simulation. Noisy sinograms were generated with count levels comparable to patient measurement. Cardiac gated MR images were simulated using the SIMRI simulator, with the MR sequence specified to be 3D T1-weighted as used in a clinical PET/MRI protocol. For each cardiac gate, we applied the closedform maximum a posteriori (MAP) PET image reconstruction that takes the joint-entropy (JE) between the PET and corresponding MR image intensities as the prior. The JE was calculated based on non-parametric Parzen estimation of the probability density function. To save calculation 606

time, the JE prior was applied only to a rectangular volume covering the entire heart area. To quantitatively evaluate the reconstructed images from the JE MAP method, we created polar maps of the left ventricle. We divided the polar map into 5 segments and calculated the normalized mean square error (bias) and normalized standard deviation (noise) for each segment. On the whole polar map and its segments, the activity values estimated from the JE MAP algorithm showed significantly improved noise versus bias tradeoff compared to those from the conventional ML EM algorithm. To conclude, we adapted the anato-functional JE MAP reconstruction method to MP PET and demonstrated quantitative improvement of the reconstructed images with realistic simulation. This approach will have promising applications especially in the emerging integrated cardiac PET/MR imaging. (09:45) M15-8, TOF Versus Non-TOF PET for the Quantification of Cardiac Defects S. Mahmood1, K. Erlandsson2, D. R. McGowan3, D. Yatigammana4, H. Zolfagharinia4, R. Wise5, A. Divoli6, I. Murray6, H. Williams7, M. Talboys8, K. Kenny3, M. Holubinka4 1

Medical Physics, University of Malta, Msida, Malta Institute of Nuclear Medicine, University College London, London, UK 3 Nuclear Medicine Department, Oxford University Hospitals NHS Trust, Oxford, UK 4 Medical Physics Department, Portsmouth Hospitals NHS Trust, Portsmouth, UK 5 Radiological Sciences Unit, Imperial College Healthcare NHS Trust, London, UK 6 Institute of Cancer Research, Royal Marsden Hospital, London, UK 7 Nuclear Medicine Centre, Central Manchester University Hospitals, Manchester, UK 8 Medical Physics Department, Cardiff and Vale UHB, Cardiff, UK 2

The utilization of TOF improves image quality in PET by reducing noise propagation during image reconstruction process. The reduction in noise depends on the extent and distribution of the activity and the time resolution of the PET scanner. Large number of studies have looked at the benefits of TOF in oncological applications, there is limited published work on the benefits of incorporating TOF in cardiology, specifically quantification of a cardiac defect. Our aim was to objectively quantify the improvements gained using TOF in contrast/noise trade-off for cardiac defects compared to alternative reconstruction algorithms, including Point Spread Function (PSF) resolution recovery. The study was performed on three TOF PET/CT scanners; Siemens, Philips and GE. A cardiac insert (Data Spectrum, Model ECT/CAR/I) with a cold defect covering 11.8% of the myocardium was inserted into a 38 by 26cm anthropomorphic torso phantom (Data Spectrum, Model ECT/TOR/P). Six acquisitions were made to generate independent and decay corrected noise realizations. The experiment was designed to allow the study of the different reconstruction methods and different parameters within the reconstruction. The reconstructed images were analysed to measure the size of the cold defect and the contrast between the heart and the defect using a mask generated by segmentation of the corresponding CT images. TOF reconstruction outperformed non-TOF reconstructions in terms of contrast/noise trade-off. The results suggest that TOF acts as a signal boost, improves contrast/noise trade-off of cardiac defects and consequently provides a better clinical management of patients with cardiac ischemia/infarct.

***************** M16 (59)******************************* M16 Emission Tomography Instrumentation 2 / Front End and Data Acquisition Electronics 607

Friday, Nov. 1 10:30-12:30 Hall B2 Session Chair: Simon Cherry, University of California-Davis, United States; Heejong Kim, University of Chicago, United States

M16-1, A Flexible Geometry High Sensitivity SPECT Scanner for Molecular Imaging K. L. Walker, J. Zhou, J. Qi, S. R. Cherry, G. S. Mitchell Biomedical Engineering, UC Davis, Davis, CA, USA

We have built a very high sensitivity single-photon emission computed tomography (SPECT) scanner for molecular imaging. The system uses two collimator-less detector heads in close proximity to the imaging subject. Images are formed based on the compact geometry and solid angle effects alone. A variety of thin subjects (animals, plants, and well plates) have been imaged with a selection of isotopes: 99mTc (140 keV), 123I (159 keV), and 111In (172 and 247 keV). A maximum a posteriori (MAP) reconstruction method has been developed using Monte Carlo simulations; experimental results show the feasibility and validity of the proposed MAP method. Using GATE simulation, the sensitivity of our scanner with 3 mm thick NaI(Tl) detectors is: 46% for 99mTc, 44% for 123I, and 42% for 111In; our experimental sensitivity results are consistent with those from GATE simulation. Using pairs of capillary tubes, the spatial resolution was measured to be as good as 7 mm. Wells in a 96-well plate were imaged with activities less than 1 μCi each; the response of the system is linear and the amount of activity in each well can be quantified at the level of 2%. A high sensitivity system with spatial resolution on the order of a centimeter is useful for many molecular imaging applications which do not require good spatial resolution: for example, screening applications for drug development or novel imaging probes (small animals), material transport and sequestration studies for phytoremediation (plants), or for quantitative measurements of radiolabeled cells in vitro (well plates). M16-2, High-Resolution Brain SPECT Imaging Using Parallel and Tilted Detector Heads A. Suzuki, W. Takeuchi, T. Ishitsu, Y. Ueno, Y. Morimoto, K. Kobashi Central Research Laboratory, Hitachi, Ltd., Hitachi-shi, Ibarakiken, Japan

In a conventional brain SPECT system, surface of detector heads are parallel to the rotation z-axis, then the collimator surface is away from the brain surface at a position closer to upper slice of a cerebrum. So, we propose the new SPECT system in which detector heads were tilted to the z-axis so that the detector heads were closer to the brain. In addition, the parallel detector heads were also employed to obtain the complete projection data set. We evaluated the new SPECT system with the parallel and tilted detector heads by simulation. In the simulation study, the new SPECT system employed two parallel detector heads and two tilted detector heads. The tilted angle of the detector heads to the z-axis was 45 degree. The distance from collimator surface of the parallel detector heads to the z-axis was 130mm. The distance from the axial center point at collimator surface of the tilted detector head to the center point in the z-axis was 110mm. Planar spatial resolution at the z-axis was evaluated by the modulation transfer function (MTF). A cold rod brain 608

shaped phantom and cerebral blood flow phantom were evaluated. The projection data were generated by forward-projection of the phantom images using physics models and then Poisson noise at clinical level was applied to the projection data. The OSEM with physics models was used. We also evaluated a conventional SPECT system using four parallel detector heads. The planar spatial resolution of the tilted detector head at the z axis (z ≧ -30mm) was higher than that of the parallel detector head. The cold rod brain shaped phantom image showed that the conventional SPECT system could visualize up to 8mm-diameter rods. By contrast, the new SPECT system could visualize up to 6mm-diameter rods at upper slice of a cerebrum. The cerebral blood flow phantom image showed that the new SPECT system provided the higher resolution at thalamus as well as longitudinal fissure of cerebrum compared to the conventional SPECT system. M16-3, Introduction of a Novel Ultra-High Sensitivity Collimator for Brain SPECT Imaging M.-A. Park1, S. C. Moore1, R. Keijzers2, M. Keijzers2, M. F. Kijewski1 1 2

Radiology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA Nuclear Fields USA, Corp., Des Plaines, IL, USA

Noise levels of brain SPECT images are highest in central regions, due to preferential attenuation of photons emitted from deep structures. To address this problem, we designed and manufactured a hybrid collimator with ultra-short cone-beam focusing in the central regions and slant-hole collimation in the periphery (USCB). We evaluated this collimator for quantitative brain imaging tasks, and compared it to standard low-energy high-resolution (LEHR) and 39-cm-focal-length fan-beam (FAN) collimation. Very high count projection data of a five-compartment brain phantom were acquired with the three collimators on a dual-head SPECT/CT system. Separate acquisitions of each compartment, obtained by filling only one compartment with activity and the others with water, consisted of 60 angular views over a 360-degree circular orbit with 90 sec/view. All acquisitions were scaled for unit activity concentration. We reconstructed a projection dataset formed by summing datasets for the 4 striatal compartments. We also calculated the Cramer-Rao bounds on the precision of estimates of striatal and background activity concentration. In order to assess the potential of the new collimation system to detect changes in striatal activity due to use disease progression or response to therapy, we evaluated the precision of measuring a 5% decrease in right putamen activity. For the left caudate, located near the center of the brain, the detected counts were 9.8 (8.3) times higher for UCSB compared with LEHR (FAN), averaged over 60 views. The SNR of detecting 5% decrease putamen uptake was 8.5 for USCB and 3.7 for LEHR. The reconstructed striatal images using the USCB collimator alone agreed well with those of the other collimators. We have demonstrated the potential of USCB collimation for improved precision in estimating striatal uptake. The novel collimator may be useful for early detection of Parkinsons disease, and for monitoring therapy response and disease progression. M16-4, Optimizing Collimator Resolution/Sensitivity in SPECT Iterative Reconstruction J. Strologas1, S. Metzler2, X. Zheng2, W. Chang1 1 2

Department of Radiology and Nuclear Medicine, Rush University Medical Center, Chicago, IL, USA Department of Radiology, University of Pennsylvania, Philadelphia, PA, USA

The choice of collimator is the single most critical decision affecting the quality of reconstructed 609

images, the imaging time, and patient radiation dose in SPECT. If the collimator holes are narrow, fewer photons are detected, but each carries more information leading, to improved imaging resolution and worse noise due to Poisson statistics. On the other hand, wide holes lead to reduced noise and fewer artifacts at the expense of limited imaging resolution. This collimator resolution/sensitivity trade-off problem in SPECT system design demonstrates additional characteristics when iterative reconstruction with resolution recovery is utilized. In this paper we investigate the quality of reconstructed image of parallel-hole collimators of different geometric efficiencies, using Monte Carlo simulations and iterative reconstruction. To fairly compare the systems, we use the optimal number of iterations depending on the system, location and size of regions of interest, background levels and acquired number of counts. Although the final answer depends on all the above parameters, our goal is to study if it is generally possible to reconstruct images of similar quality at faster acquisition (or reduced radiation dose) by increasing the collimator sensitivity and recovering the resolution with iterative reconstruction. M16-5, Performance Evaluation of High-Resolution Parallel-Hole Collimator Materials at Sensitivity Equivalence Y.-J. Lee, D.-H. Kim, H.-J. Kim Department of Radiological Science and Research Institute of Health Science, Yonsei University, Wonju, Gangwon, Korea

In pixelated semiconductor SPECT system, spatial resolution can be improved by using a pixelated parallel-hole collimator with equal hole and pixel sizes. High absorption and stopping pixelated parallel-hole collimator materials are often chosen because of their good spatial resolution. Capturing more gamma ray however results in decreased sensitivity if the collimator geometric designs remain the same. Therefore, trade-off between spatial resolution and sensitivity is very important factor in SPECT imaging. The purpose of this study was to compare the spatial resolution with a pixelated semiconductor SPECT system using lead, tungsten, gold, and depleted uranium pixelated parallel-hole collimators at equal sensitivity. In this study, we performed a simulation study of the PID 350 (Ajat Oy Ltd., Finland) CdTe pixelated semiconductor detector, which consists of small pixels (0.35 0.35 mm2), using a Geant4 Application for Tomographic Emission (GATE) simulation. Spatial resolutions were measured at sensitivity equivalence with different collimator materials. Additionally, hot-rod phantom images were acquired for each source-to-collimator distance using GATE simulation. According to the results, at sensitivity equivalence, measured averages of the FWHM using lead, tungsten, and gold were 4.32, 2.93, and 2.23% higher than that of depleted uranium, respectively. Also, for FWTM, measured averages using lead, tungsten, and gold were 6.29, 4.10, and 2.65% higher than that of depleted uranium, respectively. Although, spatial resolution showed little difference among the different collimator materials, lead has better value regardless of the specific sensitivity or source-to-collimator distance. Our results demonstrated that lead and tungsten may be beneficial for not only significant cost reductions in collimator manufacturing but also avoiding impractical and rare materials. M16-6, A Dual-Head Multi-Pinhole Collimator Design for Stationary Clinical Myocardial Perfusion SPECT Imaging P. Yan1, G. S. P. Mok1, C.-H. Si1, B. M. W. Tsui2

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1

Department of Electrical and Computer Engineering, Faculty of Science and Technology, University of Macau, Macau, China 2 Division of Medical Imaging Physics, Department of Radiology, Johns Hopkins University, Baltimore, MD 21287, USA

Previously we had designed a dual-purpose multi-pinhole (MPH) collimator for a standard gamma camera for improved clinical myocardial perfusion (MP) SPECT with additional capability of small animal imaging. However, the standard SPECT system consists of two gamma cameras connected at ~90⁰ or L-mode. This study aimed to design an optimized MPH collimator for stationary MP SPECT imaging using a dual-head SPECT system arranged in L-mode. Two stationary L-mode configurations, L-mode-I/II, were proposed where the long axis of the left ventricle was perpendicular to either camera or in between. With the pre-defined pinhole pattern having minimal projection truncation and 25% for all regions in phantom and rat brain studies, but can be corrected to < 1% in rat brains via segmentation-based MRAC. M18-25, Performance Evaluation of Interpolated Average CT for PET Attenuation Correction in Different Lesion Characteristics C. Ho1, T. Sun1, T. H. Wu2, G. Mok1 1 2

Department of Electrical and Computer Engineering, University of Macau, Macau, China Department of Biomedical Imaging and Radiological Sciences, National Yang Ming University, Taipei, Taiwan

Previously we demonstrated the effectiveness of the interpolated average CT (IACT) for attenuation correction (AC) in PET in simulations and clinical patients. This study aims to evaluate the performance of IACT for thoracic lesions with different sizes, uptake ratios and locations. The XCAT phantom was used to simulate noisy F-18-FDG distribution based on the clinical count level with respiratory motion amplitude of 2 cm. The average activity and 671

attenuation maps represented static PET and cine average (CACT) respectively. IACT was generated by the end-inspiration and end-expiration phases of the attenuation maps (HCT-1 and HCT-8) using deformable registration method. Spherical 10 mm and 20 mm lesions were simulated at 4 locations individually, including the lower left lung (LLL), lower right lung (LRL), middle right lung (MRL) and upper right lung (URL). Two target-to-background ratios (TBR) of 4:1 and 8:1 were modeled. The noisy sinograms with attenuation modeling were generated and reconstructed with different AC maps by STIR (Software for Tomographic Image Reconstruction), using OS-EM with up to 300 updates. Normalized mean square error (NMSE), mutual information (MI) and TBR were analyzed. The NMSE and MI results showed that PETCACT and PETIACT were more similar to the original phantom as compared to PETHCTs. For TBRs, the differences between CACT/IACT and HCTs AC were more significant for lesions in the lower lung with PETHCT-8 showed higher TBR and PETHCT-1 showed lower TBR as compared to PETCACT/PETIACT for all lesion sizes and uptake ratios. The TBR for the LLL-20 mm lesion in PETHCT-8 was over estimated for ~156% for TBR=4:1. The TBRs for 10 mm lesion were more difficult to be recovered in all AC schemes. Better lesion localization and more stable quantitation for different lesion characteristics make IACT a good alternate for AC as compared to conventional HCT/CACT. M18-26, Calculated Attenuation Correction for Awake Small Animal Brain PET Studies G. I. Angelis1, M. Bickell2, A. Z. Kyme1, W. J. Ryder1, L. Zhou2, J. Nuyts2, S. R. Meikle1, R. R. Fulton1 1 2

Brain & Mind Research Institute, Faculty of Health Sciences, The University of Sydney, Sydney, Australia Nuclear Medicine and Medical Imaging Research Center, KU Leuven, Leuven, Belgium

Attenuation correction of small animal PET data is very important when quantitative images are of interest. Attenuation correction coefficients are conventionally obtained via a transmission or a computed tomography scan, which require anaesthetisation of the animal. However, in the context of awake and/or freely moving animals, where animal motion is compensated via appropriate motion tracking and correction techniques, anaesthetisation is no longer required. In this work we investigate the accuracy of a transmissionless attenuation correction approach based on the segmentation of the motion corrected emission image. Results on both phantom and real rat data acquired on the microPET Focus220 scanner, indicate good agreement between the segmentation based and conventional transmission based approach (~2% difference). In addition, the segmentation based approach has the potential to eliminate noise propagation from the measured transmission data to the reconstructed attenuation corrected emission images. M18-27, Scatter and Attenuation Corrections for a PEM Detector Using List-Mode OSEM C. S. Ferreira1,2, L. Cao3, R. Bugalho2, N. Matela1, C. Ortigao2, J. Varela2,4, P. Almeida1 1

FCUL/IBEB, Lisbon, Portugal LIP, Lisbon, Portugal 3 Division Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany 4 CERN, Geneva, Switzerland 2

The ClearPEM detector is a dual-head positron emission mammography system, specially designed for dedicated breast imaging. In addition to the rotational capability of the detector heads and the 3D acquisition, this scanner allows depth-of-interaction measurements on its LYSO:Ce 672

crystals. The total number of possible lines-of-response is, therefore, considerably large and due to the low statistics nature of PEM acquisitions, a List-Mode reconstruction algorithm is used, providing time-efficiency and accuracy. In PEM, data correction is essential for proper image quantification. Unlike current whole-body PET-CT scanners, the ClearPEM does not incorporate a simultaneous transmission image scan. An attenuation correction based on image segmentation was developed instead. The use of the emission image to obtain a model of the object contour was also the basis for a dedicated Monte-Carlo scatter correction. We present the application of these correction methods to a List-Mode OSEM reconstruction and we compare multiple methods to integrate the correction data into the reconstruction. Random events correction implementation and results were already previously reported. The attenuation and scatter correction tools implemented were validated using phantoms. Results for clinical cases are presented. Reconstructed images show a clear decrease of the attenuation effect, provided by the recovery of counts in the center of the object and also globally. Scattered events removal improved images allowing a clearer objects' contour delineation and facilitating lesions detection. In general, phantoms' uniform activity distribution was recovered and blurring effects were considerably reduced. The implemented methods proved to efficiently achieve their objective. An overall image improvement was obtained. An extended analysis will be presented at the conference including quantification with non-uniform phantoms. M18-28, GPU-Accelerated Monte Carlo Based Scatter Correction in Brain PET/MR M. E. Gaens1, J. Bert2, U. Pietrzyk1,3, N. J. Shah1, D. Visvikis2 1

Institute of Neuroscience and Medicine - 4, Forschungszentrum Juelich, Juelich, Germany INSERM UMR1101, LaTIM, CHRU Brest, France 3 Department of Mathematics and Natural Sciences, University of Wuppertal, Wuppertal, Germany 2

A main advantage of PET is that it can provide truly quantitative results. In order to achieve this goal an accurate scatter correction is essential. Despite some drawbacks, the currently used single scatter simulation approach is clinically applicable, whereas Monte Carlo (MC) simulations have been shown to provide accurate results, but are still too slow to be used routinely. In this work, the high computing capabilities of graphical processing units (GPUs) are exploited to accelerate PET MC simulations in order to facilitate their use in clinical practice. Starting from voxelized images, the annihilation photons are tracked through to their detection in the simulated PET scanner geometry, while retaining the information on their associated scattering interactions. The scatter distribution provided by the simulation can subsequently be used to correct the measured datasets. The new GPU implementation was validated by comparison with GATE simulation results and found to provide equivalent accuracy. The acceleration factor on the GPU compared to current GATE simulations was 85 for a voxelized brain phantom study. The speedup of MC simulations provided by the graphics processors represents a major step towards a clinically feasible and physically accurate scatter correction. M18-29, A Comparison of Scatter Correction Methods for Quantitative Lu-177 SPECT R. de Nijs1, V. Lagerburg2,3, T. L. Klausen1, S. Holm1 1

Dept. of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark

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Dept. of Clinical Physics, Spaarne Hospital, Hoofddorp, the Netherlands Dept. of Medical Physics, Catharina Hospital, Eindhoven, the Netherlands

Patient specific dosimetry of Lu-177-DOTATATE treatment of neuroendocrine tumors is important, because uptake differs across patients. SPECT based dosimetry requires a conversion factor between the acquired number of counts and the activity, which depends on the applied scatter correction techniques and collimators. In this experimental study energy window subtraction based scatter correction methods are compared quantitatively. Lu-177-SPECT images of a phantom with known activity concentration ratio between filled differently sized hollow spheres and uniform background were acquired for three different types of collimators (Low Energy High Resolution (LEHR), Low Energy General Purpose (LEGP) and Medium Energy General Purpose (MEGP)). Counts were collected in several energy windows and scatter correction was performed by applying different methods, viz. Effective Scatter Source Estimation (ESSE), Triple and Dual Energy Window (TEW and DEW), Double Peak Window (DPW), downscatter correction and no scatter corrections. The intensity ratio between the spheres and the background was measured and corrected for the partial volume effect and used to compare the performance of the methods. Low energy collimators with 208 keV energy windows give rise to artifacts. For the 113 keV energy windows large differences in the ratios for the spheres were observed. In the case of MEGP collimators with the ESSE correction technique the measured ratio is close to the real ratio for both energy windows, and the differences between the spheres are limited. For quantitative 177Lu imaging the MEGP collimators are advised. Both energy windows can be utilized, if the ESSE correction technique is applied. The difference between the calculated and the real ratio is less than 10% for both energy windows. For spheres with a diameter down to approximately 25 mm (8 mL) one conversion factor can be used, which makes accurate dosimetry possible for lesions of at least this size. M18-30, Energy Based Scatter Correction Method for a Solid-State SPECT Scanner W. Takeuchi1, Y. Morimoto1, A. Suzuki1, Y. Ueno1, K. Kobashi1, N. Kubo2, T. Shiga3, N. Tamaki3 1

Central research lab., Hitachi Ltd., Tokyo, Japan Central Institute of Isotope Science, Hokkaido University, Sapporo, Japan 3 Graduate School of Medicine, Hokkaido University, Sapporo, Japan 2

Objectives: Energy resolution of solid-state detector such as CZT or CdTe is good enough to separate photopeaks of Tc-99m (141keV) and I-123 (159keV), however, down-scatter is unavoidable error in simultaneous dual-isotope imaging. In addition, caused by inner-crystal scatter or k-escape, considerable fraction of primary events is measured as lower energy events. To improve the accuracy of dual-isotope imaging, a modified triple-energy window (TEW) method was developed. Methods: For dual-isotope imaging, five energy windows (Tc-lower, Tcmain, shared sub-window of Tc-upper and I-lower, I-main, and I-upper) are used. In the modified TEW method, response for primary events (RPE), obtained from pre-measurement of scatter-free radiation sources, is used to estimate primary fractions of main and sub-windows. To avoid overcorrection, the counts caused by primary events in sub-windows are estimated using RPE and then subtracted from the counts of sub-windows. The count of scattered events in I-main is corrected by the modified TEW using I-lower, I-main, and I-upper windows. Then, contaminations from I-123 in Tc-related windows, are compensated using scatter corrected I-main counts and RPE for I-123. Finally, count of scattered events in Tc-main is corrected by the modified TEW using Tc-lower, Tc-main, and Tc-upper windows. To evaluate the accuracy of the correction method, two phantom 674

experiments were conducted with our prototype CdTe SPECT. Results: The determination coefficients between the activity and pixel value were 0.997 for Tc-99m and 0.998 for I-123 in image of a phantom which had five various mixtures of Tc-99m and I-123 and a cold segments. In another cylindrical phantom image, pixel value ratio of single isotope Tc-99m (111MBq) image to mixture of Tc-99m (111MBq) and I-123 (75MBq) image was 0.99 in Tc-99m window. Conclusions: By using the developed correction method with solid-state detector SPECT, quantitatively accurate dual-isotope imaging can be realized. M18-31, A Spectral Forward Model for Single Scatter in PET I. G. Kazantsev Image Processing Department, Institute of Computational Mathematics and Mathematical Geophysics, Novosibirsk, Russia

In this extended abstract an analytical aspects of deriving an idealized forward model of single scatter in positron emission tomography (PET) are discussed. The forward model is derived based on the analytical simulation model known as Single Scatter Simulation (SSS) approximation. The spectral forward model is developed as a limit case of the SSS approximation applied to a PET system of two detectors $(A, B)$ where detector $A$ counts unscattered and $B$ registers the single scattered photons (with certain scatter angle $\theta$) from the same annihilation event, provided a certain geometrical constraints. It is shown that single scatter image formation includes integration of emitter activity $f$ over bundle of compounded cones with common vertex at point $A$. Those cone integrals are weighted by linear attenuation $\mu$ and some geometric factors. It is shown that under assumption on $\mu=const,$ a reconstruction technique known as the defocus-gradient backprojection can be applied for inversion of the derived single scatter forward transform. M18-32, PET/MR Imaging of the Head/neck: Automatic Correction of Dental Implant Artifacts Exceeding Anatomical Surfaces C. N. Ladefoged1, F. L. Andersen1, T. Beyer2, A. E. Hansen1, S. H. Keller1, I. Law1, L. Hoejgaard1, A. Kjaer1, F. Lauze3 1

Dept. of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, Copenhagen, Denmark Center for Medical Physics and Biomedical Engineering, University of Vienna, Vienna, Austria 3 Dept. of Computer Science, University of Copenhagen, Copenhagen, Denmark 2

In combined PET/MR, attenuation correction (AC) is performed indirectly based on the available MR image information. Metal implant-induced susceptibility artifacts and subsequent signal voids that exceed the actual implant volume, challenge MR-based AC (MR-AC). We evaluate the accuracy of MR-AC in PET/MR in patients with metallic dental work, and propose a clinically feasible correction method of the metal-induced signal voids that exceed the surface boundaries of the patient anatomy. The resulting bias in AC-PET is severe in regions in and near the signal voids, areas that can have severe implications for head and neck cancer. Notably, the bias is present also in areas further away from the implants. In selected cases this bias may markedly affect regions used commonly as reference for kinetic modeling. The method proposed successfully corrects the artifacts extending to the boundary of the volume by filling them with soft tissue. 675

M18-33, A Post-Processing Method for Improving Contrast and Reducing Cupping Artifacts in Low-Energy CBCT Images C. Thanasupsombat1, P. Pengvanich1, S. Aootaphao2, S. S. Thongvigitmanee2 1 2

Dept. of Nuclear Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok, Thailand Image Technology Laboratory, National Electronics and Computer Technology Center, Pathumthani, Thailand

X-ray scattering in the cone beam computed tomography system can lead to undesirable reduction in contrast and overall image quality of reconstructed images. The scatters inside the object cause a serious problem, especially when the object is large and contains a lot of materials, such as bones and soft tissues. In this work, the amount of X-ray scattering is numerically estimated using the Monte Carlo method based on the GEANT4 software. A new procedure that employs the numerical result to improve the contrast and the overall quality of the actual reconstructed images produced by a prototype dental CBCT system is introduced. The procedure has been primarily tested on various simple geometry CT objects, and found to be able to improve the contrast and the cupping artifacts of the projection images. Further analysis also shows that the calculated CT numbers of the materials derived from the corrected image are more in line with the documented values than those from the uncorrected one. M18-34, Impact of detector moving on gamma camera dead-time in high dose radioimmunotherapy (RIT) using 131I whole-body planar imaging Y. S. Lee1,2, K. M. Kim1, J. G. Kim1, J. S. Kim1, W. Lee1, H.-J. Kim2, B. I. Kim1, S. M. Lim1 1 2

Molecular Imaging Research Center, Korea Institute of Radiological and Medical Sciences, Seoul, rep. of korea Department of Radiological Science, Yonsei University, Wonju, rep. of korea

It is well known that high activity of I-131 induces the significant decrease of detected count, due to dead-time effect. Whole-body (WB) planar imaging using moving detector has been used widely in RIT protocol for the estimation of WB dose as well as organ and tumor dose. Despite of many studies for dead-time effect in I-131 static imaging up to now, there has been no study considering the effect of moving detector on high count rate. In this work, we investigate the effect of dead-time in WB I-131 imaging for high-dose radioimmunotherapy (RIT). A clinical SPECT/CT (SYMBIA T2, Siemens) with high energy collimator has been used. I-131 activity was decreased from 5550 ~ 9.25 MBq in 14 steps. Energy window was set to 364 keV 20%. I-131 source was well-shielded by a lead cylinder and placed at the center of detector. Wide horizontal range of planar image covering WB length was also obtained with the same I-131 by moving detector through horizontal distance (180 cm, 15cm/min). For every steps of measurement, the both static and WB planar images were obtained with the detector-to-source distances of 5 cm and 25 cm, respectively. On the planar images, the detector size of ROI was drawn to get the total count. Dead-time of WB images by moving detector were smaller (17.5% for both 5 cm and 25 cm) than those of static images, which resulted in less underestimated counts in WB images. In neighbored area close to hot radioactivity, there was a little effect of dead-time due to radiation penetrating collimator septa. Movement of detector contribution was to reduce the dead-time effect. Therefore, when designing high-dose RIT study using the protocol of static and WB imaging, the both dead-time correction factors for static and moving detector should be determined for appropriate dosimetry and correction factor can be determined regardless of the source distribution. 676

M18-35, Development of a Method Calculating Detection Efficiency Maps for Quantitative Image Reconstruction of a Compton Camera Y. Nagao1, M. Yamaguchi1, N. Kawachi2, S. Fujimaki2, T. Kamiya1, S. Takeda3, S. Watanabe3, T. Takahashi3, K. Torikai4, K. Arakawa1,4, T. Nakano4 1

Takasaki Advanced Radiation Research Institute, Japan Atomic Energy Agency, Takasaki, Japan Quantum Beam Science Directorate, Japan Atomic Energy Agency, Takasaki, Japan 3 Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Japan 4 Heavy Ion Medical Center, Gunma University, Maebashi, Japan 2

We have been studying the application of Compton cameras to the field of medicine and biology. In order to analyze quantitatively the physiological functions of the target subjects, it is essential to estimate the quantitative distribution of radioactive tracers within a given field of view (FOV) of the camera, therefore a quantitative image reconstruction method for Compton cameras has been investigated. In a statistical image reconstruction algorithm such as ML-EM (maximum-likelihood expectation-maximization), detection efficiency maps play an important role in quantitative image reconstruction. Particularly, the spatial variations of efficiency are large in the near-field area of the camera, which is the main FOV in the medical and biological application. We have developed a method to calculate the efficiency maps considering geometrical and physical conditions such as solid angles, configuration of the detectors, interaction cross sections, etc. In order to test the validity of the method, a Monte Carlo simulation was carried out. The point sources of 511 keV photons were placed in a plane at a distance of 150 mm from the scattering detector of the CdTe semiconductor Compton camera. The efficiency map agreed well with the result of Monte Carlo simulation. Using the efficiency map, an imaging experiment of a 22Na (511 keV) source in the shape of line was performed. The source was placed in the same plane as considered in Monte Carlo simulation. The shape of line is well reconstructed by list-mode ML-EM, though distribution of activity is not uniform sufficiently. Non-uniformity of radioactivity in the line image is considered to be due to noise events that are incorrectly reconstructed. M18-36, Techniques for Improving the Energy and Timing Performance of a Light-Sharing PET Detector at High Count-Rates S. Krishnamoorthy1, J. Panetta1, B. Legeyt1, R. I. Wiener1, S. Surti1, J. S. Karp1,2 1 2

Radiology, University of Pennsylvania, Philadelphia, PA, USA Physics and Astronomy, University of Pennsylvania, Philadelphia, PA, USA

The continuous improvements in the sensitivity, performance of modern-day PET scanners has resulted in significantly reduced scan-times. This improvement though has placed significant demand of the count-rate performance of the detector and its readout electronics. The count-rate performance is particularly of concern in a light-sharing detector as in addition to temporal pileup there could also be spatial pileup. While efforts have been made to improve count-rate performance in a light-sharing detector, the focus thus far has primarily been on preserving the energy and spatial degradation by correcting for post-pulse pileup. With time-of-flight gaining routine acceptance in the clinic it is equally important that attention be paid to preserve the timing resolution at high-count rates. This paper focuses on developing techniques to preserve both, the energy and timing information in a light-sharing detector operating at high count-rates. This task is facilitated by the availability of high-speed (GSamples/s) digitizers. While it offers an elegant 677

solution, it is equally important that the design be optimized to enable both performance and throughput. Hence we use a combination of analog shaping and pulse processing. Analog shaping has been realized for a LaBr3 based detector, and via bench-top experiments and simulations we show initial feasibility of our technique. Further experimental evaluation with a large-area detector, optimization and investigation of the technique for practical implementation on a scanner would be presented. M18-37, Determination of Dense Motion Fields for the Whole Torso Surface Using Two Microsoft Kinects M. Hess, F. Gigengack, F. Buether, M. Dawood, K. P. Schaefers European Institute for Molecular Imaging, Muenster, Germany

Breathing motion combined with elongated scanning times in positron emission tomography (PET and SPECT) leads to unwanted blurring artifacts in reconstructed images. Respiratory gating is commonly used for compensating these effects in applications like radiotherapy treatment and diagnostical imaging. Various approaches were already proposed for capturing the necessary respiratory signal: The external motion of the patients body surface can be exploited as a surrogate of the internal motion. Systems like the widespread Real-time Position Management (RPM, Varian Medical Systems, Palo Alto, CA) and previously proposed methods using the Microsoft Kinect only provide one-dimensional signals for a single region (marker). However, the motion in a single region on the surface might not be sufficient to distinguish between breathing phases in which the position of organs and lesions can be varied (e.g. hysteretic effects). Other systems that take multiple regions into account often use expensive time-of-flight (ToF) cameras and/or markers that possibly lead to inconvenience. The aim of this work is to present a low-cost method for precisely depicting a global motion field for the whole torso by using two Microsoft Kinects. Thus, it is possible to calculate an individual motion signal for each point on the surface. For validation purposes the method was tested in experimental settings. M18-38, Study of an Inertial Measurement Unit for Real Time Motion Tracking in Medical Imaging K. Ziemons1, M. Titze1, S. Beging1, R. Fulton2 1 2

Medical Engineering a. Technomathematics, FH Aachen University of Applied Sciences, Aachen, Germany Department of Medical Physics, The University of Sydney, Sydney, Australia

Given the resolution of current medical imaging systems, accurate and reliable motion correction requires a motion tracking system to improve image data quality. Even in the latest tomographic devices there are crucial image errors to be found so that a simple and preferably cost-efficient method of motion tracking is needed. Therefore the performance of a MicroElectroMechanicalSystems (MEMS) is evaluated for use in a correction system, because advantages, such as fast update times, small package sizes and cheap prizes are given. The inertial microsensor module SD746 with a three-axis micro-machined gyroscope and three-axis micromachined accelerometer produced by SensorDynamics was chosen for this initial evaluation study. Mounted on an ACE Evaluation Board it allows a quick access to the measurement data through digital interfaces. The communication between sensor module and computer was realized using NI 678

LabView. Data acquisition and further real time calculations were implemented and several test were performed, mainly concentrating on rotational movements. Offset correction of the gyroscope rate data reduced the drift in calculated angle about several hundred degrees. Furthermore show rotational results a deviation of 1.53 for a 100s measurement, which is mainly caused by bias drift, noise and the accumulation of errors using numerical integration. Since high precision is necessary in imaging correction systems, a simple complementary filter was tested to further increase the accuracy, but results show that quadrant dependencies occur and more complex filter algorithms, such as Kalman filter, are inevitable. Most commonly Kalman filter implementations for InertialMeasurementUnits (IMU) can be found in context of vehicle position tracking. In addition to Kalman filter the fusion of several MEMS is also a common approach. The algorithm then uses control vectors provided by other inertial measurement units different to the one that has to be evaluated. M18-39, Multiple Target Marker Tracking for Real-Time, Accurate, and Robust Rigid Body Motion Tracking of the Head for Brain PET P. J. Noonan1, J. M. Anton-Rodriguez1, T. F. Cootes2, W. A. Hallett1, R. Hinz1 1 2

University of Manchester, Manchester, UK Imanova Centre for Imaging Sciences, Hammersmith, London, UK

Although motion correction in medical imaging is well established and has attracted much interest and research funding, a gap still exists in that there is a lack of reliable, low-cost hardware to enable such techniques to be widely adopted in healthcare. For PET, motion during scanning causes image blur which degrades image quality and quantifiability. In most marker based motion tracking systems used for brain imaging, a single tracking tool is fixed to the subject, however it is crucially important to ensure that the tool is rigidly fixed to the subject's head otherwise the tool may slip and the tracking data becomes unreliable. A tracking system has been developed using open source code and a single low cost digital camera that tracks multiple, 5 mm^2 target markers printed onto adhesive paper which are attached to the subject's forehead. The system can track the 6 degree of freedom motion of the head to sub mm precision and in real-time while being robust against facial deformations that may move the target markers non-rigidly. In this proof of principle study a standard, consumer grade, visible light webcam was used with a resolution of 640x480 pixels that corresponded to an active target tracking area of ~80x60 mm, operated at 30 Hz, and achieved simultaneous sub-mm tracking of multiple markers. M18-40, Fast and Practical Head Tracking in Brain Imaging with Time-of-Flight Camera J. Wilm1,2, O. V. Olesen1,2,3, R. R. Jensen1, L. Hojgaard2, R. Larsen1 1

Department of Applied Mathematics and Computer Science, Technical University of Denmark, Kgs. Lyngby, Denmark 2 Department of Clinical Physiology, Nuclear Medicine & PET, Rigshospitalet, Copenhagen, Denmark 3 Athinoula. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts, USA

This paper investigates the potential use of Time-of-Flight cameras (TOF) for motion correction in medical brain scans. TOF cameras have previously been used for tracking purposes, but recent progress in TOF technology has made it relevant for high speed optical tracking in high resolution 679

medical scanners. Particularly in MRI and PET, the newest generation of TOF cameras could become a method of tracking small and large scale patient movement in a fast and user friendly way required in clinical environments. We present a novel methodology for fast tracking from TOF point clouds without the need of expensive triangulation and surface reconstruction. In order to reduce systematic bias, we calibrate for wiggling error and lens distortion. Our TOF tracking algorithm estimates the relative pose of the head by means of a modified, robust version of the iterative closest point (ICP) algorithm. Tracking experiments with a motion controlled head phantom were performed with a translational tracking error below 2 mm and a rotational tracking error below 0.5. M18-41, Analysis of 4DCT Patient Breathing Pattern Using Recurrence Plots S. H. Lee1,2, H. Kim1,2, S. C. Han1,2, M.-S. Kim1,2,3, H.-J. Yoo3, C.-Y. Yi4, S. Park1, H. Jung1,2, Y. H. Ji1,2,3, K. B. Kim1,2,3 1

Dept. of Radiological Cancer Medicine, University of Science & Technology, Daejeon, Korea Research Center for Radiotherapy, Korea Institute of Radiological and Medical Sciences, Seoul, Korea 3 Dept. of Radiation Oncology, Korea Cancer Center Hospital, Seoul, Korea 4 Center for Ionizing Radiation, Korea Research Institute of Standards and Science, Daejeon, Korea 2

INTRODUCTION We developed a simple tool to characterize and evaluate breathing pattern based on recurrence plot (RP) and recurrence quantification analysis (RQA). MATERIALS AND METHODS The study of recurrence is often used to understand the dynamics of nonlinear systems. A recurrence plot is a graph which represents those times at which the system recurs to a former state, at which a phase space trajectory visits the same area in the phase space. A graphical tool were developed by using Matlab graphic user interface (version R2012b, Mathworks) to import and evaluate breathing patterns with recurrence parameters, such as Recurrence rate (RR), Determinism (DET), Laminarity (LAM), Longest diagonal line(Lmax), Entropy (ENTR), and Trapping time (TT). The free breathing sine curves, breathing patterns obtained by breathing simulator and 9 patients of breathing pattern ,before/after contrast media (CM), which were gained by Varian Real-Time Position Management (RPM) system (Varian Medical Systems, Palo Alto, CA, USA) during 4DCT scan (Lightspeed RT 16, GE, Germany) were compared and analyzed. RESULTS AND DISCUSSION A recurrence plot and phase space plot from time-delay embedding technique showed distinguishable differences between regular and irregular breathing pattern as well as before/after CM. But the result of present study seems there are no specific relationships of patients breathing pattern between before and after CM during CT scan. The breathing signal severely depends on patient case. If one system could be the explicit standard of comparison, such as respiratory guided radiotherapy, it is thought that recurrence plot would be the powerful tool for comparison of two systems. CONCLUSION Recurrence quantification analysis is a powerful discriminatory tool which can provide objectivity regarding the degree of determinism characterizing the system, state changes, as well as degrees of complexity and/or randomness. M18-42, Extracting a Respiratory Signal from Raw Dynamic PET Data That Contain Tracer Kinetics P. J. Schleyer1, K. Thielemans1,2, P. K. Marsden1

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1 2

Division of Imaging Sciences & Biomedical Engineering, King's College London, London, UK Institute for Nuclear Medicine, University College London, London, UK

Data driven gating (DDG) methods provide an alternative to hardware based respiratory gating for PET imaging. Several existing DDG approaches obtain a respiratory signal by observing the change in PET-counts within specific regions of acquired PET data. Currently, these methods do not allow for tracer kinetics which can contribute to the respiratory signal and introduce error. In this work, we describe and evaluate a DDG method for dynamic PET studies that exhibit tracer kinetics. This was based on an existing approach that uses spectral analysis to locate regions within raw PET data that are subject to respiratory motion. In the new approach, overlapping short-time Fourier transforms were used to create a time-varying 4D map of motion affected regions. Additional processing was required to ensure that the relationship between the sign of the respiratory signal and the physical direction of movement remained consistent for each temporal segment of the 4D map. The change in PET-counts within the 4D map during the acquisition were then used to generate a respiratory curve. Using 26 min dynamic NH3 PET acquisitions which included a hardware derived respiratory measurement, we show that tracer kinetics can severely degrade the respiratory signal generated by the original DDG method. In some cases, the transition of tracer from the liver to the lungs caused the respiratory signal to invert. The new approach successfully compensated for tracer kinetics and improved the correlation between the data-driven and hardware based signals. On average, good correlation was maintained throughout the PET acquisitions. M18-43, Estimation of Decoding Error for Light Sharing Based PET Detector Module Using a Gaussian Mixture Model Q. Wei1,2, T. Ma1,2, S. Wang1,2, T. Dai1,2, Y. Jin1,2, Y. Liu1,2 1 2

Engineering Physics, Tsinghua University, Beijing, China Key Laboratory of Particle & Radiation Imaging, Ministry of Education, Beijing, China

Positron emission tomography (PET) is typically based on 2-D array of scintillation crystals and light sharing technique decoded by Anger-logic. The decoded result is a pseudo-position of the gamma interaction. A crystal position map generated from the flood histogram is used as a crystal look-up table (CLT) to assign each pseudo-position to a specific crystal. For the light sharing based PET detector module, the crystal responses overlap each other, which introduces position decoding error. In this paper, the position decoding error is quantitatively calculated by decoding error ratio (DER), which is defined as the probability of the events of one crystal assigned to others. The calculation method is based on the Gaussian mixture model (GMM) and CLT. Firstly, the flood histogram is estimated by GMM. A method based on the segmentation results of a neighborhood standard deviation (NSD) based algorithm is applied to estimate the initial parameter values. Three CLTs generated by manual segmentation, by GMM and by a NSD based algorithm were applied to calculate DERs, and the results showed that flood histogram segmented by GMM and NSD based algorithm achieved lower DERs, which is expected to get higher spatial resolution. The detector spatial resolution is affected by DERs, however it is not quantitatively studied in the earlier literatures. In the future work, we will improve the spatial resolution estimation function including the decoding error factor with a function of DERs and use simulation study to verify it.

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M18-44, Recovery of Multi-Interaction Photon Events to Improve the Performance of PET Scanners E. Lage1, V. Parot1, S. R. Dave1, J. M. Udias2, S. C. Moore3, A. Sitek4, M.-A. Park3, J. J. Vaquero5, J. L. Herraiz1 1

Madrid-MIT Consortium, Massachusetts Institute of Technology, Boston, MA, USA Grupo de Fisica Nuclear, Universidad Complutense de Madrid, Madrid, Spain 3 Dept. of Radiology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA 4 Dept. of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, Spain 5 Dept. Ingeniera Biomdica e Ingeniera Aeroespacial, Universidad Carlos III de Madrid, Leganes, Spain 2

Multi-interaction photon (MIP) coincidences are events coming from a positron-electron annihilation in which more than two γ-rays are detected simultaneously because at least one of the two original photons deposited its entire energy in more than one detector element. These coincidences are usually discarded in PET scanners as it is not possible to assign them to a unique line-of-response (LOR). Existing methods to recover MIP events are mainly based on Compton scatter kinematics. We propose a methodology which uses the measured double-coincidence distribution to sort MIP coincidences into LORs. The PET component of a preclinical PET/CT scanner (Argus/CT, Sedecal S.A., Spain) was adapted to enable the detection and acquisition of MIP coincidences. The effect of including MIP events recovered using several methods was studied in terms of image quality and noise equivalent count (NEC) rate following the guidelines described in the NEMA NU-4 protocol. Recovery of the MIP coincidences using the proposed methodology increased the peak NEC rates by 15.25% and 17.23% when imaging 18F for mouseand rat-sized objects respectively. Furthermore, this method is capable of simultaneously providing better SNR and contrast for hot lesions than those achieved using standard coincidences, while preserving recovery coefficients and contrast in cold lesions. Since the proposed approach can be easily implemented in block-detector and high-granularity detector-based scanners, this work provides a means to effectively increase the photon sensitivity of new or existing preclinical and clinical PET scanners M18-45, A Neighborhood Standard Deviation Based Algorithm for Generating PET Crystal Position Maps Q. Wei1, X. Li2, T. Ma1, S. Wang1, T. Dai1, P. Fan1, Y. Yu1, Y. Jin1, Y. Liu1 1 2

Engineering Physics, Tsinghua University, Beijing, China Division of Metrology in Ionizing Radiation and Medicine, National Institute of Metrology, Beijing, Chia

Positron emission tomography (PET) is typically based on 2-D array of scintillation crystals decoded by Anger-logic. The decoded result is a pseudo-position of the gamma interaction. A crystal position map (CPM) generated from the flood histogram is used as a look-up table to assign each pseudo-position to a specific crystal. The precision of CPMs crucially affects the detector spatial resolution. In this paper, we developed a new algorithm which is based on neighborhood standard deviation (NSD) for generating PET CPM. We first calculate the NSD of the flood histogram including standard deviation in x and y directions. NSD map has bright strips whose peaks correspond to the valley of the flood histogram excactly right. Compared to the flood histogram, NSD has better signal to noise ratio, more count consistency and higher correlation. The profiles of NSD are fitted to Gaussian mixture functions using nonlinear least-square method. By selecting a good quality profile as a starting point and using the primer profiles fitting results 682

as the initial values, the strip peaks can be extracted correctly. At last, the CPM can be conveniently generated by a scan line algorithm. The proposed algorithm was applied in Inliview 3000 PET/SPECT/CT system. 115 of 120 PET detector blocks can be automatically segmented. A hot rod phantom experiment was performed, and the reconstructed results show that the image with CPM generated by NSD based automatic method achieves higher spatial resolution than the one with CPM generated by manual segmentation. All in all, the proposed method is fast, robust and accurate. M18-46, Accelerate the Acquisition of Imaging Probes Using Spatiotemporal Processing M. Jin1, J. Yu1, W. Chen1, G. Hao2, X. Sun2 1 2

Dept. of Physics, University of Texas at Arlington, Arlington, TX, United States Dept. of Radiology, University of Texas Southwestern Medical Center, Dallas, TX, United States

A quick localization of the tumor site to guide the therapeutic administration is very important for an image guided cancer therapy to decrease both mortality and morbidity, especially in prolonged procedures, such as photodynamic and photothermal therapies. Consequently, the images have to be updated quickly enough to capture the patient motion and the movement of therapeutic device, which poses a significant challenge on functional imaging probes. Besides increasing the sensitivity of imaging detectors, advanced image processing methods may play an important role to overcome this challenge. In this work, we investigate the effectiveness of the spatiotemporal processing to shorten the acquisition time to be able to capture the object motion with a good quality image. The simulation study of beta imaging of a moving tumor phantom demonstrated that the spatiotemporal processing can yield a more accurate image than either a short acquisition with spatial smoothing or a prolonged acquisition. The receiver operating characteristic curve analysis also reveals a potential large benefit on the tumor tissue classification when further shortening the acquisition time. M18-47, Optimal Contrast as a Function of Noise for Butterworth Filtering of 111InPentetreotide SPECT When Using Model-Based Compensation A. Larsson1, D. Holmberg1, T. Sundstrom2, J. Axelsson1, K. Riklund2 1 2

Dept. of Radiation Sciences, Radiation Physics, Umea University, Umea, Sweden Dept. of Radiation Sciences, Diagnostic Radiology, Umea University, Umea, Sweden

It may be difficult to detect small tumors with 111In-pentetreotide SPECT, because of high noise levels and low spatial resolution. To detect tumors at an early stage is, however, important for efficient cancer treatment. The liver, which has a relatively high uptake of 111In-pentetreotide, is a common organ for somatostatin-positive metastases from neuroendocrine tumors, and this study is focused on contrast as a function of noise for small tumors in liver background. The study is a continuation of a previous study where collimator choice, number of projections and OSEM settings were analyzed. In this new study, post-filtering was optimized for 111In-pentetreotide SPECT with model-based OSEM reconstruction. We chose the Butterworth filter which due to its wide variability and contrast improving properties is commonly used. Monte Carlo simulations of a patient-like digital phantom with realistic 111In-pentetreotide uptake were performed, with added liver tumors (diameters 1.2 cm and 2.0 cm). Both extended low-energy general-purpose 683

(ELEGP) and medium-energy general-purpose (MEGP) collimators were evaluated, with 10 realistic noise realizations of each simulated image set. For Butterworth post-filtering, power factors (P) were varied from 4 to 12, in steps of 2, and critical frequencies (fc) were varied from 0.40 cm-1 to 1.0 cm-1, in steps of 0.10 cm-1. Reconstructed images without post-filtering were also included for comparison. The average tumor contrast as a function of noise was then calculated for a range of OSEM iterations. We found that ELEGP was the better collimator (as in previous studies), and that the optimal filter parameters depend on tumor size. For the same noise level, 1.2 cm tumors had the highest contrast for images that were not post-filtered, and this was true for both collimators. For the 2.0 cm tumors, the parameters fc=0.50 cm-1, P=12 were most optimal for both collimators. Some of the parameter settings gave, however, very similar results. M18-48, Investigation on Parameter Selection of Non-Local Means Filters Using CT Side Information for Multiple I-131 SPECT Scans S. Y. Chun1, Y. Dewaraja2 1 2

Ulsan National Institute of Science and Technology (UNIST), Ulsan, Republic of Korea University of Michigan, Ann Arbor, MI, USA

Non-local means (NLM) filtering methods using CT side information for I-131 SPECT estimation have a great potential for improving dose-response evaluations. However, it is challenging to determine optimal filter parameters of these filters. In SPECT-based dosimetry for I-131 radioimmunotherapy, several parameter optimization steps are necessary since several scans are obtained for different level of counts. In this paper, we propose a practical criteria for choosing filter parameters of NLM filters using CT side information without having the true image and investigate the relationship between quantification results and parameters empirically. We show that using usual criteria for parameter selection such as root mean square error may degrade the quantification accuracy of recovery coefficients and our suggested criteria can avoid this undesirable results. Our results show that the parameters and the count level do not have a linear relationship for high noise levels. XCAT simulation results show that the NLM filtering method with CT side information decreased the root mean square error and increased the recovery coefficients up to 39% and 7% as compared to no filtering, respectively, when we determine filtering parameters to minimize our proposed criteria. M18-49, Post-filtering of PET image based on noise characteristic and spatial sensitivity distribution J. H. Kim, I. J. Ahn, W. H. Nam, Y. Chang, J. B. Ra Department of Electrical Engineering, KAIST, Daejeon, Republic of Korea

Positron emission tomography (PET) images usually suffer from a noticeable amount of statistical noise. In order to reduce the noise, a post smoothing process is usually adopted in conventional PET systems. However, its performance is limited because the process is usually based on a Gaussian random noise which is quite distinct from the noise of PET images. It has been reported that mean values and noise variances of each voxel have a linear relationship in a PET image reconstructed by expectation-maximization (EM). In addition, we observe that the slope of linearity depends on the spatial sensitivity distribution in a PET system. Based on those properties, 684

we determine a unique slope of the mean-variance linearity for a given PET system. Meanwhile, a block matching 3D (or 4D) algorithm is known as the state of the art in Gaussian noise reduction. To effectively apply it for noise reduction of PET images, we first perform a noise characteristic conversion from PET image noise to Gaussian random noise using the pre-determined slope of linearity. We then apply a block matching 4D (BM4D) algorithm and reconvert the result. Using simulation phantoms, we demonstrate that proposed algorithm can effectively reduce the noise in the whole image region while minimizing image resolution degradation. M18-50, Sharpening and Denoising of Dynamic PET Images with Coupled Vector-Based Anisotropic Diffusion and Shock Filtering P. Gonzalez1,2, V. Jaouen1, S. Stute3, M. Mora2, D. Guilloteau1, I. Buvat4, C. Tauber1 1

UMRS INSERM U930 - Universite de Tours, Tours, France DCI Universidad Catolica del Maule, Talca, Chile 3 CEA/I2BM/SHFJ/LIME, Orsay, France 4 IMNC, IN2P3, UMR 8165 CNRS-Universites Paris 7 Paris 11, Orsay, France 2

Positron Emision Tomography (PET) images are inherently affected by noise and low spatial resolution that may lead to incorrect estimations of the real uptake of the radiotracer in tissues. A new method for enhancing the signal-to-noise ratio (SNR) of dynamic PET images is presented. The proposed method is a coupled 4D diffusion and shock filtering scheme based on a weighted structure tensor of the vector-valued image. We exploit the spatial and temporal information along the entire sequence to reduce noise and sharpen boundaries between kinetic regions. The method does neither require knowledge of the point spread function of the system (PSF) nor prior anatomical support. Comparative experimentations on realistic GATE Monte Carlo simulations validate the potential of the proposed method. M18-51, Guided Noise Reduction with Streak Removal for High Speed Perfusion C-Arm CT M. T. Manhart1, A. Aichert1,2, M. Kowarschik3, Y. Deuerling-Zheng3, T. Struffert2, A. Doerfler2, A. K. Maier1, J. Hornegger1 1

Pattern Recognition Lab, University of Erlangen-Nuremberg, Erlangen, Germany Department of Neuroradiology, University of Erlangen-Nuremberg, Erlangen, Germany 3 Angiography & Interventional X-Ray Systems, Siemens AG, Forchheim, Germany 2

Tissue perfusion measurement using C-arm angiography systems capable of CT-like imaging (Carm CT) is a novel technique with high potential benefit for catheter-guided treatment of stroke in the interventional suite. New high speed protocols (HSP) with increased C-arm rotation speed enable fast acquisitions of C-arm CT volumes and allow for sampling the contrast flow with improved temporal resolution. However, the peak contrast attenuation values of brain tissue typically lie in a range of 530 HU. Thus perfusion imaging is very sensitive to noise. Recently we introduced the FKD-JBF denoising technique based on Feldkamp (FDK) reconstruction followed by denoising in volume space using joint bilateral filtering (JBF). In the evaluation FDK-JBF achieved comparable results to fully iterative techniques, e.g. the iTV algorithm, but is computationally less costly. However, the angular sampling of the projection data in the HSP is coarse, which leads to streak artifacts in the reconstructed volumes. Since mask volumes are subtracted from the contrast enhanced volumes to compute the pure contrast enhancement, the 685

streak artifacts are subtracted out. But if the patient moves during the acquisition, the streak artifacts will not be identical in the mask and contrast enhanced volumes and visible in the pure contrast volumes. We show that these streaks can lead to sever artifacts in the perfusion maps and describe a novel technique for streak removal (SR), which is based on streak detection by using time-contrast curve analysis and total variation. We evaluate the SR using digital brain phantom and real clinical patient data. The results show that streaks can be successfully removed. The correlation of the reconstructed blood flow maps to the ground truth in the simulation study increases from 0.69 to 0.78 if SR is applied. In the patient study our algorithm produces similar maps as the iTV algorithm, but ~10 times faster. M18-52, A Novel Image Restoration Method Assisted by Reference Image in Dual-Energy CT Y. Li1,2, L. Zhang1,2, J. Hao1,2, K. Kang1,2 1 2

Department of Engineering Physics, Tsinghua University, Beijing, China Key Laboratory of Particle & Radiation Imaging, Ministry of Education, Beijing, China

By scanning with two distinguished X-ray energies, dual-energy CT (DECT) can provide the effective atomic number image and electron density image of the scanned object besides traditional attenuation images. DECT becomes more and more important in security inspection, medical diagnosis and other industrial areas. All the images acquired in DECT should have strictly the same structures and edges, as they represent the same object. However, due to the noise and errors in dual-energy projection decomposition, the image quality of the effective atomic number reconstructed from DECT is always far from satisfaction. In this paper, we propose a novel image restoration method based on a reference image. In DECT image processing, the attenuation image serves as the reference image, while the effective atomic number image is the target image. The weight is derived from the reference image first. Then, average the pixels with the weights in the target image to obtain the restored image. Different methods of weight calculation can be utilized. Two experiments were conducted to prove that can the proposed restoration method can effectively reduce the artifacts and noise of the effective atomic number image with the help of high-quality attenuation reconstruction. M18-53, Registration Between Respiratory-Gated PET/CT and High-Resolution CT with XCAT Simulations: Evaluation and Optimization for Subsequent PVC A. Turco1, J. Nuyts1, O. Gheysens1, J.-U. Voigt2, P. Claus2, K. Vunckx1 1 2

Dept. of Nuclear Medicine, KU Leuven, Leuven, Belgium Dept. of Cardiology, KU Leuven, Leuven, Belgium

Matching PET/CT to high-resolution CT is a well-established way to improve PET image quality, through the application of prior information during reconstruction. In cardiac imaging, however, the presence of both cardiac and respiratory motion can compromise accurate alignment, thus hampering exact myocardial quantification and diagnosis. Usually, PET/CT images are corrected for attenuation using an average attenuation map obtained from a low-dose CT scan, before being registered to the high-resolution CT. Although this average map has been shown to have little influence on artefact production in the cardiac region, nothing has been said so far on the influence of the use of an average attenuation correction map for inter-modality registration purposes. The 686

aim of this work is to assess the effect of attenuation correction on the quality of image registration between respiratory-gated cardiac PET/CT images and high-resolution CT images. Influence of cropping images to the heart region, and of the use of contrast-enhanced CT images, is also evaluated. Results are illustrated via means of simulations, using a realistic digital phantom (XCAT) in which only breathing motion was modelled. The so generated PET/CT respiratory frames are rigidly registered to the high-resolution CT, using normalized mutual information as the matching criterion. Registration quality was measured in terms of overlap between the leftventricular regions of target and registered images, using DICE-Srensen coefficient as figure of merit. Deep and shallow motion patterns were compared. Results show a clear improvement in registration quality when a perfect attenuation correction map is used instead of an average one. Cropping images to the heart region seems to be anyway essential for an acceptable image alignment. Further improvements can be achieved with the use of contrast-enhanced CT. Non rigid registration, however, seems necessary to obtain accurate overlap between PET and CT images. M18-54, PET/CT Image Denoising and Segmentation Based on a Multi Observation and Multi Scale Markov Tree Model H. Hanzouli1, J. L. Lahorgue1, E. Monfrini2, G. Delso3, W. Pieczynski2, D. Visvikis1, M. Hatt1 1

INSERM UMR 1101, LaTIM, Brest, France Tlecom Sud-Paris, CITI, CNRS UMR 5157, Evry, France 3 Department of Medical Imaging, University Hospital, Zurich, Switzerland 2

This work deals with a Markov model as a probabilistic quad-tree graph (Hidden Markov Tree, HMT). Our motivation for using such a model is to provide fast computation, improved robustness and an effective interpretational framework for image analysis and processing in oncology. Thanks to two efficient aspects (multi observation and multi resolution) of HMT and Bayesian inference, we exploited joint statistical dependencies between hidden states to handle the entire data stack. This new flexible framework was applied first to mono modal PET image denoising taking into consideration simultaneously the Wavelets and Contourlets transforms through multi observation capability of the model. Secondly, the developed approach was tested for multi modality image segmentation in order take advantage of the high resolution of the morphological computed tomography (CT) image and the high contrast of the functional positron emission tomography (PET) image. On the one hand, the results of denoising using the proposed model with respect to wavelet denoising, currently considered as the state-of-the-art filter in PET, are promising. Denoising performed through the wavelet-contourlet combined multi observation HMT led to the best trade-off between denoising, resolution loss and quantitative bias. On the other hand, PET/CT segmentation's results performed with the proposed HMT led to a reliable tumor segmentation taking advantage of the CT's anatomic classification and the strength of PET when classifying diseased tissues. Future work will investigate the potential of the HMT for PET/MR image segmentation and analysis. Moreover, we will use Pairwise Markov Tree (PMT) and evidence theory as an added value in addition to the use of PET multi-tracer information. Keywords: Positron Emission Tomography (PET), Computed Tomography (CT), Bayesian inference, Hidden Markov Trees (HMT), Wavelet and Contourlet analysis M18-55, A 4D CT Volumetric Image Automated Segmentation and Registration Method for Lung Tumor 687

M. R. Alnowami1, M. E. Al-Sulimane2, S. M. Al-Batati1, K. Wells3 1

Faculty of Engineering, King Abdulaziz University, Jeddah, Saudi Arabia Physics Department, Taif University, Taif, Saudi Arabia 3 Center for Vision, Speech and Signal Processing,, University of Surrey, Guildford, UK 2

In this study, a fully automated system has been developed to segment, register and localize the 3D lung tumor positions across all respiratory data in the 4D CT datasets. Automated tumor isolation is carried out for each slice of a first phase of the 4D CT volumetric images using active contour methods. A lung tumor segmentation is performed using a combination of active contours, similarity of intensity pixels and geometric analysis. Then, an intensity based registration based on a 12 degrees of freedom of an affine transformation is used to localize the tumor 3D potion across all next phases in the 4D CT volumetric images. The preliminary results obtained from the proposed 4D CT Volumetric Image Automated Segmentation and Registration algorithm shows a promising results to segment and register lung tumor in a 4D CT data. The average registration error across simulated data was 9+-7 mm. M18-56, Extraction of Cervical Vertebrae from Panoramic X-Ray Images J. Yamamoto1, M. Yanase1, K. Ogawa1, A. Katsumata2 1 2

Graduate School of Engineering, Hosei University, Tokyo, Japan School of Dentistry, Asahi University, Gifu, Japan

The purpose of this study is to remove the cervical vertebrae from a dental panoramic x-ray image with a tomosynthesis method. The elimination of the cervical vertebrae is based on the concept of the tomosynthesis method. We first measured the shift-amount that was required to reconstruct a panoramic x-ray image of the dental arch with a calibration phantom. Then, we also measured the shift-amount that was required to reconstruct the cervical vertebrae. With these data, we reconstructed the focused image of the dental arch and cervical vertebrae. These two images were processed with the blurring functions defined at each focusing geometry of the above images, and the true image of the dental arch without the shadow of the cervical vertebrae was obtained. Our proposed method was evaluated with clinically measured data. The results of the experiments showed that our proposed method was remarkably effective in removing the shadow of the cervical vertebrae. M18-57, Anatomical Segmentation for Temporal Subtraction Images in Successive Whole-body Bone Scans J. Shiraishi1, S. Shiraishi2, K. Kawakami3, T. Hosoya3 1

Medical Physics/Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan Diagnostic Imaging/Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan 3 Product Management & Marketing Dept./Sales & Marketing Div., FUJIFILM RI Pharma Co., Ltd., Tokyo, Japan 2

We have developed a computerized scheme for a temporal subtraction (TS) image in successive whole-body bone scans and demonstrated the clinical utility of this scheme in the prospective clinical study. Recently, bone scan index (BSI) has been used for the quantitative analysis of bone metastases. The calculation of BSI requires anatomical segmentations for applying the weight 688

fraction. In this study, in order to evaluate a change of BSIs in successive whole-body bone scans, an anatomical segmentation scheme was incorporated into the temporal subtraction image. Total of 300 cases of successive bone scans in which each case includes a pair of two images for anterior and posterior whole body views, were corrected retrospectively with the following inclusion criteria; 1) at least one abnormal finding in either view, and 2) a maximum number of 20 interval changes. We used 100 cases for training computerized scheme and the remains for the independent test. For the computerized scheme of an anatomical segmentation, one normal case (the standard case) was initially selected to create a standardized image in each view. Each of the standardized images for anterior and posterior views was produced by averaging all training images in which the size, orientation, and location of a skeletal region in a bone scan image were adjusted to those of the standard case by using a linear interpolation. Templates of seven anatomical regions, such as skull, ribs, thoracic vertebrae, lumber vertebrae, pelvis, upper arms, and femurs, were determined manually on the standardized image. A number of parameters for adjusting a current image to the standard image were applied to the templates of anatomical regions to fit those regions into the previous, current and TS image. Preliminary result obtained from 143 test cases (286 TS images) indicated that 99.3% (284/286) of temporal subtraction images were correctly segmented anatomically by use of this proposed method. M18-58, Contourlet-Based Deformable Model for Tumor Volume Delineation in PET M. Abdoli1, R. A. J. O. Dierckx1, H. Zaidi1,2 1 2

Nuclear medicine and molecular imaging, University Medical Center Groningen, Groningen, Netherlands Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva, Switzerland

PET-guided radiation therapy treatment planning, clinical diagnosis, assessment of tumor growth and therapy response rely on the accurate delineation of the tumor volume and quantification of tracer uptake. Most PET image segmentation techniques proposed so far fail in the presence of heterogeneity of tracer uptake within the lesion. This work presents an active contour model-based on the method of Chan and Vese (2001) designed to take into account the high level of noise and to handle the heterogeneity of tumor uptake typically present in PET images. In the proposed method, the fitting terms in Chan-Vese formulation are modified by introducing new input images, including the smoothed version of the original image using anisotropic diffusion filtering (ADF) and the contourlet transform of the image. The proper choice of the energy functional parameters has been formulated by making a clear consensus based on tumor heterogeneity and TBR levels. The algorithm was evaluated using simulated phantom and clinical studies. The proposed technique was also compared to a number of previously reported image segmentation techniques. The results were quantitatively analyzed using three evaluation metrics, including the spatial overlap index (SOI), the mean relative error (MRE) and the mean classification error (MCE). In the largest clinical group comprising nine datasets, the proposed approach improved the SOI from 0.410.14 obtained using the best performing algorithm to 0.540.12, and reduced the MRE from 54.23103.29 to 0.1916.63 and the MCE from 112.8669.07 to 60.5818.43. The proposed segmentation technique is superior to other representative segmentation techniques in terms of highest overlap between the segmented volume and the ground truth/histology and minimum relative and classification errors. Therefore, the proposed active contour model can result in more accurate tumor volume delineation from PET images. M18-59, Improved PET Lesion-Detection Performance Using 2mm Pixels 689

A. M. Morey, F. Noo, D. J. Kadrmas UCAIR, University of Utah, Salt Lake City, UT, United States

Positron emission tomography (PET) images are typically reconstructed with an in-plane pixel size of ~4mm for cancer imaging. The objective of this work was to evaluate the use of smaller pixels for the task of detecting focal warm lesions in a noisy structured background. Experimental phantom data from the Utah PET Lesion Detection Database was used, modeling whole-body oncologic FDG PET imaging of a ~92kg patient. The data comprised 24 scans over 4 days on a Biograph mCT TOF PET/CT scanner, with up to 23 lesions (diam. 616mm) distributed throughout the thorax, abdomen, and pelvis each day. Images were reconstructed with 2.036mm and 4.073mm pixels using ordered-subsets expectation-maximization (OSEM) both with and without point spread function (PSF) modeling and time-of-flight (TOF). Detection performance was assessed using the channelized non-prewhitened (CNPW) numerical observer with localization receiver operating characteristic (LROC) analysis. The observer was first used to optimize the number of iterations and smoothing filter for each case. Tumor localization performance and the area under the LROC curve (ALROC) were then analyzed as a function of pixel size. In all cases, the images with ~2mm pixels (ALROC = 0.59[OSEM], 0.60[PSF], 0.65[TOF] and 0.66[PSF+TOF]) provided significantly higher detection performance than those with ~4mm pixels (ALROC = 0.56, 0.57, 0.61 and 0.63, respectively). The degree of improvement from using ~2mm pixels was larger than that from PSF modeling for these data, and provided roughly half the benefit of using TOF. Notably, all three effects cumulatively improved performance, and PSF+TOF reconstruction with 2mm pixels offered the best performance. This study suggests that a significant improvement in lesion-detection performance for general oncologic PET imaging can be attained by using smaller pixel sizes than current typical practice. The primary drawback is a ~4x increase in reconstruction time and data storage requirements. M18-60, A Naive-Bayes Numerical Surrogate for a Human Observer in Perfusion Detection and Localization in SPECT-MPI F. M. Parages1, J. M. O'Connor2, P. H. Pretorius2, J. G. Brankov1 1 2

Electrical and Computer Eng. Department, Illinois Institute of Technology, Chicago, IL, United States Department of Radiology, University of Massachusets Medical School, Worcester, MA, United States

In medical imaging it is widely accepted that diagnostic image-quality should be assessed through the diagnostic-task performance of human observers (HumOs). For these evaluations, mathematical algorithms known as model observers (MOs) are often used as a substitute for HumOs studies in early stages of image reconstruction algorithm development. Diagnostic tasks in SPECT myocardial perfusion imaging (MPI) involve localization and evaluation of regions with abnormal myocardial perfusion. In this work we propose a new model observer for localization and assessment of perfusion defects. This MO is based on a naive-bayes classifier (NB-MO). In the proposed approach the NB-MO is applied over a set of image features extracted from SPECT polar-maps, aiming to predict perfusion scores given by HumOs for each myocardium region. Our HumO pool is comprised of five experienced (physicians) readers, who scored location and severity of perfusion defects in 179 simulated SPECT-MPI cases and two different reconstruction methods (FBP and OSEM). Preliminary results show good agreement between performances of HumOs and the proposed NB model observer, as well as MO excellent generalization between different reconstruction methods. 690

M18-61, A Novel Scheme for Computer Aided Detection (CADe) of Colonic Polyps Based on Colon Structure Decomposition H. Wang1, Z. Liang2, H. Peng3, B. Song2, F. Han2, H. Han2, Y. Liu2 1

School of Software,Beihang University, Beijing, China Dept. of Radiology, Stony Brook University, Stony Brook, New York 3 Dept. of Computer Science, Stony Brook University, Stony Brook, New York 2

To more accurately detect small polyps( ranged 5~8mm,also called C2 stage) on the colon wall is of great significance for early diagnosis colorectal cancers. Since the colon usually consists of the mucosa layers which result in Partial volume effect(PVE) on the colon wall, the task turns too complicated to be reached by simply following solo philosophy. According to the literature, the sensitivity of detection for small polyps only slightly above 0.83( polyp size range 5~9mm). We believe that due to the influence of background undulating, small polyps and large polyps(bigger than 8mm) usually have not only some differences in the size of the shape, but also significant difference on the geometric morphology. In order to adapt previous method to the mission of the small polyps' detection, a novelty global structure decomposition approach was suggested. By which the complex colon was separated into much uniform broken parts, where the Haustral folds and Haustral wall were broken into two independently kinds of morphological shape by means of analysis on second order derivatives of volume image. Polyp detection will look like finding certain abnormal protrusion on the relatively simple morphological surfaces. Hence the morphologically protruding characteristic of the small polyps will be enhanced in the volume image. Experimentally, we chose 140 patient cases from our CTC database, and in which we focus on the polyps whose size range from 5~8mm to validate the presented new approach. Compared with previously presented in the literature, the experimental results are much more promising with average sensitivity of 0.99 per patient. At mean time the false positive rate dramatically decreased to 1.2 per patient after false positive deduction based on the textures. M18-62, Detection of Temporal Events in Colonoscopy Videos Using Motion Vector Templates J. Oh1, R. Nawarathna1, W. Tavanapong2, J. Wong2, P. C. de Groen3 1

Department of Computer Science and Eng., University of North Texas, Denton, TX, USA Computer Science Department, Iowa State University, Ames, IA, USA 3 Mayo Clinic College of Medicine, Rochester, MN, USA 2

In recent studies several metrics for measuring quality of Colonoscopy are proposed and implemented in real-time software systems. The location of phase boundary between insertion and withdrawal phases, and the amount of circumferential inspection are essential for generating such quality metrics, and can be determined by analyzing various camera motions of Colonoscope. This paper studies the estimation of the camera motions of Colonoscope using motion vector templates. The experimental results show that we can estimate the camera motions very accurately using motion vector templates so that we can find the location of phase boundary and the amount of circumferential inspection. M18-63, Whole-Body MR-Based Attenuation Correction Map with Fat Segmentation in Abdominal Scan 691

H. J. An1, H. J. Im1, I. C. Song2, E. S. E. Kim3, D. S. Lee1, J. S. Lee1 1

Department of Nuclear Medicine, Seoul National University College of Medicine, Seoul, Korea Department of Radiology, Seoul National University College of Medicine, Seoul, Korea 3 Department of Nuclear Medicine, UC Irvine, Irvine, CA, USA 2

Attenuation correction is a prerequisite procedure in quantitative PET imaging. Because of some technical difficulties, many researches are focusing on MR-based attenuation correction. For whole-body PET/MR, 2-point Dixon MR sequence was proposed to classify soft and fat tissue. However, the current approaches had difficulties to generate automatic accurate attenuation map. In addition, it has been observed that visceral adipose tissue (VAT) showed higher FDG uptake compare to subcutaneous adipose tissue (SAT). Considering these results, we propose the potential MR-based attenuation map with fat segmentation. It was implemented by a fully automated method that uses Dixon sequence in combination with a level set algorithm to derive attenuation maps for whole-body PET in abdominal region. M18-64, The Correct Configuration of Retinal Vessels in Retinal Images T. Ahmad Dept. of Computer Science, University of Lincoln, Lincoln, Lincolshire, United Kingdom

The correct configuration of broken vessels in vessels-segmented retinal images is an important step for classification of vessels, analysis of retinal landmarks and diagnoses of cardiovascular diseases in retinal images. A single mistake during reconnecting process of broken vessels can result in a completely wrong retinal vasculature. The complexity increases in the presence of nosiness (Vessels-Like data), abnormal vessels, and insufficient vessel features. Furthermore, there arent exist fixed rules for the correct joining of broken retinal vessels; except few physiological rules that help establishing likelihood to a particular joining decision. In this paper a decision support system (DSS) based on the supervised-learning and statistical model is proposed; that optimally configures the broken vessels at retinal junctions. The method is carried out by training the data through supervised learning and establishing a probability model followed by the experiments and analysis process. The most frequently used image-set by research community, DRIVE (Digital Retinal Images for Vessel Extraction) is used for the training, experiment and analysis purpose. A number of significant vessel features are extracted at 500 junctions (terminals, bifurcations and crossings) from the DRIVE training set. The selected features helped determining similarity measure among broken vessels. The probability distribution functions are produced by representing the vessel feature distributions to highly appropriate parametric/non-parametric statistical models. An experiment is performed on DRIVE test set; using the probabilities, based on the pdfs (produced in first step) for all the joining possibilities. A comparison of the outcome with the gold standard set of DRIVE is done; and with a minor compromise, it offers the research community with a highly satisfactory result. M18-65, PET/CT Image Textures for the Recognition of Tumors and Organs at Risk for Radiotherapy Treatment Planning G. Liu1, W. Yang1, S. Zhu2, Q. Huang3, M. Liu1, H. Wu1, Z. Hu1, Z. Huang2, Y. Yuan2, K. Liu2, W. Huang1, B. Liu1, J. Liu1, X. Zhao1, M. Nie1, B. Hu2, J. Zhang2, Y. Mo2, B. Zeng2, X. Peng2, J. Zhou2

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College of Electrical and Information Engineering, Hunan University, changsha, China Departments of Radiation Oncology, Medical Physics and PET/CT Center, Cancer Hospital of Hunan province, Xiangya School of Medicine of Central South University, Changsha, China 3 School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China 2

Positron emission tomography/computed tomography (PET/CT) images have been used in the radiotherapy treatment planning, especially in the delineations of biological target volumes (BTVs) of tumors. However, it is not possible to accurately and precisely discriminate between tumors and adjacent normal tissues in PET/CT images if the normal tissues with a high PET standard uptake value (SUV) such as brain stem and other brain tissues that are close to the tumors, or if the sub-clinical tumor volumes with a low SUV are encompassed by normal tissues also with a low SUV. CT image has relatively poor soft tissue contrast and many malignant tumors arise from within soft tissue. Therefore there is little distinction between the CT HU/numbers of tumors and the surrounding normal tissues. To accurately and precisely distinguish tumors from adjacent normal tissues, and to spare organs at risk (OARs) in radiotherapy treatment planning, we extracted the PET coarseness and busyness, and CT contrast and coarseness respectively from the neighborhood gray-tone-difference matrices of co-registered PET SUV/CT HU images of tumors. We found that PET busyness and contrast can provide more accurate and precise complementary information for the recognition of tumors than PET SUV, while CT coarseness and contrast can offer useful complementary information for the discrimination of organs at risk. Therefore, we proposed to delineate the OARs based on CT coarseness, CT contrast and PET busyness by an adaptive 3D volume growing method with two growing stages to best spare the OARs. Moreover, we proposed to delineate the BTVs based on PET SUV, busyness, and contrast by an hierarchical Mumford-Shah Vector Model via a refined ring-VOI based on the delineated OARs. Four patient studies were assessed and visually inspected by radiation oncologists. The resulting BTVs were more accurate and more precise, and better spared the OARs than our previous BTVs. M18-66, Analysing Morphological Patterns of Blood Vessels for the Detection of Alzheimers Disease M. Sahrim1, M. Nixon1, R. Carare2 1 2

Electronics and Computer Science, University of Southampton, Southampton, UK Medicine, University of Southampton, Southampton, UK

The physiological consequences of Alzheimers disease (AD) concern the development of amyloid plaques and neurofibrillary tangles. Development of amyloid plaques in the brain is caused by Amyloid Beta that forms part of an amyloid precursor protein. In a normal brain, these protein fragments are broken down and eliminated but with AD, these fragments accumulate to form hard insoluble plaques. Our techniques are based on the image analysis of brain tissue and study the branching structures of the blood vessels (which is novel itself), on the analysis of tortuosity and density. These are known to have links with the onset of AD. The branching structures are detected by evidence gathering approaches and described by their structure. This allows recognition to be achieved: the structure of those samples derived from patients with AD differs from that for normal subjects. This also occurs for the tortuosity and to a lesser extent the density. The descriptions can be classified using machine learning techniques, as such achieving an automated process from image to recognition. We analyse the structure of the blood vessels in a database of images collected from control, age-matched and patients with severe AD. The 693

database comprises five subjects of each of the three types, imaged in controlled conditions and from the Brain Tissue Resource of Newcastle UK. We show that by automated image analysis we now appear able to discriminate between brain tissue samples from patients presenting AD and from the normal samples. The branching structure is the description that is most suited to classification purposes. On this initial dataset we can achieve 100% correct classification from a combination of these descriptions and around 90% correct classification from the branches and their paths. We are thus confident in the correct referral of patients for further investigation when this new technique is translated for clinical use. M18-67, An Optimal Framework for Surface-Based [11C] PIB PET Mapping Using MRI-Based Cortical Surface Analysis with Partial Volume Correction C. M. Kim, H. J. Yun, J.-M. Lee Biomedical Engineering, Hanyang University, Seoul, Republic of Korea

11C PIB PET has been widely applied to the in vivo assessment of β-Amyloid plaque deposition, which associated with progress of pathology in Alzheimers disease. Previously, PIB PET studies had based on ROI analysis or VBM analysis which depends on the selected regions and accuracy of spatial normalization into standard space. After that, several surface based analysis were proposed to compensate for mis-registration and improved smoothing effect but were not applied for PIB PET studies. In this study, we proposed an optimal framework for surface based PIB PET mapping using MRI-based cortical surface analysis with partial volume correction (PVC) by MR derived probability maps. We compared with proposed mapping and conventional VBM analysis. To find an optimal method, comparison of with and without PVC had also performed. All of subjects were recruited from the Alzheimer's Disease Neuroimaging Initiative which constitute 20 cognitively normal, 70 MCI and 15 AD patients. To mapping onto the cortical surface, we reconstructed hemispheric cortical surfaces which consisted of a triangular mesh using standard MNI anatomical pipeline. In PIB PET, each individual image was co-registered into corresponding native MR image and created a DVR image which scaled using the mean value in the cerebellum. Subsequently, the PIB DVR value in each vertex was calculated according to each column line between outer GM vertex and corresponding WM vertex by the interpolation algorithm in native MR space. In addition, we performed surface-based PVC using GM probability maps derived from native T1 images. We performed two sample t-test between three groups which constructed AD-NC, AD-MCI and MCI-NC. The result shows that all between-group paired comparisons revealed more significant difference when used to our method than VBM analysis. Besides, using our method with PVC affects not only the patterns of group differences but also increased the statistical significance than without PVC. M18-68, Spectral Unmixing for in Vivo Fluorescence Imaging Based on Accurate Target-toBackground Estimation C. Hu, Y. Zhao, B. Qin School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China

Spectral unmixing is a useful technique in fluorescence imaging for reducing the effects of background fluorescence (BF), also called autofluorescence(AF), and separating multiple 694

fluorescence probes. But it is complicated by the significant overlap of the fluorophore emission spectra, and the strong BF signal is often highly mixed with all multi-target fluorescences and can have a confusing effect on the measurement of the multi-target fluorescences. In this work, we introduce a spectral unmixing algorithm tailored for in-vivo optical imaging, which effectively separates the multi-target fluorescence from the BF without any hardware-based BF acquisition or a-priori knowledge of in-vitro spectra. First, we use kernel maximum autocorrelation factor analysis (kMAF) to accurately detect and separate multitarget fluorescence regions from the BF in sparse multispectral observation data. The observation data being outside of the target regions can be regarded as only containing BF, so we can get accurate spectral estimation of the BF. With the accurate target-to-background fluorescence estimation, the multi-target fluorophores and AF could be easily unmixed using multivariate curve resolution-alternating least squares method (MCRALS). M18-69, Classification Initialized Hierarchical ALS-Based NMF with Partial Sparseness Constraints for Fluorescence Spectral Unmixing S. Huang, C. Hu, B. Qin School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China

Nonnegative Matrix Factorization (NMF) is widely used in the spectral unmixing of fluorescence imaging, which decomposes the mixed fluorescence components into a set of constituent spectra and their corresponding fractional abundances. However, NMF is a nonconvex programming in the iteration process, thus the solution depends on the initial values and some physical constraints (such as sparseness constraints) and consequently not unique. In this paper, considering the autofluorescence (AF) and multi-target fluorophores having different characteristics of spectral and spatial distribution, we initialized NMF by using the normalized cut method, which can roughly classify all pixels into two groups: one for multi-target fluorophores and the other for AF. Therefore the spectra of multi-target fluorophores and AF can be initialized with the spectral signals in the corresponding groups. Partial sparseness constraints are further imposed on the hierarchical alternating least squares (HALS)-based NMF, which only introduce sparsity into the abundances of multi-target fluorophores with the exception of autofluorescence. Based on these classification-based initialization and partial sparseness constraints for the different components of fluorescence imaging, the multi-target fluorophores are clearly discriminated from AF in the solution of NMF. By using simulated and in vivo experimental data, the performance of the proposed algorithm has been validated as the best compared with several other state-of-the-art methods. M18-70, Development of Experimental and Image Database System for Molecular Imaging Research H. Watabe1, G. Horitsugi2, T. Watabe2, H. Kato2, E. Shimosegawa2, J. Hatazawa2 1 2

Division of Radiation Protection & Safety Control, Tohoku University, Sendai, Japan Osaka University Graduate School of Medcine, Suita,Osaka, Japan

Hospital information system (HIS),Radiology information system(RIS) and Picture archiving and communication system(PACS) have long history and are well established infrastructure in 695

hospital. In molecular imaging research, researchers utilize several imaging modalities such as PET, SPECT, optical imaging, MRI, and their demands for central image storage and information database have been raised for a long time. However, due to conceptional differences for organizing data between daily hospital routines and molecular imaging studies, no conventional HIS/RIS/PACS systems fit the researchers' requisitions. We developed MIBASE, experimental and image database system for molecular imaging research. The MIBASE records all information regarding experiments such as subject conditions, experimental protocol, notification so on, and store acquired images by several imaging modalities. File formats stored in the MIBASE are arbitrary, and any image data will be exported to a PACS server by converting data of any format into DICOM format. The MIBASE can be accessed by any Web browser through Internet, thus, it is possible to remotely retrieve data and experimental records. Experimental records and images are shared among researchers who have participated experiments under a research group. Access control mechanism is also introduced to protect data owned by a group from other groups. The system runs on a Linux base workstation (Intel Xeon CPU 2.93 GHz;8 GBytes memory) and most of software codes are written in Python script language with Pylons web framework. The MIBASE offers the infrastructure for molecular imaging researches, which results in well organized data management and rapid achievement of scientific outcomes. M18-71, DQS Advisor: a Visual Interface to Balance Dose, Quality and Reconstruction Speed in Iterative CT Z. Zheng, E. Papenhausen, K. Mueller Computer Science, Stony Brook University, Stony Brook, US

Low-dose CT has recently shown much progress in its mission to deliver clinically-useful results with reduced radiation imposed on patients. However, for many of the proposed reconstruction algorithms there is still no quantitative link between the settings of the various parameters and the corresponding reconstruction image quality and reconstruction time. As a solution, we propose to combine automatic optimization with human interaction. We developed an interactive visual parameter space navigation interface which assists users in the selection of data acquisition and iterative CT algorithm parameter settings and allows them to intuitively decide among trade-offs. The optimization component is based on our previous parameter optimization framework. We now focus on the visual interface and conduct a study across different data acquisition settings in terms of X-ray tube current and number of projections. The user interface presents the performance data as color-mapped 2D scatter plots and it also provides a gallery feature that allows a qualitative comparison of possible reconstruction results. Our system is embedded into a webpage and can be accessed via a web browser from any-where and any common computer platform. Further efforts focus on the scalability of our approach, in order to make it applicable to realistic application scenarios.

**************** M19 (8) ****************************** M19 Student Competition Friday, Nov. 1 14:00-16:00 GBR 101-102 696

Session Chair: Vesna Sossi, University of British Columbia, ; John Aarsvold, Atlanta Veterans Affairs Medical Center & Emory University, United States

(14:00) M19-1, Investigation of the Effects of Scintillator Pixel Shape, Surface Treatment and Optical Coupling on the Performance of Si-PM Based BGO Detectors Y. Valenciaga, D. L. Prout, A. F. Chatziioannou Department of Molecular and Medical Pharmacology, Crump Institute for Molecular Imaging, UCLA, Los Angeles, CA, USA

Positron Emission Tomography (PET) is based on the detection of annihilation photons through their interactions with scintillator crystals. Traditionally, detection of scintillation light is achieved with multi-anode photomultipliers that have low noise and high gain but are bulky and have limited quantum efficiency. The new generation of solid state light detectors (SiPMs) offers similar gain with packaging advantages, but at the expense of increased device noise per surface area. Reliable triggering of solid state photodetectors requires robust identification of a scintillation pulse, above the device dark current. Triggering becomes challenging, when the scintillator pixel geometry becomes elongated with a large aspect ratio, as is required for high resolution imaging. Furthermore, BGO produces less overall scintillation light, spread over a longer pulse time for each detected annihilation, compared to LSO and its variants. A considerable fraction of scintillation light experiences multiple internal reflections, becoming trapped and absorbed before it can exit towards the detection surface. To address this issue, with the view of designing high resolution preclinical PET, we examined the performance of different scintillator geometries, surface treatments and interface material index of refraction for BGO crystals, coupled to solid state photodetectors. Simulations were performed by a Monte Carlo based software (SLITRANI). In addition, the energy spectra for different crystal geometries were obtained through measurements of individual crystals coupled to a solid state photodetector. In agreement with previous work, preliminary results indicate an advantage of slanted geometries over conventional rectangular crystal shapes for light extraction and energy resolution. Consequently, these geometries are expected to improve event triggering in the detector, although the energy resolution might become more dependent on the location of event interaction. (14:15) M19-2, First Performance Tests of Digital SiPMs in Prompt Gamma Imaging with a Knife-Edge Slit Camera for Proton Range Verification P. Cambraia Lopes1,2,3, E. Clementel4, P. Crespo2,5, S. Henrotin6, J. Huizenga1, G. Janssens6, K. Parodi7,8, D. Prieels6, F. Roellinghoff6, J. Smeets6, F. Stichelbaut6, D. R. Schaart1 1

TNW/RST/RIH, Delft University of Technology, Delft, The Netherlands LIP-Coimbra, Laboratrio de Instrumentao e Fsica Experimental de Partculas, Coimbra, Portugal 3 Heidelberg Ion-Beam Therapy Center, University Clinic of Heidelberg, Heidelberg, Germany 4 iMagX Project, ICTEAM Institute, Universit Catholique de Louvain, Louvain-la-Neuve, Belgium 5 Physics Department, Universidade de Coimbra, Coimbra, Portugal 6 Ion Beam Applications SA, Louvain-la-Neuve, Belgium 7 Department of Radiation Oncology, Heidelberg University Clinic, Heidelberg, Germany 8 Department of Medical Physics, Ludwig Maximilian University, Munich, Germany 2

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Real-time particle range monitoring may facilitate online adaptive particle therapy (OAPT) with pencil-beam scanning systems. Imaging of the prompt gamma (PG) rays emitted during proton irradiation is currently under investigation as a tool for range monitoring. In this work, we present an initial performance test of two gamma camera prototypes based on digital silicon photomultiplier (dSiPM) arrays for PG imaging through a knife-edge slit collimator. The dSiPM concept was introduced by Philips Digital Photon Counting (PDPC) and recently developed into a modular design. For this purpose we have acquired collimated PG emission resulting from irradiation of a PMMA target with proton pencil beams with energy of 160 MeV, using both BGO- and LYSO-based (pixelated) detector modules, each consisting of 2x2 DPC3200-22-44 dSiPM arrays. Moreover, for the LYSO-based modules, we were able to apply TOF discrimination by synchronizing the dSiPMs readout electronics with the 106 MHz radiofrequency (RF) signal of the cyclotron. From the collected data, we observed fall-off profiles that are correlated to the Bragg-peak (BP) at various positions relative to the slit opening, for both detector modules, by applying energy discrimination only. First results on time-of-flight (TOF) spectra confirm a clear correlation of detected events with the time structure of the beam delivery, which emphasize the potential use of this detectors for rejecting background events by using TOF. A detailed quantification study of the signal-to-noise ratio and range estimation accuracy with and without applying TOF discrimination will be presented at the conference. (14:30) M19-3, Test of a Compton Imaging Prototype at the ELBE Bremsstrahlung Beam F. Hueso-Gonzalez1, C. Golnik1, M. Berthel1, A. Dreyer1, W. Enghardt1,2, F. Fiedler2, K. Heidel2, T. Kormoll1, H. Rohling1, S. Schoene2, R. Schwengner2, A. Wagner2, G. Pausch1 1

OncoRay - National Center for Radiation Research in Oncology, University Hospital TU Dresden, Dresden, Germany 2 Institute of Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany

In the context of hadron therapy, particle range verification is a major challenge for the quality assurance of the treatment. One approach is based on the measurement of the prompt gamma rays resulting from the tissue irradiation. A Compton Camera based on several planes of 3D position sensitive gamma detectors, together with an image reconstruction algorithm, is expected to measure the prompt gamma emission profile, which is correlated with the dose distribution. At Helmholtz-Zentrum Dresden-Rossendorf and OncoRay, a camera prototype has been developed consisting of 2 scatter planes (CZT-strips) and 1 absorber plane (LSO block). The data acquisition is based on VME electronics, which is handled by software developed on the ROOT platform. The prototype was tested at the linear electron accelerator ELBE of our research center. The spectrum of the bremsstrahlung gamma rays produced there has similarities with the one expected in the clinical case (proton cyclotron, also pulsed), and the setup allows us to test the imaging algorithms, as the bremsstrahlung beam can be considered as an ideal point source. The measured energy deposition spectrum is in good agreement with the simulated one. In addition, the timecorrelation between the pulsed prompt gamma rays and the measured signals was used for discriminating background events, thanks to the time resolution of the detectors of around 3 ns. We conclude that the detectors are suitable for time-resolved background discrimination in pulsed clinical particle accelerators (e. g. cyclotrons). Ongoing tasks are the test of the imaging algorithms and the quantitative comparison with simulations. Further experiments will be performed at proton accelerators.

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(14:45) M19-4, Total Least Squares with Spatial Constraint for Parametric Image Construction Using Multilinear Simplified Reference Tissue Model S. Seo1,2, D. S. Lee2, J. S. Lee1,2 1 2

Dept. of Brain and Cognitive Sciences, Seoul National University, Seoul, South Korea Dept. of Nuclear Medicine, Seoul National University College of Medicine, Seoul, South Korea

In parametric imaging of reversible tracer bindings, a multilinear simplified reference tissue model (SRTM) is more attractive than the original SRTM that has been widely used but usually depended on nonlinear fitting. Linear least squares (LLS), however, may lead to negatively biased estimates due to noisy independent variable in that model. We thus developed a new method using an extension of total least squares (TLS) that allows noises in some of independent variables and consequently avoids the bias appearing in LLS results. To overcome instability in TLS-based parametric imaging, initial estimates were further regularized with spatial constraint that restricts the resulting estimates to be similar to neighboring voxel values. The proposed method was evaluated using human dynamic [11C]RAC PET data (n=13). From both striatal ROI and voxel data, the distribution volume ratios (DVRs) were estimated by LLS and TLS-based methods while using the cerebellum as a reference region; then, the results of each method were compared with ground truth obtained by nonlinear fitting. The ROI DVRs from the proposed method were almost identical to the ground truth, whereas the LLS results were underestimated slightly. For the DVR images, LLS led to increased bias when compared to ROI results, but the proposed method resulted in comparable image quality without loss of accuracy. To conclude, in parametric imaging with multilinear SRTM, the proposed technique can provide accurate estimation by considering the noise in independent variables and also achieve good image quality by regularizing variability with spatial information. (15:00) M19-5, Simultaneous Reconstruction of the Activity Image and Registration of the CT Image in TOF-PET A. Rezaei, J. Nuyts Nuclear Medicine, UZ, Medical Imaging Research Center, B-3000 Leuven, Belgium

Previously, maximum-likelihood methods have been proposed to jointly estimate the activity image and the attenuation image (or the attenuation sinogram) from TOF-PET data. In this contribution, we propose a method that addresses the same problem for TOF-PET/CT by combining reconstruction and registration. The method, called MLRR, iteratively reconstructs the activity image while registering the available CT-based attenuation image, so that the pair of activity and attenuation maximizes the likelihood of the TOF emission sinogram. The algorithm is evaluated on 2D and 3D simulations and on a clinical data set. (15:15) M19-6, Accelerating Ordered Subsets with Relaxed Momentum for X-Ray CT Image Reconstruction D. Kim, J. A. Fessler Dept. of Electrical Engineering and Compputer Science, University of Michigan, Ann Arbor, MI, USA

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Recently, we have proposed combining ordered subsets (OS) methods and momentum technique for accelerated X-ray CT image reconstruction. We have observed rapid convergence speed in our experiments, but sometimes encountered instability. Here we introduce a diminishing step size rule to stabilize the algorithm, while preserving the fast convergence rate. (15:30) M19-7, Variational Noise Reduction for Spectral CT: Insights from the Perspective of Multiresolution Image Fusion D. S. Rigie, P. J. La Riviere Department of Medical Physics, University of Chicago, Chicago, IL, United States

In a recent paper, Leng et al. applied the HYPR-LR algorithm to photon counting CT data. The goal was to use the relatively low-noise, composite image constructed from all of the detected photons to reduce the noise in the images reconstructed from the various spectral bins. We show in this abstract that the HYPR-LR algorithm belongs to a class of pan-sharpening algorithms used in remote sensing. Motivated by this, we investigate the application of a more recent, variational pansharpening algorithm for denoising spectral CT data, highlighting a case that seems to challenge the HYPR-LR approach. (15:45) M19-8, Rigid Motion Compensation in Helical X-Ray CT J.-H. Kim1, J. Nuyts2,3, Z. Kuncic4, R. Fulton1,4,5,6 1

Discipline of Medical Radiation Sciences, University of Sydney, Sydney, NSW, Australia Department of Nuclear Medicine, Katholieke Universiteit, Leuven, Belgium 3 Medical Imaging Research Center, Katholieke Universiteit, Leuven, Belgium 4 School of Physics, University of Sydney, Sydney, NSW, Australia 5 Brain and Mind Research Institute, University of Sydney, Sydney, NSW, Australia 6 Department of Medical Physics, Westmead Hospital, Westmead, NSW, Australia 2

Patient motion is a major cause of artifacts in clinical X-ray CT. Several methods of retrospective rigid motion compensation in helical CT have been proposed, often limited to in-plane motion. Effective methods for head motion compensation exist for other imaging modalities such as PET and SPECT, which are able to correct for arbitrary rigid motion measured using an external motion-tracking device. We have previously shown the feasibility of compensating for known motion in helical CT simulations using a fully 3D iterative reconstruction algorithm called maximum likelihood transmission reconstruction (MLTR), given accurate motion estimates. Here we demonstrate the feasibility of effective rigid motion compensation in actual helical CT scans of a 3D Hoffman brain phantom. Reference (stationary) and motion scans were acquired while the phantom was tracked by an optical tracking system. As in the simulations, motion correction was achieved by spatially transforming the projections to compensate for the measured motion, which restored projection consistency, and performing fully 3D reconstruction with MLTR. Motion corrected and reference images were compared using mean squared error (MSE), correlation coefficient (CC) and a structural similarity index measure (SSIM). The effect of tracker sampling rate on correction accuracy was investigated by down-sampling the acquired tracker data. Accurate motion correction was achieved for sampling rates > 20Hz. We also applied a range of temporal shifts to the motion tracker measurements to determine the study-specific optimal synchronization offset. With 60Hz sampling and a 0.24 ms temporal offset the motion corrected 700

image was found to have a CC of 0.969 and a SSIM of 0.985 compared to the reference scan. We conclude that it is feasible to compensate for rigid motion in helical CT. The method may for example enable paediatric CT scans to be performed without the need for anesthesia/sedation.

***************** M20 (8)******************************* M20 Other Imaging Technologies II Friday, Nov. 1 14:00-16:00 GBR 103 Session Chair: Katsuyuki Taguchi, Johns Hopkins University, United States; Ho Kyung Kim, Pusan National University, South Korea

(14:00) M20-1, K-Edge Imaging with a Photon Counting CT System M. Matsumoto, F. Kaibuki, K. Ogawa Graduate School of Engineering, Hosei University, Tokyo, Japan

The purpose of our research is to measure the amount of contrast agents used in x-ray CT accurately. The use of contrast agents such as gold nano-particles enables molecular imaging with the x-ray CT system. To realize an energy discriminating measurement, we have developed a photon counting detector with a CdTe semiconductor that was able to measure x-rays with the count rate of 107 cps/mm2 with four energy windows. In order to measure the concentration ratio of the contrast agent, we used a k-edge imaging technique. The materials used in this experiment were Au-colloid, Pt-colloid and gadolinium solution. The results of experiments showed linearity between the linear attenuation coefficients of k-edge images that were calculated using the two energy bins near each k-edge, and the concentration ratios of the contrast agents. The accuracy of the measurement was strongly dependent on the calibration of the detector. (14:15) M20-2, Compensation for Spectral Distortions Due to Spectral Response and Pulse Pileup Effects for Photon Counting CT K. Taguchi1, K. Nakada2, K. Amaya2 1 2

Radiology, Johns Hopkins University, Baltimore, MD, U.S.A. School of Information Science and Engineering, Tokyo Institute of Technology, Tokyo, Japan

Energy sensitive photon counting detector-based x-ray computed tomography (PCD-CT) has shown promises to provide various clinical benefits such as enhanced tissue contrast, decreased image noise, decreased radiation dose to patients, and more accurate material decomposition. Major technical challenges include PCD's non-ideal performances such as a loss of counts and distorted spectrum due to "spectral response effects (SRE)" and pulse pileup effects (PPE). The former occurs at any count-rates (or the intensity of x-rays) and includes charge sharing, K-escape 701

x-ray, and Compton scattering. The latter is caused by quasi-coincident photons incident onto the detector and becomes severe when count-rates are high. When left uncorrected, these two effects will result in biases and artifacts in images; thus, they are the major roadblock on the way to clinical PCD-CT systems. Many studies use too simplistic and inaccurate PCD models, i.e., either paralyzable or nonparalyzable detector with a fixed deadtime. In fact, most of PCDs is a pulse height analyzer (PHA), and multiple energy thresholds of PHA will act as independent paralyzable detectors with no fixed deadtime. Our recent study on pulse pileup statistics showed that counts recorded by PHA are not Poisson distributed. In this work, we propose a method to compensate for both SRE and PPE which uses multivariate normal (MVN) distributions. The basic systematic evaluation showed the MVN model decreases noise better than Poisson model does when a descent amount of PPE is present. The synthesized patient study confirmed that the proposed method can not only overcome spectral distortions due to SRE and PPE but also decrease the image noise compared to the current energy-integrating detector-based EID-CT. PCD-CT with the proposed method may enable a dose reduction of as much as 57% (1/1.77x100%) from EID-CT. (14:30) M20-3, Joint Estimation of Tissue Types and Linear Attenuation Coefficients for Photon Counting CT K. Nakada1, K. Amaya1, K. Taguchi2, G. S. K. Fung2 1 2

School of Information Science and Engineering, Tokyo Institute of Technology, Meguro, Tokyo, JAPAN School of Medicine, Johns Hopkins University, Baltimore, MD, U.S.A.

Energy sensitive photon counting detector-based x-ray computed tomography (PCD-CT) has been one of the hottest research topics latelys, as it is expected to provide various clinical benefits including more accurate material decomposition. It can allow software applications to, e.g., separate blood vessels from bones, quantify the fat mass, etc. The typical approach to process PCD data consists of the following two steps. First, by applying material decomposition, density images of basis functions (discussed later), w, are reconstructed from spectral projections. Second, images of linear attenuation coefficients and tissue types are estimated from w. This sequential method decouples the two steps and makes it difficult to use a priori information on tissue types such as follows to accurately estimate linear attenuation coefficients and tissue types. For example, The values of neighboring pixels of linear attenuation coefficients (and w) are expected to vary smoothly and continuously if they belong to the same tissue types, while they may be discontinuous at organ boundaries. The typical values of the chemical composition and mass density of various human tissue types or organs are provided. In this paper, we propose a new framework to jointly estimate images of the energy-dependent linear attenuation coefficients and tissue types from PCD data. Our algorithm employs maximum a posteriori (MAP) Bayesian estimation based on pixel-based latent variables for tissue types: Poisson likelihood models PCD data; a Markov random field (MRF) represents the geometrical a priori information on tissue types and w; and the statistical a priori information relates tissue types and w. We performed a computer simulation to evaluate the effectiveness of the proposed method compared with the sequential, two-step method. (14:45) M20-4, Spectral CT Imaging with Hybrid Detectors in Integrating and DynamicThreshold Counting Modes 702

L. Li, J. Chu, Z. Chen, W. Cong, G. Wang Department of Engineering Physics,Tsinghua University, Beijing, China

In recent years, spectral CT with photon counting detectors (PCDs) has exhibited more advantages compared to conventional CT systems. Spectral CT has the potential to substantially advance CT imaging by reducing image noise and dose, improving contrast and target specificity, and enabling functional imaging with special molecular markers (e.g. Gold nanoparticles). The current PCDs, however, is difficult to balance the amount of energy bins and the data noise of statistical fluctuation at each bins. More energy bins mean higher energy discriminating ability, but lower photon number at each bin. Moreover, in order to obtain enough energy bins, the current PCD is made up by small spectral detector subelements which have different thresholds. However, the more energy bins it has, the more complicated circuitry is. Hence, the PCD element becomes complex and large if we want many energy bins. Both spatial and energy resolutions are compromised. The state-of-the-art PCD has eight energy bins. It is difficult to make more energy bins. The overall goal of our research is to develop a hybrid detector which combines the integrating and dynamic-threshold counting modes. Its energy thresholds, or energy bins, can be flexibly arranged and dynamically changed during the spectral CT scanning. In each energy bin, current-integrating readouts are used. Thus, we can get many energy bins with very limited amount of PCD subelements. We develop a smart algorithm to reconstruct the true-color CT images by the data from this hybrid detector with adjustable energy thresholds (e.g. randomly changing). This paper will introduce this new spectral CT system with hybrid detector, its image reconstruction algorithm, and the simulation results. (15:00) M20-5, Novel Results from a First Preclinical X-Ray Phase-Contrast CT Scanner A. Velroyen1, A. Tapfer1, A. Yaroshenko1, M. Bech1,2, M. Mueller1, B. Pauwels3, J. Hostens3, P. Bruyndonckx3, X. Liu3, A. Sasov3, F. Pfeiffer1 1

Department of Physics and Institute of Medical Engineering (IMETUM), Technische Universitaet Muenchen, Munich, Germany 2 Medical Radiation Physics, Lund University, Lund, Sweden 3 Bruker MicroCT, Kontich, Belgium

Dark-field and phase-contrast imaging, which generate contrast from ultra-small angle scattering and refraction of x-rays in matter, have been shown to increase soft-tissue contrast and provide complementary information to conventional attenuation-based x-ray imaging [1,2], thus great potential for medical imaging is anticipated. As a step towards clinical implementation, we have developed a first grating-based preclinical phase-contrast CT scanner with a three-grating interferometer installed on a rotating gantry [3, 4]. To extract the complementary contrast modes, the interferometer is used to transfer sample-induced minute directional changes of the x-rays into intensity variations on the detector. Slight instabilities in the precise alignment and relative movement of the gratings translate into image artifacts. Therefore, we analyzed thermal and rotation-induced effects on the stability of phase extraction during a tomographic acquisition. Newly developed software tools are presented that allow regaining accurate images despite those instabilities. Moreover, upgrades of scanner hardware are shown that improve visibility and mechanical stability in general. With respect to imaging, CT scans of several biological samples and phantoms clearly demonstrate the improved soft-tissue contrast and the obtained complementary information in comparison to conventional attenuation-based imaging. 703

Furthermore, first planar radiographic images of a living mouse in differential phase, dark-field and attenuation contrast are presented, as well as phase-contrast ex-vivo mouse CT images made possible by the software and hardware improvements introduced to the scanner. By proving the feasibility of phase-sensitive imaging with a compact rotating gantry, this work represents an important milestone in translating phase-contrast from bench to bedside. [1] Pfeiffer et al. Nat Phys 2006, [2] Pfeiffer et al. Nat Mater 2008, [3] Tapfer et al. PNAS 2012, [4] Tapfer et al. Med Phys 2011 (15:15) M20-6, Quantitative Tissue Characterization Using Grating-Based X-Ray PhaseContrast Imaging M. Willner1, J. Herzen1,2, M. Viermetz1, M. Marschner1, G. Fior1, A. Hipp1,2, M. Chabior1, A. Fingerle3, P. Noel3, C. Braun4, F. Fischer4, F. Pfeiffer 1

Department of Physics & Institute for Medical Engineering, Technische Universitaet Muenchen, Garching, Germany 2 Institute of Materials Science, Helmholtz-Zentrum Geesthacht, Geesthacht, Germany 3 Department of Radiology, Technische Universitaet Muenchen, Muenchen, Germany 4 Institute of Forensic Medicine, Ludwig-Maximilian-Universitaet, Muenchen, Germany

Starting in the 90s, many efforts have been made to exploit the phase shift that X-rays undergo when traversing an object. Especially the visualization of weakly absorbing materials profits from the high sensitivity that can be achieved with this contrast modality. Ten years ago, X-ray grating interferometry has been added to the portfolio of phase-contrast CT imaging techniques at synchrotron radiation facilities. The method has been successfully adapted to operate with laboratory X-ray sources shortly after and allows for quantitative determination of the electron density distribution within an object. Conventional attenuation based images are acquired simultaneously and co-registered. If attenuation is not solely based on Compton scattering, phase contrast and attenuation contrast yield complementary information on the tissues present in the sample. Here, we examine the potential of grating-based phase-contrast imaging for quantitative tissue characterization by the combination of both contrast modalities. A Talbot-Lau interferometer has been employed with a rotating-anode X-ray tube and a photon-counting detector to image various types of soft tissue. The samples were placed in a phosphate buffered solution (PBS) and cooled down to a temperature of 4C during the measurements. The tomographic reconstructions were quantitatively analysed and the results were related to theoretical values obtained from elemental tissue compositions available in literature. Based on further theoretical considerations, we discuss the possibility to assign biological quantities like fat or protein content to the tissues. Our study demonstrates the opportunities for quantitative tissue characterization using grating-based phase-contrast imaging at laboratory X-ray tubes and serves as inspiration for the identification of new interesting applications of the technique in biomedical imaging. (15:30) M20-7, Evaluation of Grating-Based Phase-Contrast Tomography for Imaging of Human Soft Tissue Using Synchrotron and Conventional X-Ray Sources J. Herzen1,2, M. S. Willner2, A. Hipp1,2, P. B. Noel3, A. A. Fingerle3, H. Hetterich4, T. Saam4, S. Fill4, S. Grandl4, A. Sztrokay4, K. Hellerhoff4, D. Mayr5, F. Pfeiffer2 1 2

Institute of Materials Science, Helmholtz-Zentrum Geesthacht, Geesthacht, Germany Department of Physics & Institute for Medical Engineering, Technische Universitt Mnchen, Munich, Germany

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3

Department of Radiology, Technische Universitt Mnchen, Munich, Germany Department of Clinical Radiology, Ludwig-Maximilians-Universitt Mnchen, Munich, Germany 5 Department of Pathology, Ludwig-Maximilians-Universitt Mnchen, Munich, Germany 4

In the last few years, grating-based X-ray phase-contrast imaging has been demonstrated to enhance the contrast in weakly absorbing materials, as for example in biological soft tissue. Especially, its extendibility to conventional polychromatic X-ray sources leads to a broad use of this modality. With our work we aimed to evaluate the performance of the method in visualizing different human diseases ex vivo at different length scales: at high spatial resolution using highly brilliant synchrotron radiation sources, and at lower spatial resolution with a polychromatic X-ray source. Here, we will present our recent results on ex vivo carotid arteries, different types of human breast, and liver carcinoma. These tissues reveal only weak soft-tissue contrast in conventional CT. From the reconstructed slices tissue-specific attenuation coefficients and electron density distributions were determined. The tomographic slices were analyzed in terms of contrast-to-noise ratios and compared to histopathology or other gold standards. Our study shows that grating-based phase-contrast computed tomography significantly enhances the soft-tissue contrast in human ex vivo specimens at high and low spatial resolution. The phase-contrast signal allows clearly distinguishing between healthy and diseased tissue even in the low-resolution polychromatic measurements. The contrast improvement in the phase-contrast signal compared to the attenuation signal was reached without any use of contrast agents, which can have a substantial clinical impact. Our results provide initial evidence that grating-based phase contrast enables enhanced tumor detection in both, human breast and liver tissues. Tissue-specific values can be obtained for numerical simulations and optimization of the setup, as well as for designing dedicated phantoms. (15:45) M20-8, Many-View under-Sampling (MVUS) Technique for Low-Dose CT T. Lee, S. Abbas, S. Cho Korea Advanced Institute of Science and Technology, Daejeon, Korea

In computed tomography (CT), radiation dose delivered to the patient is one of the major concerns. Sparse-view CT is a viable option to low-dose CT. However, a fast power switching of an x-ray tube, which is needed for the sparse-view sampling, can be challenging in many CT systems. We have recently proposed a novel alternative approach to sparse-view CT that can be readily incorporated in the existing CT systems, and have successfully shown its feasibility. Instead of switching the x-ray tube power, one can place an oscillating multi-slit collimator between the x-ray tube and the patient to partially block the x-ray beam. In this paper, an experimental study is performed to evaluate the performance of the proposed CT scan scheme. Bench-top CT projection data of a CatPhan 600 phantom was acquired by use of the oscillating multi-slit collimator. For image reconstruction, we used a total-variation minimization (TV) algorithm which has shown its out-performance in many sparse-view CT applications.

**************** M21 (61) ****************************** M21 Imaging in Therapy / New Detector Materials and Technologies 705

Friday, Nov. 1 16:30-18:30 Hall B2 Session Chair: Yiping Shao, The University of Texas M.D. Anderson Cancer Center, United States; Stan Majewski, West Virginia University, United States

M21-1, Preliminary Results of an in-Beam PET Prototype for Carbon Therapy H.-I. Kim1,2, S. J. An1,2, C. Y. Lee1,2, W. J. Jo1,2, E. Min3, K. Lee3, Y. Kim4, J. Jeong4, Y. H. Chung1,2 1

Department of Radiological Science, College of Health Science, Yonsei University, Wonju, Korea Institute of Health Science, Yonsei University, Wonju, Korea 3 Department of Radiologic Science, Korea University, Seoul, Korea 4 Nucare Medical Systems, Inc, Incheon, Korea 2

PET scanners can be utilized to verify dose distributions of the therapeutic hadron beams. The purpose of this study is to develop a dedicated in-beam PET scanner for monitoring patient dose in carbon beam therapy and to evaluate its feasibility. The scanner consists of 14 detector modules with a 30.2 cm inner diameter for brain imaging. Each detector module is composed of a 9 x 9 array of 4.0 mm x 4.0 mm x 20.0 mm LYSO crystals, laser-cut reflector grids and four roundshape PMTs for photomultiplier-quadrant-sharing (PQS) technology. PMT signals from each module are acquired through a dedicated electronic board that performs signal amplification and baseline restoration. Field-programmable gate array (FPGA) combined 64-channel data acquisition board was used for digitization and signal processing such as position calculation, energy discrimination and timing stamping. An expectation maximization algorithm was used for image reconstruction. To characterize PET prototype, the detection efficiency and the spatial resolution were measured using a point-like FDG source. The experimental results agreed well with simulations. M21-2, Prompt Gamma Imaging of a Proton Pencil Beam at Clinical Current Intensities: First Test on a Prototype and Development of a Full-Size Camera I. Perali1,2, A. Celani3, E. Baio1, C. Fiorini1,2, T. Frizzi3, E. Clementel4, S. Henrotin5, G. Janssens5, D. Prieels5, F. Roellinghoff5, J. Smeets5, F. Stichelbaut5 1

Elettronica, Informazione e Biooingegnera, Politecnico di Milano, Milan, Italy Sezione di Milano, Istituto Nazionale Fisica Nucleare, Milan, Italy 3 XGLab, Milan, Italy 4 Universit catholique de Louvain, Louvain-la-Neuve, Belgium 5 Ion Beam Applicaitons, Louvain-la-Neuve, Belgium 2

Treatments delivered by proton therapy are affected by uncertainties on the range of the beam within the patient. To reduce these margins and improve feedback on treatment delivery, different projects are investigating real-time range control by imaging prompt gammas emitted along the proton tracks in the patient. This study supports the development of a prompt gamma camera using a knife-edge slit collimator to produce a reversed 1-dimensional projection of the beam path on a scintillation detector for treatments delivered in pencil beam scanning mode. The ability of this camera design to detect modifications of the beam penetration depth in a PMMA target was already demonstrated down to 1 mm accuracy for doses compatible with single pencil beams at 706

low proton beam currents thanks to the HiCam photodetection system. In order to fulfill the very demanding count rate capability required for prompt gamma imaging at clinical beam currents, a new, dedicated, cost-effective photodetection system was designed and will be presented, as well as experimental results. This ultra-fast, 1-dimensional, high-energy gamma imaging device relies on two rows of 20 LYSO crystal slabs, directly coupled to SiPMs arrays and readout by 40 independent acquisition channels in fast counting mode. A test board limited to 2 channels was implemented to benchmark the performances of various components and validate the adequate combination of crystal material, surface treatment, optical coupling and SiPMs. This prototype was tested during proton irradiation at the West German Proton Therapy Centre in Essen and was, to our knowledge, the very first to achieve successful acquisitions at clinical beam currents of several nA at nozzle exit. These performances were furthermore demonstrated in challenging conditions up to the maximum clinical beam energy of 230 MeV, laying a major milestone towards the development of a practical solution for online range control in proton therapy. M21-3, The Application of the Axial PET Concept to Novel Imaging Scenarios P. Solevi1, I. Torres-Espallardo1, J. Gillam1, J. Cabello2, J. Oliver1, M. Rafecas1 1 2

IFIC (CSIC/Universidad de Valencia), Valencia, Spain Klinikum rechts der Isar der Technischen Universitat Munchen, Munich, Germany

AX-PET is a Positron Emission Tomography (PET) device based on a novel geometrical concept. The axially oriented crystals are interleaved with Wavelength Shifter arrays in order to recover the longitudinal coordinate. AX-PET provides a high sensitivity due to its layered geometry that yields a large event recovery, so that events such as Inter-Crystal Scatter can be included in the reconstruction process without any resolution loss in the final image, these events constituting 20% of the total detected ones. Additionally, the AX-PET geometry is flexible and easily scalable to fulfil more strict constraints imposed by different medical applications. These reasons lead us to explore the potential of AX-PET in novel imaging scenarios such as hadrontherapy monitoring. The need to survey the ion treatment to assure a proper dose delivery to the target tumour is an important issue that poses specific requirements in terms of spatial resolution and sensitivity. We present the results of a full ring AX-PET scanner monitoring in-room monoenergetic proton and Carbon ion beams at different energies delivered to a PMMA phantom. Additionally a more realistic Treatment Plan was simulated in order to investigate more complex sources. AX-PET was tested with Digital Silicon Photomultipliers providing a better timing performance, achieving a coincidence time resolution of 269 s (FWHM). We will present the previous images including the Time Of Flight information in the reconstruction process. M21-4, Proton Beam Range Verification Using off-Site PET by Imaging Novel Proton-Activated Fiducials J. Cho1, G. S. Ibbott1, R. Amos1, M. Kerr1, O. R. Mawlawi2 1 2

Radiation Physics, MD Anderson Cancer Center, Houston , TX, USA Imaging Physics, MD Anderson Cancer Center, Houston, TX, USA

Purpose: Previously we showed that when Zn68 and Cu63 fiducials are placed along the distal end of the proton beam range, they result in higher PET signals than surrounding material such as 707

Plastic Water and balsa wood following proton treatment. In this work we investigate the use of PET signals from activated Zn68 and Cu63 fiducials for accurate proton range verification in a pseudo realistic clinical setting. Methods: Zn68 (>97%) and Cu63 (>69%) foils (10 x 10 mm) of different thicknesses (0.1, 0.25, and 0.5 mm) were imbedded at different depths in a rectangular block of raw beef (12 x 16 x 5 cm) that was used to represent patient soft tissue. The phantom was irradiated by a 160 MeV, 10-cm SOBP proton beam with 5 Gy and PET scanned for 5 hr after a delay of 36 min. Images were reconstructed at 30 min intervals (typical duration of a PET scan) without decay correction and were compared to determine the image with the best visibility of activated foils. Treatment planned isodose lines of the phantom were overlaid on top of foil locations to determine the minimum isodose line level that corresponds to activated foils. Results: The best visibility of a 30 min PET scan was obtained after 2 hr 6 min delay. Visibility increased with foil volume and scan time post irradiation until 2 hours before it decreased due to a decrease in accumulated coincidence events. Zn68 foils located at greater than 50% isodose line were activated while Cu63 foils located at greater than 95% isodose line were activated. Foils located beyond those isodose lines were not activated. In both cases, foils of > 25 mm3 were clearly visible. Conclusions: Activation of Zn68 and Cu63 foils and their correspondence with isodose lines suggest the possibility of using the implanted fiducials for proton range verification. M21-5, A new beam range monitoring method by measuring low energy photons M. Yamaguchi1, K. Torikai2, N. Kawachi3, H. Shimada2, T. Satoh1, Y. Nagao1, S. Fujimaki3, M. Kokubun4, S. Watanabe4, T. Takahashi4, K. Arakawa1,2, T. Kamiya1, T. Nakano2 1

Takasaki Advanced Radiation Research Institute, Japan Atomic Energy Agency, Takasaki, Gunma, Japan Heavy Ion Medical Center, Gunma University, Maebashi, Gunma, Japan 3 Quantum Beam Science Directorate, Japan Atomic Energy Agency, Takasaki, Gunma, Japan 4 Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Kanagawa, Japan 2

To improve confidence in particle beam therapy, range monitoring techniques are of major importance for the medical field. In this work, we have studied about a new method for monitoring the beam range in heavy-ion radiation therapy by measuring low energy photons emitted from the track of the ion beam. An experimental study was performed by use of Heavy Ion Medical Accelerator in Chiba (HIMAC). A carbon-12 beam having the energy of 290 MeV/u and intensity of 50 million particle par second was delivered to an experimental room and injected into a cylindrical water phantom. A CdTe semiconductor detector was placed at the same height as the beam line. A lead slit-type collimator, having an aperture of 2 mm and a thickness of 10 cm, is placed in front of the detector to restrict the direction of the detected photons. In order to measure the position dependence of the low energy photon count, the range position was varied by changing the injection energy. The injection energy was varied by a binary energy degrader placed about 100 cm upstream of the beam focal point. The number of photons detected in the energy range from 63 to 68 keV. We found that the measured photon count decreases when the position gets close to the range and the derivative of the photon count clearly changes at -6 mm in front of the range position. We have tried to explain the sudden change of the derivative of photon count by assuming that the main component of the photons occurs from secondary electron bremsstrahlung (SEB) and found that the derivative of the generated bremsstrahlung curve suddenly changes at -2.7 mm; it is slightly larger than the experimental value of -6 mm. These results indicate that this new method could deduce the range position from the observation of bremsstrahlung to an accuracy of a few mm. 708

M21-6, In-Situ PET Imaging with Digital SiPMs for Proton Range Verification: Initial Performance Study P. Cambraia Lopes1,2,3, I. Rinaldi4, J. Bauer4, S. Brons2, P. Dendooven5, J. Huizenga1, P. Crespo3,6, K. Parodi4,7, D. R. Schaart1 1

TNW/RST/RIH, Delft University of Technology, Delft, The Netherlands Heidelberg Ion-Beam Therapy Center, University Clinic of Heidelberg, Heidelberg, Germany 3 LIP-Coimbra, Laboratório de Instrumentação e Física Experimental de Partículas, Coimbra, Portugal 4 Department of Radiation Oncology, Heidelberg University Clinic, Heidelberg, Germany 5 Kernfysisch Versneller Instituut, University of Groningen, Groningen, The Netherlands 6 Physics Department, Universidade de Coimbra, Coimbra, Portugal 7 Department of Medical Physics, Ludwig Maximilian University, Munich, Germany 2

At present, positron emission tomography (PET) is the only imaging modality clinically tested for treatment monitoring during or short after treatment in particle therapy (PT). Optimal use of PET imaging requires in-situ acquisition of the 15O signal due to the relatively high abundance of oxygen in biological tissues and its relatively short half-life of ~ 2 min, enabling shorter scan times which are less sensitive to biological washout. In this work we present an initial performance test of PET modules, manufactured by Philips Digital Photon Counting (PDPC). The modules consist of 2x2 DPC3200-22-44 arrays of digital silicon photomultipliers (dSiPMs) and pixelated crystal arrays of LYSO:Ce. A proof-of-concept in-situ PET setup, comprising two dSiPM modules operating in coincidence, was tested at a clinical proton beam with an energy of 125.67 MeV and an intensity of 1.2⋅109 protons/s. The proton-induced activity inside homogenous PMMA and PE phantoms was acquired in-situ during 2.5 min long irradiations as well as during a period of at least 15 min after irradiation. Coincidence data covering the whole proton range in both phantoms was acquired. Furthermore, the sensitivity of the PET setup to detect variations of the proton range in PMMA was characterized. Based on a preliminary image reconstruction, it was found that Bragg peak shifts as small as 1 mm can be detected by visual inspection of the images. An accurate quantification of activity fall-off estimation for different acquisition time-windows will be presented at the conference. M21-7, 4D and Multi-Phase Breath-Hold CT Imaging with Synchronized Intravenous Contrast Injection for Liver Tumor Delineation S. Beddar1, Y. Suh1, Z. Wen1, P. Das2, M. E. Delclos2, S. Krishnan2, B. Minsky2, C. H. Crane2 1 2

Department of Radiation Physics, University of Texas, MD Anderson Cancer Center, Houston, TX, USA Department of Radiation Oncology, University of Texas, MD Anderson Cancer Center, Houston, TX, USA

In order to better visualize and delineate certain liver tumors on 4D or breath-hold CT scans, synchronized intravenous (IV) contrast injection is used at our institution. The purpose of this study is to present these two tumor management techniques used for tumor delineation and treatment delivery strategy. 4DCT imaging is performed while the IV contrast is synchronized with image acquisition over the regions of interest. Image acquisition is timed with either the portal venous phase, 45 s after the initiation of contrast injection, or the delayed phase, 270 s after the initiation of contrast injection. Multi-phase breath-hold CT imaging consists of three to five breath-hold CT scans acquired one after another throughout the portal venous and washout phase. To maintain the consistent breath-hold level between breath-hold scans, visual feedback is provided to the patient via goggles, so that the patient can view his/her breathing traces and 709

breath-hold levels. More than 100 patients have been scanned for the last two years. Liver tumors appear hypodense compared with the normal liver parenchyma due to washout of the contrast from the tumor. The increase in the contrast differential between tumors and normal liver objectively improves tumor visibility and delineation, clarifying the tumor borders and allowing clearer definition of the nearby vessels. In the worst case, multi-phase breath-hold CT imaging provides us at least one good contrast-enhanced CT dataset for tumor delineation. Whereas, with 4DCT, there are rare instances where we miss the contrast differential between tumors and normal liver. Both techniques of 4D and multi-phase breath-hold CT imaging with synchronized IV contrast injection have been successfully used for a large population of patients with liver tumors undergoing radiation therapy treatment. Our experiences using these techniques will be highlighted, in conjunction with the use of new respiratory motion management technologies and concepts. M21-8, To Use or Not to Use SiPM Based in-Beam PET for Proton Therapy: Ramification of Neutron Radiations to the Imaging Performance and Abatement Methods X. Sun1, X. R. Zhu2, K. Lou1, Y. Shao1 1 2

Imaging Physics, UT MD Anderson Cancer Center, Houston, TX, United States Radiation Physics, UT MD Anderson Cancer Center, Houston, TX, United States

A critical issue for using in-beam PET to improve beam-range verification in proton therapy is the concern of neutron exposure and performance degradation of the detector and electronics, in particular if silicon photomultiplier (SiPM) is used, and the consequences to the overall PET imaging performance. While radiation hardening electronics has been well investigated and can be designed and implemented at the normal therapy radiation environment, there are many unknowns about the impact of neutron radiations to the detectors and corresponding strategy for remedy which is the objective of this study. Individual LYSO scintillators and assembled detectors from LYSO and SiPM arrays (Hamamatsu MPPC S11829-3344MF) were irradiated by neutrons generated from 200 MeV proton interactions with beam line and a brain size PMMA phantom, at the 47.4, 94.8, and 142.2 mSv/h dose levels, corresponding to 40, 80 and 120 normal proton therapies. Amplification gain and dark current of SiPM arrays were measured before and after the irradiations, so as the detector module performance. Results show that neutron radiations caused: no LYSO light output change; slight SiPM gain drops (~6% at 142.2mSv/h dose), but relatively big increase of dark current (0.95uA per mSv/h neutron dose summed over all 16 channels). Attributed from our fast trigger and charge integration ASIC readout electronics, there were negligible changes of timing and energy resolutions, crystal map, and DOI measured beyond statistical variations. There is minor photo-peak shifting (~6%) at 142.2 mSv/h dose level due to SiPM gain reduction, which can be corrected by post-data processing. Conclusion: up to 120 routine proton therapies, the performance of MPPC based detector module was not affected by the neutron radiations after a simple energy correction. The accumulated neutron dose impact has been studied through annealing and correction to electronics baseline shifting, which will be also reported at the conference. M21-9, CBCT Image Reconstruction of a Moving Target with an on-Board Imaging System for Radiation Therapy K. Usui1,2, S. Kabuki3, C. Kurokawa1, S. Sugimoto1, K. Sasai1, E. Kunieda3, K. Ogawa2

710

1

Department of radiology, Juntendo University School of Medicine, Tokyo, Japan Graduate School of Engineering, Hosei University, Tokyo, Japan 3 Department of radiology, Tokai University School of Medicine, Kanagawa, Japan 2

To accomplish accurate irradiation to a target, image information about the target is very useful in radiotherapy. A kilo-voltage cone-beam computed tomography (kV-CBCT) system mounted on a linear accelerator can verify the accuracy of the set-up position and the size and location of the target on each treatment day. However, the gantry of the CBCT system is heavy and so requires a long data acquisition time. As a result, image distortion occurs in the case of a moving target. In this study, we proposed a method to reconstruct a target less affected by any motion of the target, and evaluated the proposed method with a moving phantom. In our method, CBCT images of the moving phantom were acquired, and the target position in two directions was detected with a template matching method using these projection images. And we selected data acquisition angles of the projection images in which the target is located in predefined regions in the projection images, and made a sinogram with the projection image of selected angles. A less blurred image was reconstructed with a filtered-backprojection method from the sinogram. The results of experiments showed that the blurring caused by the movement of the phantom was reduced with our proposed method. M21-10, Reconstruction of Implanted Marker Trajectory from Cone-Beam CT Projection Images Using an Inter-Dimensional Correlation Model B. Cho1, P. Poulsen2, P. Keall3 1

Radiation Oncology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea Radiation Oncology, Aarhus University Hospital, Aarhus, Denmark 3 Radiation Physics Laboratory, Sydney Medical School, University of Sydney, Sydney, Australia 2

CBCT takes a key role in image-guided radiation therapy for accurate alignment of tumor to radiation beam. Advanced radiation therapy demands real-time motion management for precise delivery of radiation dose. The purpose of this study is to develop a new position estimation method for implanted gold markers using sequential kV projection images acquired for CBCT, and investigate the performance through a simulation study. To estimate the 3D motion trajectory of respiratory-induced motion from CBCT projection images, we utilized an inter-dimensional correlation between each direction of respiratory-induced target motion. Especially since SI motion is always resolved on the projection images due to axial rotation of CBCT acquisition, we tried to link SI motion to the other dimensions: LR(t) =a_LRSI(t)+b_LR, AP(t)=a_APSI(t)+b_AP. The model parameters were determined with least-squares estimation by minimizing the discrepancy between the measured and model-estimated positions projected on the imager. The performance of the proposed method was assessed by simulating CBCT acquisition for a 160 thoracic/abdominal tumor trajectories from 42 patients by a Cyberknife Synchrony system. Each trajectory was divided into one-minute segments for CBCT simulation and the total number was 5,113. To simulate CBCT acquisition, the tumor positions of each trajectory segment was projected onto a flat panel detector with imaging frequency of 10 Hz, resulting in 600 projections per scan. The mean rms errors were 0.21, 0.24, 0.006 mm in the LR, AP, SI direction, respectively, while the maximum rms errors for any trajectory were 3.96, 2.46, 0.22 mm, respectively. Most tumor trajectories were well estimated. 3D rms error of the estimated trajectory was less than 1 mm and 2 mm for 94.8% and 99.0%, respectively. In conclusion, since respiratory motion is fairly periodic and inter-correlated as well, the proposed method can be effectively 711

applied to estimate tumor motion. M21-11, Compton Imaging in a High Energetic Photon Field T. Kormoll1, D. Bemmerer2, F. Fiedler2, C. Golnik1, F. Hueso Gonzalez1, K. Heidel2, M. Kempe2, H. Rohling1, K. Schmidt2, S. Schoene2, L. Wagner2, G. Pausch1 1 2

OncoRay, University of Technology Dresden, Dresden, Germany Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany

Through the well defined range of charged particles in matter, cancer irradiation by means of ions can be very tumor conformal. However, external range verification is needed to fully exploit the advantages of ion beam therapy. Nuclear interactions between the projectiles and targets result in excited nuclei which emit photons in the MeV energy range during deexcitation. With a Compton camera, it should be possible to image the origin of these photons which is correlated to the beam position. A prototype Compton camera comprising CdZnTe layers and scintillation detectors has been developed and tested with nuclear point sources. In this work, the performance of the camera is tested at a tandetron beam line in a clean radiation field of 4.44 MeV photons. It is investigated if Compton imaging in this energy regime is feasible. M21-12, Current Status of 4D Offline PET-Based Treatment Verification at the Heidelberg IonBeam Therapy Center C. Kurz1, J. Bauer1, D. Unholtz1, S. Combs1, J. Debus1, D. Richter2, R. Kaderka2, C. Bert2,3, K. Stuetzer4, C. Gianoli1,5, G. Baroni5, K. Parodi6 1

Heidelberg Ion-Beam Therapy Center and Department of Radiation Oncology, Heidelberg University Hospital, Heidelberg, Germany 2 GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt, Germany 3 Strahlenklinik, University Clinic Erlangen, Erlangen, Germany 4 OncoRay - National Center for Radiation Research in Oncology, Technische Universitaet Dresden, Dresden, Germany 5 Department of Electronics Information and Bioengineering, Politecnico di Milano, Milano, Italy 6 Department of Experimental Physics - Medical Physics, Ludwig-Maximilian-University, Munich, Germany

At the Heidelberg Ion-Beam Therapy Center, patient treatment is monitored offline by comparing the irradiation-induced β+-activity, measured by a commercial full-ring PET/CT scanner installed next to the treatment site, with a corresponding Monte-Carlo (MC) simulation based on the planned treatment. While the usefulness of 3D offline PET-based treatment verification has already been shown, the feasibility of 4D offline PET-based treatment monitoring, accounting for the tumour motion during the irradiation and the subsequent PET acquisition, still needs to be demonstrated. In this work, PMMA phantoms of different geometries were irradiated once under stationary and once under moving conditions. In the latter case, a pressure sensor motion surrogate was used to monitor the rigid target movement during the gated ion-beam application and the following PET acquisition. In the same way, respiratory motion was monitored during the irradiation and subsequent PET/CT scans of several patients with respiratory motion affected target volumes in the liver. In all cases, the knowledge or estimation (from 4D CT) of the target trajectory enabled a 4D analysis of the ion-beam delivery and the post-irradiation PET. The reconstructed 4D PET data were compared to the stationary reference (phantom study only) and to the results of a dedicated 4D MC simulation framework. In the simplified scenario of high dose 712

irradiations of moving phantoms, results comparable to the static reference measurements could be obtained by using the available gated 4D PET reconstruction. However, time-resolved analysis of the clinical data was found to suffer from the very low counting statistics, hindering a reliable verification of the applied treatment under consideration of the tumour motion. Still, in the case of small respiratory motion amplitudes (below 1cm), therapy application could be verified by comparing the 3D reconstructed PET data to a 3D MC prediction. M21-13, Accuracy Improvement of Time Delay Correction Method for PET-Based Tumor Tracking T. Shinaji1,2, H. Tashima2, E. Yoshida2, T. Yamaya2,3, H. Haneishi3 1

Graduate School of Engineering, Chiba University, Chiab, Japan Molecular Imaging Center, National Institute of Radiological Sciences, Chiba, Japan 3 Research Center for Frontier Medical Engineering, Chiba University, Chiab, Japan 2

The worlds first open type PET, named OpenPET, is being developed at the National Institute Radiological Sciences. We are aiming to employ the OpenPET in radiotherapy and to track the respiratory motion of a tumor in the thoracoabdominal region of a patient. By using PET images, we expect that the tumor itself can be directly visualized without using radio-opaque markers. Our prototype OpenPET system can output reconstructed images at about 2 frames per second with about a 2 s delay; this delay is mainly due to the reconstruction calculation time. Therefore we presented a time delay correction method with belt type piezoelectric sensor for tumor tracking for the OpenPET with support vector regression method in the last IEEE NSS-MIC meeting. In this paper, we improved accuracy of this method. In the modified method, we added body surface displacement velocity as a secondary independent variable of the regression line so that it represents hysteresis effect. In addition, we restrained the signal distortion due to AC coupling system by unscented Kalman filter. As the result, the mean compensation error was decreased from 2.63 mm to 2.30 mm. We think that the accuracy can be further improved by optimizing those parameters in the unscented Kalman filter. M21-14, 2D Image Analysis Using Light Output of Scintillation Screen for Uniform Scanning Mode S. Cho, J.-I. Shin, S. Park, C. Jeong, J. H. Jeong, D. Shin, Y. K. Lim, J. Y. Kim, S. B. Lee Proton Therapy Center, National Cancer Center, Goyang-si, South Korea

Recently, we have developed proto-type CCD camera scintillation screen system which can measure dose distribution for various beam delivery mode in proton therapy. This system directly provides not only range distribution but also 2D dose distribution on the light output information. In this study, we analyzed 2D dose distribution of proton beam for uniform scanning mode using CCD camera - scintillation screen system. In this study, the light outputs from scintillation screen for uniform scanning mode were acquired by a CCD camera. At each measurement, the layer of range modulator was changed to the next step. First, we measured the scintillation output for SOBP beam (10 cm width, 15 g/cm2 range) using a 25 cm open block and a 250 cm snout. We compared the range distribution by ionization chamber in water phantom and CCD camera scintillation screen system. The difference of the range distribution was within standard deviation 713

in acceptance level (less than 2.0%). Then, this study analyzed the dose distribution of 2D images using CCD camera - scintillation screen system. The light output on scintillation screen and dose distribution obtained from TPS for uniform scanning beam is less than 20% at distal fall-off region. M21-15, Improved accuracy of image guided radiation therapy (IMRT) based on bone suppression technique R. Tanaka1, S. Sanada1, M. Oda2, M. Suzuki2, K. Sakuta3, H. Kawashima3 1

Dept. of Radiological Technology, Kanazawa University, Kanazawa, Japan Dept. of General and Cardiothoracic Surgery, Kanazawa University Hospital, Kanazawa, Japan 3 Dept. of Radiology, Kanazawa University Hospital, Kanazawa, Japan 2

Purpose: A recently developed image processing methodology, the bone suppression technique, can suppress the conspicuity of bones on chest radiographs, creating sort of soft-tissue images obtained by the dual-energy subtraction technique. This study was performed to evaluate the usefulness of bone suppression fluoroscopy in real-time tracking radiation therapy. Methods and Materials: Dynamic chest radiographs of 9 patients with lung nodules during respiration were obtained using a flat panel detector (FPD) system (CXDI-50RF; Canon Inc.) (120 kV, 0.1 mAs/pulse, 5 fps, SID = 1.0 m). Commercial bone suppression image-processing software (SoftView version 2.0; Riverain Medical) was applied to the dynamic chest radiographs to create corresponding bone suppression images. Automatic target tracking was conducted with in-house software based on the template matching technique. To evaluate the accuracy of target tracking, the maximum tracking error in the resulting images was compared between bone suppression and conventional fluoroscopic images. Results: The accuracy of target tracking was significantly improved in 8 of 9 cases. The average maximum tracking errors in bone suppression and conventional fluoroscopic images were 1.31.0 mm and 3.313.3 mm, respectively. The bone suppression technique was especially effective in the lower lung area where pulmonary vessels, bronchi, and ribs showed complex movements. Conclusion: The bone suppression technique improves tracking accuracy without special equipment and additional patient dose in real-time tracking radiation therapy. Our results indicated its usefulness especially in the lower lung area with complex movements of lung structures and ribs. M21-16, Washout Studies of in-Beam Rat Imaging by the 2nd Generation OpenPET Prototype Y. Hirano, E. Yoshida, H. Wakisaka, Y. Nakajima, F. Nishikido, H. Ito, T. Yamaya Department of Biophysics Molecular Imaging Center, National Institute of Radiological Sciences, Chiba, Japan

In-beam positron emission tomography (PET) is expected to be suitable as an in situ dose verification technique in particle therapies. For accurate dose verification, washout of positron emitters should be corrected. In addition, the quantitative washout rate has a potential usefulness as a diagnostic index such as for blood flow and stage of cancer progression. In this work, therefore, we applied compartment analyses to in-beam PET data acquired by the 2nd generation small OpenPET prototype. The OpenPET is our original idea for the open-type PET geometries, which enables PET scanning during irradiation in particle therapies. Two rat brains and two rat 714

thighs located at the field-of-view were irradiated by a 11C beam. Time activity curves of the irradiated field were measured immediately after the irradiations, and the washout rate was calculated based on the two-washout model (medium decay, k2m; slow decay, k2s) developed in a previous study of rabbit irradiation reported by Mizuno et al. For brain irradiations, k2m and k2s were respectively, 0.37 and 0.008 [min-1]. For thigh irradiations, these were 0.34 and 0.008 [min1]. These results were consistent with the rabbit study. Also k2m of brain irradiation was close to the washout rate in cerebral blood flow measurements by dynamic PET with 15O-water. Our present work suggested the k2m may be relevant to blood flow. M21-17, Portal Image Registration Using the Phase Correlation Method G. V. Gerganov1, A. Papucharov2, I. Kawrakow3, K. K. Mitev1 1

Department of Physics, Sofia University, Sofia, Bulgaria Specialized Hospital for Active Treatment in Oncology, Sofia, Bulgaria 3 ViewRay Inc., Cleveland, Ohio, USA 2

Precise patient positioning is a very important step in radiotherapy planning and treatment procedures. Positioning is usually performed by aligning a radiograph to a reference image and using the obtained alignment parameters to move the patient to the required position. To automate the positioning process, a fast and accurate image registration technique is usually required. In this work we investigate the performance of the phase correlation method (PCM) as a registration tool for Electronic Portal Imaging Device (EPID) images. We propose the usage of the PCM method for fast and accurate rigid registration of misaligned EPID images. To illustrate the concept, EPID image are obtained on a Siemens PRIMUS Linear Accelerator by irradiating two different phantoms - a standardised contrast and spatial resolution phantom ("Las Vegas" phantom) and a realistic phantom of a human pelvis area. Each of the phantoms is placed at the patient table and several images at different table positions are acquired. The position of the table at each image acquisition provides information about the true displacements between the obtained images with a millimeter-level precision. In order to evaluate the accuracy of the registration with the PCM, the obtained translational parameters using the method are compared with the true displacements known from the table positioning. The obtained results show that the method provides very accurate shift estimation with a millimeter-level precision. The method can find potential applications in the calibration and quality assurance procedures of this type of linear accelerator systems. The authors anticipate that the PCM can find application for patient positioning not only by registration of EPID images, but with images from other projection-based imaging modalities as well. M21-18, Preliminary Study of Intensity Weighted Region-of-Interesting Image Reconstruction Using Iterative Algorithm K. Son1,2, J. Lee1, Y. Lee1, J. S. Kim2, S. Cho1 1 2

Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Korea Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea

For its wide use, computed tomography (CT) particularly including cone beam CT is challenged by the risk of overdose to the patients. Therefore, reduction of radiation dose is the most important feature in new CT techniques or applications. In this study, we combined the two approaches 715

together to achieve an ultra-low-dose imaging: a sparse-view imaging and the intensity-weighted region-of-interest (IWROI) imaging. IWROI imaging technique is particularly interesting because it can reduce the imaging radiation dose substantially to the structures away from the imaging target, while allowing a stable solution of the reconstruction problem in comparison with the interior problem. We used a total-variation (TV) minimization algorithm that exploits the sparseness of the image derivative magnitude and can reconstruct images from sparse-view data. We divide the reconstructed image into the inner and outer regions at projection images and added noise at the outer regions to make an ROI region. The CT scanning was simulated numerically using CT projection data of the XCAT phantom. The total number of projections was 600 and 120, and the scan range was 360 degrees. Then, these projection images were reconstructed by use of a conventional analytic algorithm, FeldkampDavisKress (FDK) algorithm, from densely angularsampled 600, and 120 projections. Also, projection data were reconstructed by the TV algorithm from sparsely angular-sampled data, or from 120 projections. ROI reconstructed image from the TV algorithm displays better image quality than FDK-120 views, and structures and shape of inner and outer ROI region are well reconstructed compared to the reference imaging. We obtained promising results and believe that the proposed scanning approach can help reduce radiation dose to the patients while preserving good quality images for applications such as image-guided radiation therapy. M21-19, Conceptual design of molecular-image-guided radiotherapy using a parallel plane PET M. Ishikawa1, S. Yamaguchi2, S. Tanabe3, N. Ukon1, K. Sutherland1, N. Miyamoto1, R. Suzuki4, N. Katoh5, K. Yasuda5, H. Shirato5 1

Dept. of Medical Physics and Engineering, Graduate School of Medicine, Hokkaido University, Sapporo, Japan Dept. of Radiology, Iwate Medical University, Morioka, Japan 3 Dept. of Radiotherapy, Keiyuukai Sapporo Hospital, Sapporo, Japan 4 Dept. of Medical Physics, Hokkaido University Hospital, Sapporo, Japan 5 Dept. of Radiology, Graduate School of Medicine, Hokkaido University, Sapporo, Japan 2

[Introduction] Molecular imaging is an important modality for recognizing tumor location, it may be possible to accurately confirm that the irradiation field adequately covers the tumor. We are trying to apply a planar molecular-image for tumor position verification during radiotherapy. A feasibility study on a PET-Linac system for patient setup verification using a parallel-plane PET configuration. [Materials and Methods] Monte Carlo simulations using Geant4 were performed on a simple geometry for patient setup verification. Acquisition time was assumed to be 60 seconds, and the planar image was reconstructed using an ML-EM algorithm. To evaluate the feasibility of molecular-imaging based setup verification, 3 observers were asked to determine the setup displacements using an in-house software which allowed the co-registration of the original image and reconstructed image. [Results and Discussion] The average discrepancies at higher contrast were less than 1.46 mm for all spherical-source diameters. Even at low contrast, average discrepancies were less than 1.20 mm for the spherical sources with diameters larger than 16 mm. It means that accurate patient setup can be done independent of the contrast. Recognition of the 8 mm spherical source was difficult at lower contrast, however, setting the contrast higher than 1:20 resulted a discrepancy of less than 1.15 mm. Actual contrast in the reconstructed image strongly depends on reconstruction algorithm, further development for the algorithm will be needed. [Conclusions] Conceptual design of parallel-plane PET system was considered for the initial patient setup verification in radiation therapy. From the Monte Carlo simulations performed for a simple geometry, molecular-imaging based patient setup verification was found to be feasible up 716

to an accuracy of about 1.5 mm. Moreover, spatial resolution was judged as sufficient for verifying that the irradiation field adequately covers the tumor. M21-20, Exploration of Optimization-Based Reconstruction Potential in Cone-Beam CT for Image-Guided Radiation Therapy X. Han, E. Pearson, E. Y. Sidky, C. A. Pelizzari, X. Pan The University of Chicago, Chicago, IL, USA

Linear-accelerator (LINAC) integrated, cone-beam computed tomography (CBCT) systems are routinely used for image-guided radiation therapy (IGRT). In recent years, significant progress has been made on optimization-based image-reconstruction algorithms, which have demonstrated advantages over conventional, analytic-based algorithms in a number of scenarios. However, CBCT image quality has yet to be explored for its full potential under conditions of practical IGRT interest by use of optimization-based reconstruction. In this work, physical phantom and patient data were collected under imaging configurations of clinical IGRT interest, and we investigate and exploit the CBCT image-quality potential via adaptation of an optimization-based algorithm for reconstruction. We carried out characterization studies for qualitatively and quantitatively assessing the merit of the optimization-based algorithm for specific imaging tasks. The results show that appropriately designed optimization-based algorithms can yield CBCT images of comparable or potentially improved quality from full- and reduced-view data. The results have the implications of improving the CBCT utility for current clinical IGRT applications, as well as potentially enabling novel, low-dose IGRT applications. M21-21, Feasibility of Using O-18 Enriched Phantoms for PET Verification of Proton Therapy Treatment Planning K. Grogg1, X. Zhu1, J. Chang2, B. Winey3, J. A. Correia1, G. El Fakhri1 1

Dept. of Radiology, Mass General Hospital, Boston, MA, USA Florida Radiation Oncology Group, Jacksonville, FL, USA 3 Dept. of Radiation Oncology, Mass General Hospital, Boston, MA, USA 2

We propose using 18O-enriched phantoms for PET verification of proton therapy treatment planning with complex, realistic geometries. Proton therapy is sensitive to range inaccuracy because most of the radiation dose is delivered near the end of the beam known as the Bragg peak. A realistic phantom is desirable to evaluate range uncertainties introduced when different algorithms of treatment planning are used, especially if there are regions with high tissue heterogeneities in the beam path. The 18O (p,n)18F reaction has a low energy threshold and high cross sections near the threshold, resembling the dose-depth distribution of a proton beam, therefore making it possible to evaluate the range uncertainties of different treatment strategies and systems by PET imaging of proton induced F-18 distributions in 18O-enriched phantoms. For a feasibility study we irradiated a phantom with three 2.5-cm tubes filled with 16O/18O water ratios of 100:0, 50:50 and 20:80 (all solidified with 4% gelatin) with a spread-out Bragg peak field with 10-cm water-equivalen (WE) range, 6-cm WE modulation, and a dose of 48 Gy. The activity produced was imaged on a Siemens Biograph scanner for 120 minutes with a 126-minute delay for an F-18 dominated distribution. The PET measured F-18 activity distribution profiles were 717

compared to the planned dose profiles along the beam direction. The differences in distal falloff depths were determined by shifting one distribution until the residual sum of squares between the falloff curves was minimized. The F-18 activity was reliably 2%+-0.5% deeper than the dose falloff depth. PET range verification in an O-18 enriched phantom is feasible due to the consistent agreement between F-18 PET and dose falloffs. Such a phantom system is valuable for proton therapy quality assurance, treatment planning system evaluation and for the assessment of other in vivo range verification methods. M21-22, Optimizing Secondary Radiation Imaging Systems for Range Verification in Hadrontherapy I. Torres-Espallardo1, J. E. Gillam1, P. Solevi1, P. G. Ortega2, H. Rohling3, P. Botas1, J. F. Oliver1, G. Llosa1, C. Solaz1, M. Trovato1, C. Lacasta1, M. Rafecas1,4 1

IFIC (Universidad de Valencia / CSIC), Valencia, Spain CERN, Geneva, Switzerland 3 OncoRay, Technische Universitaet Dresden, Dresden, Germany 4 Departamento de Fisica Atomica, Molecular y Nuclear, Universidad de Valencia, Valencia, Spain 2

Hadrontherapy (HT) aims to treat tumors by maximizing the dose released to the target and sparing the dose to healthy tissues. For a successful outcome it is very important to know where the maximum dose is deposited and therefore range verification is necessary for treatment optimization and patient safety. Secondary positron emitting isotopes and prompt gamma radiation are produced after the hadron beam passage. This secondary radiation coming from tissue activation could be used for quality control of treatment, provided that it can be detected and employed to reconstruct the beam path using imaging techniques. This is the goal of the ENVISION project, to evaluate and develop on-line monitoring devices for HT, like PET for detecting the annihilation photons from positrons and Compton Camera (CC) for prompt gamma radiation detection. In both technologies high sensitivity is required to increase the signal-to-noise ratio of the reconstructed image for a given therapetic dose. This simulation study is focused on the sensitivity optimization of such devices, PET and CC, taking into account its use and constraints for on-line HT monitoring. Several configurations of both technologies have been investigated using sources generated from hadron beams. In the case of PET data, the time-offlight (TOF) information has been included too. For individual hadron beams acquired after 5 minutes, differences in range of 3 mm are detected for all the PET configurations, except for the partial-ring of 60 cm diameter. In addition, patient data from a carbon ion treatment at GSI have been simulated and reconstructed. The system with higher sensitivity and angular sampling recovers more accurately areas with no activity (nasal cavity). In the case of the CC data, the quality of the reconstructed image when using 2-interaction events is notably improved when the detector layers are placed covering a larger solid angle. It is plan to include spurious data and evaluate more patient data. M21-23, Feasibility Study of Proton Radiography in Proton Beam Therapy B. Min1, J. Kwak2, J. Lee3, S. Cho3, D. Shin4, S. B. Lee4, S. Y. Park5, H. Nam1 1

Department of Radiation Oncology, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, KOREA 2 Department of Radiation Oncology, Asan Medical Center, Seoul, KOREA 3 Department of Nuclear and Quantum Engineering, KAIST, Daejeon, Korea

718

4 5

Proton Therapy Center, National Cancer Center, Gyunggi-do, KOREA McLaren Proton Therapy Center, McLaren Cancer Institute, MI, USA

The aim of this study is to evaluate the imaging properties of proton radiography and to evaluate the feasibility as an alternative to conventional portal imaging. The passively scattered proton beams accelerated up to 230 MeV by the cyclotron was used. Dedicated photon-like proton beam was generated for proton imaging, because the normal proton beam could not generate optical density difference. Three different depth-dose distributions generated by beam energy modulation were utilized to investigate their effects on the density and spatial resolutions of the radiographic imaging. Electron density cylinder blocks with diameter of 28 mm and height of 70 mm and a rat were employed to assess the imaging characteristics. The Gafchromic EBT films were utilized for proton radiography. Measured photon-like proton beams have linearity from 30 mm to 180 mm in the water. We found that a steeper slope could provide better resolution for the matching density of phantoms. The resolution of proton images for different kinds of phantoms and imaging qualities was evaluated in comparison with x-ray images. The images for linear and L shape beam show that the location of high-density resolution is opposite across the depth of the phantom. The spatial resolution decreases with the distance because the spatial correlation of the exiting beam with the phantom deteriorates quickly as the image plane moves away from the phantom. We obtained high-quality radiographic images using a rat. The proton imaging performance could be improved with proper shaping of the dose distribution in depth. The high-density resolution of proton radiography is feasible and can be applicable for image guided proton therapy. M21-24, Noise Evaluation of Prompt-Gamma Technique for Proton-Therapy Range Verification Using a Compton Camera P. G. Ortega1,2, I. Torres-Espallardo1, T. T. Boehlen2, F. Cerutti2, M. P. W. Chin2, A. Ferrari2, J. E. Gillam1, C. Lacasta1, G. Llosa1, J. Oliver1, M. Rafecas1, P. R. Sala3, P. Solevi1 1

IFIC (CSIC/UV), Valencia, Spain CERN, Geneva, Switzerland 3 INFN, Milano, Italy 2

The high sensitivity of Compton Cameras (CC) and their potential use for hadron-therapy realtime monitoring through prompt-γ (PG) detection have attracted many research efforts. CC consist of several layers of scintillator material in which photons interact via Compton scattering. However, the broad energy spectrum of PG complicates the development of both fast and accurate reconstruction algorithms useful for real-time purposes. A high efficiency in different layers is desirable to have a high rate of coincidences compared to single events, in order to have a large signal-to-noise ratio. Nevertheless, high intensity beams may produce pile-up in the detector, which may lead to random coincidences, meaning events composed of several hits produced from different incoming photons which produce fake signals. On the other hand, the importance of neutrons as a source of noise has been pointed out in past studies and their influence on the final image may be relevant. The estimation of the range through PG may be affected by these noise sources. For that reason, the evaluation of the noise in a clinically relevant case, where the time structure of the beam is included, is necessary for validating the effectiveness of CC. In this study a Monte Carlo (MC) analysis on the effect of neutrons and a micro-time structure typical for therapeutic beams in the final reconstructed image is presented using FLUKA. All the detection chain, from the proton beam impinging in the target to the detection and selection of events according to a chosen time window are simulated with the FLUKA MC code. The detection of 719

random coincidences for a two and three interaction reconstruction algorithms is evaluated for 100, 140 and 180 MeV monoenergetic pencil proton beams. The accuracy of the range location is studied in different clinical-based scenarios. Both the γ random coincidences and neutron contribution are explored, and their effect in the final reconstructed image is analyzed. M21-25, Monte Carlo Simulation of Region-of-Interest Reconstruction for Real-Time Tumor Tracking by OpenPET H. Tashima1, E. Yoshida1, T. Shinaji2, H. Haneishi3, H. Ito1, T. Yamaya1 1

Molecular Imaging Center, National Institute of Radiological Siences, Chiba, Japan Graduate School of Engineering, Chiba University, Chiba, Japan 3 Research Center for Frontier Medical Engineering, Chiba University, Chiba, Japan 2

We are developing the OpenPET which can provide an open space to make the patient observable and accessible during PET measurements. In addition, we have proposed a real-time imaging system for the OpenPET which is expected to be used in PET-guided tumor tracking radiation therapy. We conducted a feasibility study on tumor tracking using 18F-FDG by Monte Carlo simulation of a human body-sized OpenPET and showed that the tumor tracking is feasible with a time window of 0.5 s if the tumor contains sufficient radioactivity. Although we have demonstrated real-time tumor tracking using a small OpenPET prototype, the delay was 2 s. On a human body scale, the image matrix size become huge compared to the body size of the small prototype and delay can be increased. Therefore, further improvement of the reconstruction speed is essential. From this viewpoint, image reconstruction of the entire field-of-view (FOV) is time consuming and not required for the purpose of tumor tracking. In this study, we developed a region-of-interest (ROI) reconstruction method for the OpenPET and evaluated the tumor tracking accuracy. Although conventional wisdom states that the ROI reconstruction requires a priori information of a small region inside the ROI and 180° scanning without angular truncation for accurate image reconstruction, the computer simulation showed that the ROI reconstruction method without any a priori information had equivalent accuracy in terms of tumor tracking compared with the case reconstructing the entire region. The ROI reconstruction M21-26, Monte Carlo Simulation Study of In-beam Intra-treatment PET Imaging for Adaptive Proton Therapy K. Lou1,2, D. Mirkovic3, X. Sun2, X. R. Zhu3, J. W. Clark, Jr.2, Y. Shao1 1

Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA Department of Electrical and Computer Engineering, Rice University, Houston, TX, USA 3 Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, TX, USA 2

Monte Carlo simulations were conducted to investigate the feasibility to measure the proton beamrange with few beam spills before the treatment to provide rapid feedback for treatment plan verification and re-planning (if necessary) for improving the accuracy of treatment targeting: a potentially novel intra-treatment image-guided adaptive proton therapy. Talys and MCNPX packages were used to generate the distributions of positron emitters in a uniform cylinder phantom irradiated by a collimated 200MeV pristine proton beam with total 50 spills (0.5sec spill with ~100M protons, 1.5sec between spills). An high resolution (1.7mm) and high sensitivity (peak 53%) in-beam prototype PET (61mm in-plane and 30mm axial FOV) with depth-of720

interaction (DOI) measurement was simulated with GATE for imaging. The images were reconstructed with list-mode MLEM algorithm using simulated coincidence data accumulated from during- and post-radiations. Beam-ranges were measured as a function of number of spills, total acquisition time, number of recon iterations, and DOI resolutions. Some simulated results were well validated with real PET acquired data from proton interactions under the same setup and irradiation conditions. Results show that accuracy of beam-range measurement is a function of data statistics but converging rapidly within few beam spills under simulated conditions; few spills can be sufficient to measure the beam-range within 1.0mm from the final converged value if with DOI-measurement; the number of spills can be further reduced if acquiring 30-60sec postradiation time, which is still considered a rapid intra-treatment imaging. The accuracy of beamrange measurement was also calculated as a function of reconstructed count-statistics under the simulated conditions, providing a general and very useful guideline to calculate the required inbeam imaging statistics for accurate beam-range measurement, which is possibly independent of system specifications. M21-27, Observation of Tumor Morphological Changes in Lung Irradiation with Orthogonal Ray Imaging: a Simulation Study H. Simões1, P. Crespo1,2 1 2

LIP - Coimbra, Coimbra, Portugal Physics Department, University of Coimbra, Coimbra, Portugal

Orthogonal ray imaging is a new imaging technique that consists in detecting radiation dispersed in the patient and emitted at right angles in respect to the beam axis. It comprises two concepts: RTmon for real time radiotherapy monitoring, addressed here, and OrthoCT for low-dose morphologic imaging, mainly on-board imaging for assisting radiotherapy (not addressed in this communication). In this work we report Geant4 simulation results analyzing the capability of RTmon to detect (1) a pertinent lung tumor deviation of 9.36 mm in the craniocaudal direction, and (2) a lung tumor shrinkage of 9.36mm. At this stage, the original tumor has a density equal to that of water, having a spherical shape and a diameter of approximately 30 mm. It must be stated that the two aforementioned tumor morphological changes represent clinically relevant scenarios. Tumor dislocation in lung irradiation is an extremely hot topic in all forms of radiotherapy. A beam missing the dislocated tumor will represent an underdosage that may be strongly correlated with tumor relapse. On the other hand, the detection of tumor shrinkage in lung irradiation may allow for a reduction of the dose field, which represents an important relief of the dose burden to the surrounding healthy lung. It is well known that healthy lung tissue subject to radiotherapy doses will result in fibrosis which heavily impairs respiratory function. The counts distributions obtained show a very high visual correlation both with the simulated, prescribed dose, and with the tumor location. Therefore, this technique is likely to represent a high potential asset for imageguided radiation therapy (IGRT), adaptive radiation therapy (ART), and real-time radiotherapy dose verification. M21-28, GGEMS-Brachy: Fully GPU Geant4-Based Efficient Monte Carlo Simulation for Brachytherapy Applications Y. Lemarechal1, J. Bert1, N. Boussion1, E. Le Fur2, D. Visvikis1

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1 2

LaTIM - INSERM UMR1101 - CHRU Brest, Brest, France Radiotherapy department, CHRU Brest, Brest, France

In brachytherapy, dosimetric plans are routinely calculated with the TG43 formalism which considers the patient as a simple water box. However, accurate modelling of the physical processes considering patient heterogeneity using Monte Carlo (MC) methods is currently too time-consuming and computationally demanding to be routinely used. As a solution we implemented an accurate and fast MC simulation based on Geant4 on graphics processing units (GPU) for brachytherapy applications. Existing approaches using GPU architecture for brachytherapy MC simulations suffer from numerous approximations including, the use of virtual seed bound to a phase space file to define dwell sources, or removing voxel within the CT image to include seed density. Within the proposed framework such approximations have been removed. A comparison between dosimetric plans based on the current clinical standard (TG43) and the proposed full MC simulation led to substantial differences due to the TG43 related approximations assuming the patient as a water box. Finally, the proposed dosimetry platform is capable of providing accurate dose distributions within one minute, which is compatible for a clinical routine usage. M21-29, Proton Dose Verification in the Murine Model with Positron Emission Tomography of Activated Radioisotopes. M. J. Nyflot1, E. C. Ford1, S. R. Bowen1,2, G. Battistoni3, R. Nicolini3, M. Narayanan1, E. F. Dorman1, R. Emery1, P. E. Kinahan2, G. A. Sandison1, A. Del Guerra4, R. S. Miyaoka2 1

Dept. of Radiation Oncology, University of Washington, Seattle, WA Dept. of Radiology, University of Washington, Seattle, WA 3 Sezione di Milano, INFN, Milano, Italy 4 Dept. of Physics, University of Pisa, Pisa, Italy 2

Objective: Proton therapy is characterized by a sharp fall-off in dose at the distal edge of the Bragg peak, which offers therapeutic benefits but also a need for verification of proton range in the patient. We imaged proton-activated organic radioisotopes in the murine model, and used Monte Carlo simulations to correlate radiation dose to PET activation. Methods: To measure proton activation, a mouse cadaver was irradiated with a 50 MeV proton beam to 20 Gy at 2 mm depth, with end of bombardment at 7:33 (minutes:seconds). Following irradiation, PET images were acquired starting at 10:20 in a Siemens Inveon microPET scanner for 20 mins. Following PET imaging, CT images were acquired on a GE Discovery CT scanner. CT and PET attenuation scans were rigidly co-registered and the resulting registration was used to fuse PET/CT images. CT images were converted to voxel geometries in FLUKA v2011.2b and proton dose and PET activity were simulated. As a first approximation, only activity from C-11, N-13, and O-15 was considered. Results: Simulated proton dose distributions showed strong agreement with reference data, with proton range of 21 mm in the mouse versus 22 mm in water. Proton activation was readily measured in the mouse, with maximum PET activation of 534 Bq and depth of activation of approximately 14 mm. Simulated PET activity produced depth of proton activation of approximately 16 mm and demonstrated good qualitative agreement with experimental results. Conclusions: Measurement and simulation of proton-activated radioisotope production is feasible in a murine model. Going forward, in-room PET detection as well as improved modeling will be investigated to compensate for the short-lived radioisotopes and known challenges in the nuclear physics simulation. In conclusion, PET imaging of proton-activated radioisotopes shows strong 722

promise for dose verification of precision radiotherapy applications. M21-30, Assessment of Microsoft Kinect Technology (Kinect for Xbox and Kinect for Windows) for Patient Monitoring During External Beam Radiotherapy F. Tahavori1, P. Elangovan1, M. Alnowami2, R. Yamani1, E. Donovan3, K. Wells1 1

Electronic engineering Department, CVSSP, University of Surrey, Guildford, Surrey, UK Nuclear Engineering Department, King Abdulaziz University, Jeddah, Kingdom of Saudi Arabia 3 Joint Department of Physics, Royal Marsden NHS Trust, Sutton, Surrey, UK 2

In this study, the technical performance of Kinect for Xbox and Kinect for Windows were assessed to use for external beam radiotherapy. Two sets of experiments were performed to address this issue. In the first experiment, a plain test card and an optical rail were used to assess system performance quantitatively. In the comparison of the errors of both systems, the Windows version produces superior performance compared to the Xbox version for the target placed at a distance of 60-140 cm. Moreover, the use of Xbox and Windows Kinect for monitoring respiratory motion, both in supine and prone positions, were also investigated. Preliminary data suggests that Kinect technology may be useful for monitoring deep as well as tidal breathing, and thus may be useful for gating during dose delivery. A more in-depth investigation, with a greater variation of body morphologies will be included in the final paper. This will also include a detailed study of the Kinects potential using a Galil (DMC 4060) motion controller. Galil can be use to create a synthetic motion with sub mm accuracy. M21-31, Full Inverse Treatment Planning in Spot-Scanning Ion Therapy M. C. Robini, N. Freud, J.-M. Letang CREATIS (CNRS UMR5220 and INSERM U1044), INSA Lyon, Villeurbanne, France

Spot-scanning ion therapy (SSIT) is a state-of-the-art radiation therapy technique which uses pencil beams of protons or heavier ions (such as carbon) to irradiate a target volume (TV) while sparing the surrounding healthy tissues and the organs at risk (OARs). This technique has multiple degrees of freedom (notably the beam trajectories, energies and fluences), which raises the problem of inverse treatment planning: how to find an optimal setting for matching the dose prescribed in the TV without irradiating the OARs? Inverse treatment planning has been extensively studied in the field of photon-beam radiation therapy, but most associated methods do not apply to SSIT. Furthermore, the approaches available for SSIT are essentially iterative descent methods that optimize the beam fluences once the beam trajectories and energies are fixed. We propose an efficient simulated annealing (SA) approach to what we call the full inverse treatment planning (FITP) problem in SSIT. The goal of FITP is to find the optimal trajectories, energies and fluences of the beams given their number and transverse profile. This joint optimization problem is rarely considered for it is a challenging optimization task. Our contribution is twofold: (i) we show that FITP can be performed accurately by using SA, and (ii) we construct an efficient candidate-solution generation mechanism that substantially speeds-up the annealing process without altering its global convergence properties (the obtained speed-up factor is of the order of 100).

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M21-32, Dual-Head in-Situ Vs. Full-Ring in-Room TOF-PET for Quality Assurance in Proton Therapy: a Clinical Case Study P. Dendooven 1, H. J. T. Buitenhuis1, F. Diblen2, D. C. Oxley1, A. Biegun1, A. J. van der Borden3, S. Brandenburg1, P. Cambraia Lopes4, A. van der Schaaf3, D. R. Schaart4, S. Vandenberghe2, A. A. van 't Veld3 1

KVI, University of Groningen, Groningen, Netherlands MEDISIP, Department of Electronics and Information Systems, Ghent University, Ghent, Belgium 3 Department of Radiation Oncology, University Medical Center Groningen, Groningen, Netherlands 4 Radiation Science & Technology Department, Delft University of Technology, Delft, Netherlands 2

In order to determine the clinical benefit of positron emission tomography (PET) for dose delivery verification in proton therapy, we performed a patient case study comparing in-situ with in-room time-of-flight (TOF) PET. For the in-situ option, we consider both a (limited-angle) clinical scanner and a dual-head scanner placed close to the patient. Geant4-based Monte-Carlo simulations of the treatment plan of a typical head & neck clinical case result in the distribution of the production of the 7 most relevant PET isotopes. Radioactive decay during irradiation is taken into account; biological washout is not. GATE is used to simulate PET imaging, with coincidence resolving time and limited angular coverage applied to the GATE output data. The original treatment plan was also simulated for patients with artificially introduced anatomical changes. The visibility at the distal edge of the irradiation in the TOF-PET images of the effect of the anatomical changes will be related to the scanner geometry/protocol and timing resolution. The maximum number of detected coincidences, 3.36 million for an SOBP physical dose of 0.46 Gy, is obtained for the full-ring in-situ clinical scanner. The dual-head scanner results in a number of coincidences equal to that of a full-ring in-room scanner. An in-situ clinical scanner needs an angular coverage of more than 2/3 to acquire the same number of coincidences as the dual-head scanner. We conclude that both an in-situ dual-head and an in-room full-ring clinical TOF-PET scanner deliver comparable image quality: they detect a comparable number of coincidences and state-of-the-art TOF detector performance can eliminate the limited-angle image artefacts of the dual-head scanner. The dual-head configuration has the advantage of minimising the effect of biological washout. Given that its detector area is just 1/6th that of a full-ring clinical scanner, it is an economic solution as well. M21-33, 18F-FDG imaging to evaluate radioactive 198Au-gold nanoparticle (R-GNP) therapy for orthotopic brain tumor model S. Y. Chen, C. H. Chen, C. Y. Chen, C. H. Chen, W. N. Liao, J. K. Chen, C. S. Yang Center of Nanomedicine Research, National Health Research Institutes, Miaoli County, Taiwan

The annual incidence of malignant primary brain tumor is 5 to 19 cases per 100,000 people, more than 50% cases are glioblastoma multiform (GBM). The surgical resection is standard treatments for newly diagnosed GBM patients. However, surgery can not completely eliminate GBM owing to its infiltrative nature. The radioactive 198Au-gold nanoparticle (R-GNP) can emit beta particle to treat inoperable tumor cells nearby the margin of surgical resection. The 18F-fluoro-deoxyglucose (FDG) takes advantage of differentiating necrotic tissue from viable tumor tissue in brain. The aim of this study is to establish the animal model with orthotopic glioblastoma to demonstrate the RGNP therapy efficacy using FDG image. The mixture solution of comprising natural gold ions with polyethylene glycol was subjected to 724

nuclear reactor to synthesize R-GNPs. C6 glioblastoma cells were implanted in brain of Wistar rats. Twelve days after implantation, the brain tumor was evaluated using positron emission tomography (PET) with co-registration of computed tomography (CT) scanning. The rats were sacrificed on the day after the last imaging and the brains were taken out for TUNEL assay and H&E stain to observe cell apoptosis and necrosis. Before therapy, PET images show FDG uptake in tumor region abnormally higher than in normal brain tissue. The image 5 days after therapy did not show obviously increased uptake of FDG in brain. The brain tissue around R-GNP was displayed apoptosis and necrosis phenomenon, corresponding to lower FDG uptake on PET image after therapy. The maximum survival of control group was 21 days (0% of survival rate) after tumor cell implantation whereas animals treated with R-GNP showed 87.5% survival rate. Based on integrated evaluation of PET/CT images, histology and survival curves, we have observed a promising increase of survival rate, implying significant suppression of tumor progression by the R-GNP introduced in our study. M21-34, Performance Evaluation of SensL SiPM Arrays for High-Resolution PET J. D. Thiessen1, C. Jackson2, K. O'Neill2, D. Bishop3, P. Kozlowski4, F. Retire3, V. Sossi5, C. J. Thompson6, A. L. Goertzen1 1

Department of Radiology, University of Manitoba, Winnipeg, MB, Canada SensL, Cork, Ireland 3 Detector Development Group, TRIUMF, Vancouver, BC, Canada 4 Department of Radiology, University of British Columbia, Vancouver, BC, Canada 5 Department of Physics & Astronomy, University of British Columbia, Vancouver, BC, Canada 6 McConnell Brain Imaging Centre, Montreal Neurological Institute, Montral, QC, Canada 2

Silicon photomultipliers (SiPMs) have high gain, excellent timing performance, and are well suited to PET/MRI applications due, in part, to their MR-compatibility and small form factor. Within the constraints of a resistor-based multiplexing circuit, it is useful to evaluate the four generations of SiPM arrays manufactured by SensL: the Array4, Array4SL, Array4SM, and Array4SB. To this end, bias voltage and current were measured as a function of temperature in six Array4s, two Array4SLs, and one each of the Array4SM and Array4SB. With the Array4 and Array4SL, flood histograms were created for 4x4, 9x9, and dual-layer 6x6/7x7 LYSO crystal arrays with energy resolution and resolvability indices measured at overvoltages of 2, 2.5, and 3 V. Measurements of dark current vs. bias voltage increased as temperature increased, with a corresponding increase in the breakdown voltage, Vb. The temperature dependence of Vb is similar between all four generations of SiPM arrays with slopes ranging from 0.0199 to 0.0252 V/°C. Notably, the Array4SB has lower values for the breakdown voltage, with Vb = 23.7 V at 0°C. The predicted dark current at 25°C and band gap energy of silicon were higher in the Array4SL compared to the Array4 when fit to the bias current (at Vb + 2 V) vs. temperature. In terms of resolvability index, flood histograms were slightly better with the Array4SL at Vb + 2.5 V, most noticeably in the dual-layer LYSO array. Likewise, the energy resolution was improved by 7-14% with the Array4SL for all three LYSO arrays. Based on this preliminary data, additional performance improvements are expected from the Array4SM and Array4SB relative to the Array4 and Array4SL when placed in the detector circuit. The linearity of the SensL SiPM arrays as a function of temperature and breakdown voltage makes them a suitable choice for a highresolution, small animal PET/MRI system. 725

M21-35, Performance Uniformity Evaluation of Two SensLs SiPM Array Modules L. Chartier1, Y. Qi1, M. Petasecca1, P. Ihnart1, M. Lerch1, A. Rosenfeld1, B. M. W. Tsui2 1 2

Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia Division of Medical Imaging Physics, Johns Hopkins University, Baltimore, MD, USA

Minimization of the channel-to-channel variation of silicon photomultiplier (SiPM) array is of great importance in achieving high performance for SiPM based imaging detectors. The purpose of this study was to characterize the operating parameters of a large-area SiPM based detector module with 12x12 pixel array (SensLs ArraySM-4P9) in order to develop an optimal multiplexing readout for high-resolution SPECT imaging. Two versions of SensLs SiPM arrays were investigated in this study. The previous ArraySL-4 version has an array of 4x4 pixels with 3x3mm2 pixel size and the new AarraySM-4p9 version consists of a 3x3 matrix of the 4x4 pixels SiPM modules. The current versus voltage (I-V) characteristics of individual SiPM pixels were measured to extract information of its breakdown voltage and dark current. The energy spectrum of individual pixels coupling with a 1x1x3mm3 LYSO crystal was measured using a 137Cs source. The test results show that the previous ArraySL-4 version has larger channel-to-channel variations in breakdown voltage and dark current than the newer AarraySM-4p9 version. The new large-area ArraySM-4P9 SiPM module with 12x12 pixels shows very small breakdown voltage variations within +-0.1V at operating voltage of ~27V and dark current variations within +-0.4nA of ~1nA over the entire 144 pixel elements. The measured energy resolution of an individual SiPM pixel with a 1x1x3mm3 LYSO crystal is ~16% at energy of 662keV. In conclusion, the new SensLs AarraySM-4p9 ArraySM has much better improved property than the previous ArraySL-4 version. The excellent performance uniformity of the large-area ArraySM-4P9 SiPM module is excellent for multiplexed readout approach in the development of high-performance and cost-effective compact imaging detectors. M21-36, A Novel Approach to Position-Sensitive Silicon Photomultipliers: First Results. A. Gola, A. Ferri, A. Tarolli, C. Piemonte FBK, Trento, Italy

In this work, we present a novel Position-Sensitive Silicon Photomultiplier based on a charge sharing architecture. Using four read-out electrodes it is possible to determine the x and y coordinates of a light spot on a large area device. We produced different prototypes with this scheme, ranging from 8x1 mm2 1D to 8x8 mm2 2D position sensitive SiPMs. We coupled the sensors to LYSO scintillator arrays with different pixel sizes, for evaluating the position resolution in the gamma-ray detection. As an example, we were able to resolve the elements of a 6x6 LYSO array, having a pixel pitch of 1.2 mm, with a peak to valley contrast ratio higher than 80 % at 20 C, using 511 keV photons. Further test are ongoing in order to evaluate the ultimate resolution capability of the photodetector. M21-37, A 4x4 Pixilated Silicon Photomultiplier for a Multi-Channel Radiation Monitoring System H. Kim1,2, D. Kim1, S. W. Kim1,3, J. Fowler1

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1

Biosciences Department, Brookhaven National Laboratory, Upton, NY, USA Biomedical Engineering, Polytechnic Institute of New York University, Brooklyn, NY, USA 3 Laboratory of Neuroimaging, National Institute on Alcohol Abuse and Alcoholism, Upton, NY, USA 2

Due to an increase in the use of radiochemistry synthesis systems in Positron Emission Tomography (PET), there is a need for the development of a cost effective radiation detector which can measure localized radiation fields independent of temperature. In this experiment, a 4x4 pixilated Silicon Photomultiplier (SiPM) imaging sensor with optical fiber and Optical Fiber Scintillator (OFS) has been designed and constructed for detecting the β and γ radiation in realtime. It consists of 16 x 1 mm diameter cylindrically shaped scintillators each connected to a single 1 mm diameter optical fiber. Each optical fiber is connected to a separate anode pixel of a 4x4 SiPM via a custom designed holder. In this design each optical fiber and OFS can be a different length, increasing the flexibility of the system. Preliminary detection sensitivity results will be presented based on a GATE simulation. Various geometries are explored to optimize detection of a radiation point source. Due to the use of optical fiber with OFS, long distance, realtime monitoring of radiation is possible. By using OFS, temperature independent radiation monitoring near high and low temperature baths commonly found in radiochemistry systems is possible. M21-38, Comparison of End/Side Scintillator Readout with Digital-SiPM for ToF PET J. Y. Yeom1, R. Vinke1, M. F. Bieniosek2, C. S. Levin1,2,3 1

Molecular Imaging Program at Stanford, Dept. of Radiology, Stanford University, Stanford, CA, USA Dept. of Electrical Eng., Stanford University, Stanford, CA, USA 3 Depts of Physics, and Bioeng., Stanford University, Stanford, CA, USA 2

Side-readout of scintillation light from crystal elements in PET is an alternative to conventional end-readout configurations, with the benefit of being able to provide fine depth-of-interaction (DOI) information and good energy resolution while achieving excellent timing resolution required for time-of-flight PET. In this study, the performance of discrete LYSO scintillation elements read out from the end/side with digital silicon photomultipliers (dSiPM) has been assessed. Compared to 3 x 3 x 20 mm3 LYSO crystals read out from their ends that gave a coincidence resolving time (CRT) of 162 +/- 7 ps FWHM and saturated energy spectra, a sidereadout configuration achieved an excellent CRT of 147 +/- 2 ps FWHM after correcting for timing skews within the dSiPM and an energy resolution of 11.8 +/- 0.2% without requiring energy saturation correction. On the other hand, with smaller 3 x 3 x 5 mm3 LYSO crystals that can also be tiled/stacked to provide DOI information, a timing resolution of 134 +/- 6 ps was attained but produced highly saturated energy spectra. These timing values can further improve by employing brighter/faster crystals like LSO:Ce,Na or LaBr3, and/or by cooling to lower temperatures. M21-39, Effects of Dark Counts on Digital Silicon Photomultipliers Performance R. Marcinkowski, S. Espana, R. Van Holen, S. Vandenberghe MEDISIP, Dept. of Electronics and Information Systems, Ghent University-iMinds-IBiTech, Ghent, Belgium

Digital Silicon Photomultipliers (dSiPM) are solid-state single-photon sensitive devices made of 727

arrays of Geiger-mode avalanche photodiodes, which integrate CMOS electronics into silicon chip for early digitalization of Geiger-cell output. Due to this novel architecture, dSiPMs contain a set of configurable parameters that must be well understood for the optimal use as a gamma photon detector. In particular the dark counts can lead to partial or complete loss of gamma events or to the appearance of noise events uncorrelated with gamma events. The optimal configuration parameters for each application vary depending on the energy of the gamma, the light output and time response of the scintillator and the light spread used to identify the interaction coordinates. In this work we studied multiple combinations of configuration options, such as trigger and validation levels, RTL refreshment or Neighbour Logic, in order to quantify sensitivity loss due to dark counts and provide guidelines on what is the optimal configuration for different detector designs and applications. In our studies we focused on achieving the highest possible sensitivity of the detector based on dSiPM. In particular we studied what would be the best strategy to employ for the detectors based on monolithic crystals or pixelated arrays with small pixel size require, which require a simultaneous readout of several dies in order to process the event. We have found that RTL refreshment is an effective option to reduce dark counts and to ensure 100% sensitivity of the detector regardless of trigger level and number of dies needed per event. Therefore, in cases where the scintillation light is spread into several dies, the use of the RTL refresh option should be employed and be combined with a low validation level in order to guarantee the individual validation of all required dies. We have also found that the dead time of dSiPM is longer then the recharge time and is around 50 ns instead of 20 ns. M21-40, Comparison of SDDs and SiPMs Photodetector Options for INSERT, a New MultiModality SPECT/MRI System for Preclinical and Clinical Imaging P. Busca1,2, M. Occhipinti1,2, C. Fiorini1,2, A. Butt1,2, R. Peloso1,2, R. Quaglia1,2, F. Schembari1,2, P. Trigilio1,2, T. Bukki3, G. Nemeth3, P. Major3, G. Giacomini4, A. Gola4, C. Piemonte4 1

Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milano, Italy Sezione di Milano, Istituto Nazionale Fisica Nucleare, Milano, Italy 3 Mediso Ltd, Budapest, Hungary 4 Fondazione Bruno Kessler, Trento, Italy 2

A new multi-modality imaging tool is under development in the framework of the INSERT (INtegrated SPECT/MRI for Enhanced Stratification in Radio-chemo Therapy) project, supported by European Community. The final goal is to developed a custom SPECT apparatus, that can be used as an insert for commercially available MRI systems such as 3 T MRI with 60 cm bore diameter. INSERT is expected to offer more effective and earlier diagnosis with potentially better outcome in survival for the treatment of brain tumors, first among everything glioma. The basic building block of the SPECT detector ring is a small 5x5cm2 gamma camera, based on the wellestablished Anger architecture with a continuous CsI(Tl) scintillator readout by an array of silicon photodetectors. Silicon Drift Detectors (SDDs) and Silicon PhotoMultipliers (SiPM) have been taken into account as possible scintillator readout, considering that the detector choice plays a predominant role for the final performance of the system, such as energy and spatial resolution, as well as the useful field of view of the camera. Both solutions are therefore under study to evaluate their performances in terms of FOV, spatial and energy resolution. First results on SDDs and SiPMs comparison can be provided, based on simulations and experimental characterization of prototypes. M21-41, Isoelectronic Te Inclusion in ZnSe for Radiation Imaging Application 728

C. D. Lee1, B. Singh2, S. Miller2, V. Nagarkar2 1 2

Materials Engineering, Raytheon, Andover, USA Radiation Monitoring Devices, Watertown, USA

II-VI compound semiconductors have been demonstrated prominent scintillation performance under various ionizing radiations. Besides its superior luminosity, the emission wavelength of the scintillators such as ZnSe:Cu matches to the spectral response of Si imaging detectors with high quantum efficiency of over 95 %. However, self-absorption of the scintillation light becomes an issue to fully utilize the excellent materials properties. Due to inferior spectral transparency associated with spectral region where the self-absorption occurs, film thickness required for the detection of high energy radiation is limited. In this work, we propose to include isoelectronic Te in ZnSe:Cu samples to mitigate the self-absorption. We found that the Te inclusion increases Stokes shift significantly with respect to ZnSe:Cu samples in the excitation spectroscopy. The carriers generated by the ionizing radiation appear to be trapped initially near the Te sites and then they are transferred to Cu sites. Furthermore, micro-columnar ZnSe:Te films grown by vapor deposition demonstrate high spatial resolution, excellent dynamic range, and high contrast sensitivity. M21-42, Amorphous Selenium (a-Se) Avalanche Photosensor for Application in Positron Emission Tomography O. Bubon1,2, G. DeCrencenzo2, J. Rowlands2 1 2

Physics Department, Lakehead University, Thunder Bay, Ontario, Canada Advanced Detection group, Thunder Bay Regional Research Institute, Thunder Bay, Ontario, Canada

The avalanche gain capability of a-Se is of significance to the field of radiation medical imaging as it promises to reproduce the internal gain previously the exclusive domain of vacuum electrooptical devices and SiPM recently. The first practical application of avalanche multiplication was demonstrated by Tanioka et al. in the late 1980s in Japan with a-Se photoconductive target called a High-gain Avalanche Rushing Photoconductor (HARP). Previously avalanche a-Se photo sensors were restricted to electron beam readout that requires vacuum operation [1,2] For use in medical imaging detectors, the new structure of a-Se detector has been developed where electron beam was replaced by a two-dimensional array of metal pixels [3]. Thus allowed advances with investigations of a-Se capabilities as an alternative material for PET. The pulsed height spectroscopy (PHS) experiments were performed using a-Se as a phototarget with metal pixels and a light source with very low intensity emitting blue light photons with the wavelength close to that of light emitted from the scintillation crystal commonly used in PET (LYSO). The unique properties of a-Se, like high quantum efficiency and internal gain, resulted in energy resolution of around 2% in avalanche regime. Encouraged by previous results with light source another PHS experiment was performed. The pixelated a-Se phototarget was optically coupled to the LYSO scintillation crystal. And the Na-22 was used as an external source of radiation. The energy resolution of a-Se for 511 keV peak was less than 15%. These results were not previously achievable with a-Se and were compared with commercially available SiPM. The characteristics above demonstrate that a-Se is a practical approach for the development of a-Se solid-state avalanche photosensor with extremely low dark current, suitable for a applications in PET and a variety of other applications where an extremely sensitive solid state sensor is required with metal electrodes. 729

M21-43, Experimental Performance Evaluation of Commercial Photon-Counting CdZnTe Detector Modules for Medical Applications M. L. Rodrigues, X. Wang, K. Cao, J. Wang, Y. Zou, Y. Zhang, D. Gagnon Toshiba Medical Research Institution U.S.A., Vernon Hills, IL, USA

In this work, we have experimentally evaluated the spectral and count rate performances of a commercial CdZnTe detector module manufactured by eV Products. The detector module consists of an array of pixelated CdZnTe detectors, an application specific integrated circuit (ASIC), associated electronics and an exterior enclosure. Data acquisition was conducted using a commercial software provided by eV Products. In experiments, gamma-rays emitted by Am-241 and Co-57 were used to characterize the spectral performance calculating the energy resolution R as a function of operating conditions (ASIC peaking time Tau and operating field E) and design criteria (detector thickness T). A 140kVp 3mm Al polychromatic x-ray beam was used to characterize the spectral and count rate performance of the detectors at low- and high-flux (~12Mcps/channel) operating conditions. Incident count rates were estimated using a published xray spectrum simulator (SpekCalc, by Poludniowski et al.). Energy spectra were measured by stepping energy window thresholds in small increments. Energy resolution for different CdZnTe detectors was measured at different operating conditions using the 59.5keV and 122.1keV gammarays emitted by the radioisotopes. Total x-ray counts were calculated integrating the measured xray spectra above a 30keV low-energy threshold. Energy resolution, count rate performance, count loss due to pile up and other effects were investigated in order to evaluate the performance of the CdZnTe detectors under low- and high-flux operating conditions. Trade-offs between different design criteria, detector thickness T (T1 = 1mm and T2 = 2mm), ASIC peaking time Tau (Tau1 = 40ns and Tau2 = 80ns), and operating field E (E1 = 300V/mm and E2 = 450V/mm), were investigated and are reported in this work. M21-44, Feasibility Studies on the Organic Semiconductor Radiation Detector for X-Rays H. Park, S. Eom, S. Lim, J. Kang Department of Electronics and Electrical Engineering, Dankook University, Yongin-si, Gyeonggi-do, Korea

Organic semiconductor materials are one of the hot topics which are widely studied in various fields such as a sensors, photovoltaic devices and light-emitting diodes. The advantages of using organic semiconductor materials are ease of fabrications, principle inexpensive, light weight, and fully flexible. Organic semiconductor by taking these advantages can be applied to a variety of applications. One of the possibility applications for organic semiconductor materials is the digital flat-panel imagers (FPIs) for medical x-ray imaging. Organic semiconductor based devices are attractive alternative to the inorganic conventional FPIs technology that mainly based on amorphous silicon. In addition, the radiation hardness and stability of organic photovoltaic device based on a blend of the conjugated polymer are explored to a number of studies. In this study, we have investigated devices for X-ray detectors based on organic semiconductors. The most widely explored organic X-ray detector based on a photovoltaic device is physically coupled to a scintillator. In order to determine the inherent properties of the organic semiconductor, we examined the characteristics of detector via direct detection method. After the examination of direct detection, the indirect detection coupling to a scintillator will be performed. The fabricated 730

devices were based on a thin-film blend of the conjugated polymer P3HT and the fullerene derivative PCBM as active materials. These materials have been widely used as bulk heterojunction photodetectors. This study is undergoing to improve performance of organic detector. M21-45, Characterization of a New Gamma-Ray Detector Based on 16x16 Anode PSPMT Coupled with LaBr3 Scintillator L. Andreani1,2, C. Labanti1,3, F. Fuschino1,3, M. Marisaldi1,3, R. Campana1,3, P. Malcovati4, M. Grassi4, M. Feroci5,6, Y. Evangelista5,6, A. Rachevski7, A. Vacchi7, G. Zampa7, N. Zampa, M. Zuffa1, G. Baldazzi1,2 1

Div. of Bologna, INFN, Bologna, Italia Dept. of Physics and Astronomy, University of Bologna, Bologna, Italia 3 Italian National Institute of Astrophysics, Bologna, Italia 4 Dept. of Electrical Engineering and INFN, University of Pavia, Pavia, Italia 5 INAF/IAPS, Roma, Italia 6 Div. of Roma Tor Vergata, INFN, Roma, Italia 7 Div. of Trieste, INFN, Trieste, Italia 2

We have developed a detection system based on a Position-Sensitive Photomultiplier (PSPMT) Hamamatsu H9500, equipped with 16x16 anodes arranged on a surface of 50x50 mm2. The PSPMT is coupled with a slab of lanthanum tribromide (LaBr3) scintillator. This detector is designed to act as a calorimetric tract for a Compton Chamber we are developing. The tracker part of the Compton Chamber consists of a large area (50x50 mm2) Silicon Drift Detector (SDD) and the calorimeter must also provide the trigger for measuring the time of flight of the charge as it is being collected to the anodes of the SDD. This detector has considerable potential and can also be used in both medical and experimental astrophysics applications. For these purposes the front-end electronics has been designed and built; it consists of 8 VA32_HDR11 ASICs. The electronic trigger, the digitizing system and data transmission over optical fiber were also realized. All circuits have been developed in surface mount technology and fit the dimensions of the PSPMT to obtain a minimum volume detection system. During the testing phase of different scintillators, both segmented and continuous ones were used for a complete characterization of the prototypes. In this presentation we will expose the results obtained in experimental tests. M21-46, Performance Characterization of a New Metal Channel Photomultiplier Tube for Timeof-Flight and High Resolution PET Applications G. B. Ko, J. S. Lee Department of Nuclear Medicine, Seoul National University, Seoul, South Korea

Metal channel PMTs display potential advantages for high resolution PET and TOF PET application. The latest metal channel PMTs, the Hamamatsu R11265 series, have a fast rise time, fast transit time and less transit time spread compared to H8500 series PMTs, the widely used MA-PMTs for high resolution PET application. In this study, we evaluated two 16 channel R11265 PMTs, R11265-100-M16 (super bialkali; SBA) and R11265-200-M16 (ultra bialkali; UBA). The 16 anode signals of R11265 PMT were reduced to 4 position signals by a weighting method. Each position signal was made by weighted sum of 9 closest anode signals. A single 3x3x20 mm3 LGSO crystal was a mounted center of one cell of metal channel PMT for evaluation 731

of performance dependency related to cathode materials and high voltage. The 7x7 LGSO block (3x3x20 mm3) and 9x9 LYSO crystal array (1.2x1.2x10 mm3) were evaluated. Commercial NIM/VME module and LYSO-fast PMT detector were used for coincidence data acquisition. When these PMTs were coupled with single LGSO crystal, UBA shows a slightly better performance than SBA, and the overall performances were improved by increasing high voltage. For the 3 mm block detector, the UBA and SBA show a similar performance outcome. For both of the PMT types, the peak-to-valley ratio in the flood image was above 30, average energy resolution was ~10%, and average coincidence resolving time (CTR) was below 350 ps. Also, the transit time difference between the cell positions was quite small. In case of 1.2 mm block experiment, the crystal size of 1.2 mm was also clearly separated in the flood image, and peak-tovalley ratio was 11. The average energy resolution and average CTR of 81 crystals were 12.7% and 352.8 ps, respectively. The new type of metal channel PMT has promising performance for PET detector especially for TOF application and high resolution PET. SBA seems to be enough for PET block detector made of LYSO/LGSO scintillators. M21-47, The X'tal Cube with 1 mm3 Isotropic Resolution Based on a Stack of Laser-Segmented Scintillator Plates N. Inadama1, Y. Hirano1, F. Nishikido1, H. Murayama1, M. Nitta2,1, H. Ito1, T. Yamaya1 1 2

National Institute of Radiological Sciences, Chiba, japan the Graduate School of Science and Technology, Chiba University, Chiba, Japan

X'tal cube is the 3D position-sensitive radiation detector we have developed. Its structure uses multi-pixel photon counters (MPPCs) that are coupled on all sides of the scintillation crystal block which is segmented into a 3D array of cubes. No reflector is inserted into the crystal block so that scintillation light originating in one of the cubic segment spreads 3-dimensionally and distributes among all MPPCs on the crystal block. We have already succeeded in identifying 18 x 18 x 18 segments of 1 mm x 1 mm x 1 mm in size with a simple Anger-type calculation of the MPPC signals when we used the crystal block having 3D segmentation inside by laser processing (the 3D crystal block). On the other hand, we have explored the possibility of structuring the crystal block by stacking scintillator plates having 2D segmentation by laser processing (a plate crystal block) instead of the 3D crystal block. The 2D segmentation in thin scintillators is much easier to achieve than the 3D segmentation and in the event that the crystal block has a crack, we can exchange the scintillator partially for the plate crystal block. In our previous study, we proved that the plate crystal block has sufficient segment identification ability for a 9 x 9 x 9 array of 2 mm x 2 mm x 2 mm crystal segments. In this study, we aimed for higher spatial resolution and examined the use of 1 mm thick scintillator plates segmented in an 18 x 18 array of 1 mm x 1 mm elements. We used LYSO for the scintillator. Performance of the plate crystal block was compared with that of the 3D crystal block. M21-48, Development of a SiPM based Gamma-Ray Imager Using a Gd3Al2Ga3O12:Ce (GAGG:Ce) Scintillator Array M. Georgiou1,2, S. David2, E. Fysikopoulos2,3, G. Loudos2 1

Medical School, Department of Nuclear Medicine, University of Thessaly, Larissa, Greece Department of Medical Instruments Technology, Technological Educational Institution of Athens, Athens, Greece 3 School of Electrical and Computer Engineering, National Technical University of Athens, Athens, Greece 2

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In this study we present the performance evaluation of a 6x6 Gd3 Al2Ga3O12:Ce (GAGG:Ce) pixellated scintillator with 2x2x5mm3 crystal size elements, coupled to a silicon photomultiplier array (ArraySL-4) . Evaluation was carried out with low energy isotopes i.e. 57Co and 99mTc. A symmetric resistive charge division matrix was used reducing arrays 16 outputs to 4 position signals. A Field Programmable Gate Array (FPGA) Spartan 6 LX16 was used for triggering and signal processing of the signal pulses acquired using a free running sampling technique. Raw images of the crystals maps were acquired. The mean energy resolution at 140keV and 122.1 keV was 16.1+/-0.52% and 18.1+/-0.64% respectively, and the peak to valley ratio was found equal to 17.7+/-2.7. Comparative measurements of two 3x3x5mm3 CsI:Tl and GAGG:Ce scintillators of same thickness are also presented. All measurements were performed at room temperature ~25 oC, without additional cooling. According to our knowledge this is the first time that the new developed GAGG:Ce scintillator array has been evaluated at low energies. M21-49, Dual-Energy Imaging with an Active Sandwich Detector J. C. Han1, D. W. Kim1, S. Yun1, H. Youn1, S. Yun1, S. Kam1, H. K. Kim1,2 1

Radiation imaging Laboratory, School of Mechanical Engineering, Pusan National University, Busan, Republic of Korea 2 Center for Advanced Medical Engineering Research, Pusan National University, Busan, Republic of Korea

We revisit the doubly-layered detector configuration for dual-energy x-ray imaging. With this sandwich detector, we can obtain motion-artifact-free subtraction images. Using a photodiode array coupled to a phosphor screen and aluminum sheet, we successfully demonstrated the feasibility of the sandwich detector for dual-energy x-ray imaging. We are now constructing the sandwich detector by using two detector modules by stacking them. Designs of the sandwich detector, such as phosphor screen thicknesses and filter material, will be optimized. The imaging performance of the sandwich detector will also be reported by using a quantitative phantom. M21-50, Development of a Ceramic Garnet Scintillator for Positron Emission Tomography S. I. Kwon1, G. Baldoni2, Y. Wang2, M. S. Judenhofer1, Y. Yang1, K. S. Shah2, S. R. Cherry1 1 2

Dept. of Biomedical Engineering, University of California, Davis, Davis, CA, USA Radiation Monitoring Devices, Inc., Watertown, MA, USA

In this study, a novel ceramic garnet scintillator, (GdxLu1-x)3(GayAl1-y)5O12:Ce abbreviated as GLuGAG:Ce, was developed and evaluated. This scintillator has high transparency, high stopping power (attenuation length of 1.3 cm at 511 keV), high light yield (up to ~60,000 ph/Mev), and fast decay time (~40 ns). Because it has a cubic crystal structure, it can be fabricated using ceramic techniques. This allows the material to be made at lower temperatures and more quickly and easily than conventional scintillators grown as single crystals. It also offers possibilities for directly fabricating scintillator elements in the desired size and shape without cutting. Two large volume cylindrical GLuGAG:Ce scintillator specimens were evaluated with different radioactive point sources and on two different PMTs (single channel PMT and 64-channel multi-anode PMT). Sample #1 was 23 mm in diameter and 5 mm in height (volume 2.08 cc) and sample #2 was 24.4 mm in diameter by 15.4 mm in height (volume 7.2 cc). Results were compared with those from an LYSO crystal (10 x 10 x 5 mm3). The photopeak was clearly visible in pulse height spectra from 241 Am, 57Co, 22Na, and 137Cs. The energy resolution and light yield proportionality of 733

GLuGAG:Ce scintillators were comparable with the results of LYSO crystal. Based on initial results, this ceramic garnet scintillator shows promise for γ-ray detection, especially for positron emission tomography (PET). M21-51, Development of a GAGG Depth-of-Interaction (DOI) Block Detector Based on Pulse Shape Analysis S. Yamamoto1, T. Kobayashi1,2, H. Sato3, T. Endo3, Y. Usuki3, K. Kamada4, A. Yoshikawa4,5 1

Nagoya University Graduate School of Medicine, Nagoya, Japan Department of Radiology, Daiyukai General Hospital, Ichinomiya, Japan 3 Furukawa Corporation, Tsukuba, Japan 4 New Industry Creation Hatchery Center (NICHe), Tohoku University, Sendai, Japan 5 Institute for Materials Research (IMR), Tohoku University, Sendai, Japan 2

For developing a high resolution and high sensitivity PET system, depth-of-interaction (DOI) detector is desired. Ce doped Gd3Al2Ga3O12 (GAGG-F) is a promising scintillator for PET applications with high light output with decay time of 92ns. However it was not possible to develop a DOI detector based on pulse shape analysis with GAGG-F. Recently similar scintillator with different Al/Ga ratio, Ce doped Gd3Al3Ga2O12 (GAGG-S), which has decay time of 154ns, was developed. The combination of GAGG-F and GAGG-S will be promising to realize high resolution DOI detectors based on pulse shape analysis. Consequently, we developed and tested a DOI block detector composed of GAGG-F and GAGG-S pixels. Two types of GAGG (GAGG-F and GAGG-S) with 2mm x 2mm x 5mm pixels were combined into 5 x 5 matrix with 0.1mm thick BaSO4 reflector and optically coupled to each other in depth direction to form a 2 layer DOI block. The DOI block was optically coupled to a Si-PM array (Hamamatsu MPPC S11064-050P) with 2mm thick light guide. Two dimensional histogram showed perfect separation with energy resolution of 12.5% for 662keV gamma photons. The pulse shape spectrum showed good separation with peak-to-valley ratio of 8.7. These results indicate that DOI detector with two types of GAGG based on pulse shape analysis is promising for developing a high resolution PET system. M21-52, A Study of a GEM Tracking Detector for Imaging Positrons from PET Radioisotopes in Plants T. Cao1, B. Azmoun2, S. Stoll2, M. L. Purschke2, B. Babst3, P. Vaska1,3, C. L. Woody2 1

Biomedical Engineering, Stony Brook University, Stony Brook, NY, USA Physics Department, Brookhaven National Lab, Upton, NY, USA 3 Bioscience Department, Brookhaven National Lab, Upton, NY, USA 2

Abstract A gas tracking detector is being developed to measure escaping positrons from PET radiotracer isotopes to study the movement and distribution of radiolabelled metabolties in thin plant tissues at high resolution. This device uses a triple GEM detector with a short drift region and an XY strip readout plane to measure a vector for positrons passing through the drift gap. By projecting each particle track back to the object surface, a 2-D image of the spatial distribution of the positrons that escaped from that surface can be reconstructed. This image can be combined with a traditional PET image to improve quantification accuracy in plant imaging experiments using positron emitting tracers. This technique is expected to be an important complement to PET 734

imaging when studying very thin structures such as plant leaves or young seedlings, as well as a potentially stand-alone imaging modality. In this paper, we will describe the current version of our detector system and present results on its performance using various types of phantoms and actual plant specimens. M21-53, A Study on PDP-Based Gas Radiation Detector with Various Electrode Structures S. Eom1, H. Park1, J. Kim1, J. Kang1, H. Lee2, K. Lee2 1 2

Department of Electronics and Electrical Engineering, Dankook University, Yongin-si, Gyeonggi-do, Korea Department of Radiologic Science, Korea University, Seoul, Korea

In this study, a 2-dimensional gas type radiation detector that is based on plasma display technology has been investigated. In the previous studies, four detectors with differing gas mixture were fabricated and its performance was evaluated by measuring the charge density and sensitivity variation due to the applied voltage. In case of the Xe 80%-He 20% mixture yielded the maximum collected charge, which increased from 0.427 μC/cm2 to 1.216 μC/cm2 and its sensitivity varied from 0.116 to 0.246 nC/mRcm2. The sensitivity of the a-Se based detector is about 2 nC/mRcm2 in an electric field of 10 V/μm. The sensitivity of of Xe 80%-He 20% detector is about a tenth lower compared to that of the a-Se detectors, but the applied electric field of the proposed detector is about 1/16 of the a-Se detector. In order to improve the sensitivity of the PDP-based detector, various electrode structures were investigated through simulation and experiment in this study. M21-54, Development of a DAQ Circuit for a Plasma-Display-Panel Based X-Ray Detector H. Lee1, K. Lee1, E. Min1, S. Eom2, H. Park2, J. Kang2 1 2

Dept. of Radiologic Science, Korea University, Seoul, Korea Dept. of Electronics and Electrical Engineering, Dankook, Yongin, Gyeonggi, Korea

The plasma display panel (PDP) is one of the most widely used display components in flat panel displays. It is popular in the TV market due to its relatively simple cell structure, low cost materials, and uncomplicated manufacturing process. Recently, some research groups showed that the cell structure of PDP, which consists of electrodes and gas mixture, could be utilized in the manufacture of radiation detectors. In the previous study, we developed a plasma display panel based x-ray detector (PXD). This prototype detector panel has row and column strips, and it can thus be utilized as an imaging detector. To achieve the 2D x-ray image from the developed panel, a PXD dedicated driving and data acquisition circuit has been developed. The proposed DAQ system consists of a multi-channel high voltage switching board, a multi-channel DAQ board, and an FPGA based control board. The prototype system has a compact design to be easily utilized for various kinds of object imaging experiments. Each of developed module board of the DAQ system has been tested successfully. Now we integrate the individual modules into a system. We hope to further study signal processing to achieve the first x-ray image of PXD. M21-55, Development of a Versatile Wafer-Scale Large-Area CMOS X-ray Flat-Panel Detector S. K. Heo1, J. P. Kosonen1, D. A. Im1, S. J. Lee1, T. W. Kim1, H. K. Kim2

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1 2

R&D center / Sensor Lab, Rayence, Co., Ltd., Hwaseong-si, Gyeonggi-do, Korea School of Mechanical Engineering, Pusan National University, Busan, Korea

It is well known that the complementary metal-oxide-semiconductor (CMOS) x-ray imagers are gaining attention in diagnostic radiology, because of their extremely low noise and high speed readout without image lag due to high electrical charge mobility in single crystalline silicon. Several recent studies have revealed its potential as well as feasibility to diagnostic radiology such as dental cone-beam computed tomography (CBCT), dental intra-oral and digital mammography. The advanced CMOS active pixel design offer advantages of much lower fixed pattern noise and higher signal-to-noise ratio (SNR) compare to x-ray imager in CCDs and amorphous silicon technologies. The active pixel can be realized by adding source follower circuit per pixel. This enables transferring the signal onto a common readout bus as a voltage instead of charge. Various area of diagnostic radiology need different requirement of performance per each application. The CBCT and fluoroscopy which need real-time x-ray imaging emphasize high sensitivity and fast readout rather than high resolution. However, high resolution and low leakage current is the most important performance in the mammography and dental intra oral application. Therefore, CMOS x-ray imager design should be flexible to demands of application. M21-56, X-Ray Imaging with YSO Scintillating Crystal Array M. Kim, J. Lee, I. Park Dept.of physics, SungKyunKwan University, Suwon-si, Korea

We developed an X-ray imager using Yttrium OxyorthoSilicate (Y2SiO5:Ce, YSO) scintillating crystal array and Multi-Anode PhotoMultiplier Tubes (MAPMTs) with the capability of fast X-ray counting and X-ray energy measurement. YSO scintillating crystal array has many advantages. First of all, there is no intrinsic background. We can detect the low energy X-ray photon without internal noise. The X-ray imager consists of detector, readout and readout electronics. The detector consists of 36 YSO scintillating crystal arrays of 88 pixels. This detector is read out by 36 64channel MAPMTs with 36 SPACIROC ASICs in readout electronics. The imager has total 2304 YSO and MAPMT channels that make an array of 4848 pixels. We will present the design and fabrication and performance of the X-ray imager. M21-57, Development of Beam Monitor for Therapeutic Proton Pencil Beam Scanning Mode Using Cherenkov Radiation in Optical Fibers. M. Y. Kim1, D. H. Shin1, S. B. Lee1, Y. K. Lim1, U. J. Hwang2, J. M. Son3, S. G. Kim4 1

Proton Therapy Center, National Cancer Center, Goyang, Korea Department of Radiation Oncology, National Medical Center, Seoul, Korea 3 Department of Bio-convergence Engineering, Korea University, Seoul, Korea 4 Department of Biomedical Engineering, Konkuk University, Chungju, Korea 2

Proton therapy aims to deliver a high dose in a well-defined target volume while sparing the healthy surrounding tissues thanks to their inherent depth dose characteristic (Bragg peak). In proton therapy, several techniques can be used to deliver the dose into the target volume. The one that allows the best conformation with the tumor, is called Pencil Beam Scanning. This method consists in directing lots of small pencil beam into the target in order to cover the 3D volume. The 736

beam position is adjusted in X & Y by 2 scanning magnets while the depth depends on the beam energy. The measurement of the proton beam width and range in the target is very important: real range of proton beams in patients may contain uncertainties on tissue composition, density, organ motions, patient positioning, etc. Due to the lack of national standards and absolute dosimeter in proton dosimetry, we are forced to use relative dosimeters for proton dosimetry. A prototype beam monitor using Cerenkov radiation in optical fibers has been developed for continuous display of the pencil beam status during the therapeutic proton Pencil Beam Scanning mode operation. M21-58, A Time-of-Flight Neutron Activation Method for Measuring Trace Element Concentrations in vivo T. Cao1, S. Mitra2, P. Vaska1,3 1

Biomedical Engineering, Stony Brook University, Stony Brook, NY, USA Sandia National Laboratories, Albuquerque, NM, USA 3 Bioscience Department, Brookhaven National Laboratory, Upton, NY, USA 2

Abstract A time-of-flight neutron activation method is being developed as a technique for measuring trace element concentrations in vivo. This technique is intended to provide concentrations of a range of elements at each voxel of a three-dimensional image. A compact neutron generator produces a mono-energetic neutron and an associated recoil particle in a backto-back fashion. Inelastic neutron scatter from trace element nuclei in the body produces characteristic gamma rays (within ~10E-15s) which are acquired by a gamma spectrometer. The gamma emitting nucleus is identified by the emitted gamma energy. The recoil particle is detected by a position sensitive particle detector, which defines the path of the incident neutron. And the time delay between detecting the recoil particle and the neutron-induced gamma rays is dominated by the neutron time-of-flight, which can be used to determine the location of interaction along the path. Three-dimensional images can be reconstructed to represent the spatial distribution of elements within the sample. A Monte Carlo simulation (Geant4) has been developed and used to investigate the properties of this imaging method including sensitivity, absorbed dose, and spatial resolution. Potential applications are discussed. M21-59, A Convenient Light Guide for Trial Production in Its Optimization Process N. Inadama, Y. Hirano, F. Nishikido, H. Murayama, M. Nitta, T. Yamaya National Institute of Radiological Sciences, Chiba, japan

In this presentation, we introduce a light guide which is advantageous in scintillation detector optimization process at laboratory experiments. In the process, one wants to measure detector performance with gradually changing light guide parameters such as location and length of reflector to be inserted in the light guide. For a light guide, a hard plate like an acrylic plate is generally used. However, it is not easy to make slots in the plates for reflectors to control light spread and it is almost impossible to change, for example, the position of the slots in the same plate. The light guide we propose is made of silicon rubber, RTV rubber. It is known as a coupling material for scintillators because of its transparency and similar refractive index to the scintillators. That is a good character as material of a light guide. To make a light guide of the RTV rubber, what we should do is keep it into favorable shapes until becoming rubbery. Once it became a 737

rubber, we can cut it freely with a cutter or scissors. Reflector insertion process is also easy. The process will be, make a cut into the rubber, bend the rubber to open the part, and set a reflector. Different from an acrylic plate, surfaces of the rubber is a little bit sticky so that the reflector does not move easily. To restore the cut to change its position, one should only put a thin coating of additional RTV rubber in the cut. We also demonstrated advantage of this convenient light guide using the 4-layer DOI PET detector we previously developed. M21-60, Medical Imaging and Non-Destructive Testing with the New LAMBDA Detector F. M. Epple1, D. Pennicard2, S. Smoljanin2, S. Lange2, G. Potdevin1, S. Ehn1, D. Renker1, S. Kaczmarz1, H. Graafsma2, F. Pfeiffer1 1 2

Department of Physics, Tchnical University Munich, 85748, Garching, Germany Photon Science Division, DESY, 22607, Hamburg, Germany

Hybrid pixel detectors are common tools in x-ray imaging. Their energy discrimination, single photon counting ability and high signal-to-noise ratio make these devices useful when an excellent image quality is needed; for example, in medical imaging and non-destructive testing. In imaging techniques that suffer from the polychromatic spectrum of conventional x-ray sources, such as differential phase contrast imaging, these detectors can greatly improve the quality of the images. The Large Area Medipix3 Based Detector Array (LAMBDA) [1] is a photon counting detector developed by the Photon Science Division at DESY (Germany). We have demonstrated its usage in grating based differential phase contrast imaging. This technique uses an x-ray interferometer to measure the strength of attenuation, phase-shift and low angle scattering of x-rays in the specimen [2][3][4]. While this method is fully compatible with conventional x-ray sources, the quality of the images suffers from the broad energy spectrum of such sources [5]. We will show that the image quality can be significantly increased and artifacts that originate from phase wrapping can be corrected if energy discriminating detectors are used. M21-61, Image Science with Photon-Processing Detectors L. Caucci1, A. K. Jha2, L. R. Furenlid1,2, E. W. Clarkson1,2, M. A. Kupinski2, H. H. Barrett1,2 1 2

Department of Medical Imaging, University of Arizona, Tucson, AZ, USA College of Optical Sciences, University of Arizona, Tucson, AZ, USA

We introduce and discuss photon-processing detectors and we compare them with photoncounting detectors. By estimating a relatively small number of attributes for each collected photon, photon-processing detectors may solve a fundamental theoretical problem of any imaging system based on photon-counting detectors, namely null functions. We argue that photon-processing detectors can increase task performance by estimating position, energy, and time of arrival for each collected photon. We introduce a continuous-to-continuous linear operator to relate the object being imaged to the data, and discuss how this operator can be analyzed and inverted analytically to reconstruct the object from the data.

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M22 Image Reconstruction II / Other Imaging Technologies II Friday, Nov. 1 16:30-18:30 Hall B2 Session Chair: Soo-Jin Lee, Paichai University, Dept. of Electronic Engineering, South Korea; Grant Gullberg, Lawrence Berkeley National Laboratory, United States

M22-1, Patient-Specific Optimization of Reconstruction Methods for Dual Isotope Myocardial Perfusion SPECT X. Li1, M. Ghaly1, J. M. Links2, E. C. Frey1 1 2

Department of Radiology, Johns Hopkins University, Baltimore,MD, USA Department of Environmental Health Sciences, Johns Hopkins University, Baltimore,MD, USA

Post-filtered OS-EM and penalized maximum likelihood (PML) using a cross-tracer prior are two potential reconstruction algorithms of interest in dual isotope myocardial perfusion SPECT image reconstruction. Both algorithms require optimization of hyperparameters in order to achieve the best image quality. However, the optimal parameters depend on patient-dependent parameters, including the count level, defect size and orbit. Choosing patient specific optimal OS-EM reconstruction parameters, i.e., the iteration update number and post-filtering cutoff frequency, is also important in our work since we have previously proposed a scheme for obtaining PML parameters based on the resolution properties of the optimal OS-EM images. Doing an exhaustive search for the optimal OS-EM parameters for the three-class classification task is almost impossible, due to the great number of possible combinations of the iteration update number and cutoff frequency of the stress and rest images. We hypothesized that we could divide our phantom population into three groups according to myocardial noise and the ratio of the size of defects to the image resolution in the heart, and optimize the parameters by group (group-wise optimization) for rest and stress images separately using two-class (normal vs. abnormal) Channelized Hotelling observer (CHO) studies. We also obtained the optimal parameters for the whole population (whole-population optimization) for rest and stress images separately. The group-wise optimization method shows significantly better performance than the whole-population optimization method for the two-class classification problem for rest and stress images. Whether this method gives us optimal three-class classification task performance is still under investigation. However, our results showed our group-wise optimization method performs better than a wholepopulation optimization method in the three-class classification task for dual isotope myocardial perfusion SPECT. M22-2, Influence of MRI Artifacts on PET Image Reconstruction Using MRI-Based Priors L. L. Caldeira1, J. Scheins1, P. Almeida2, H. Herzog1 1 2

Institute of Neuroscience and Medicine, Forschungszentrum Juelich, Juelich, Germany Instituto de Biofisica e Engenharia Biomedica, Science Faculty of University of Lisbon, Lisboa, Portugal

MRI information can be used to improve PET images by using MAP reconstruction algorithms. The aim of this study is to assess the influence of MRI image quality using two different methods 739

to incorporate MRI information (the boundaries and the Bowsher method). MRI simulated data with different noise and intensity inhomogeneity levels are used. PET data are also simulated to assess the performance of reconstruction. MAP algorithms using MRI information improve PET image quality, but the MRI image quality clearly influences this improvement. The Bowsher and boundaries methods are robust to noise and intensity inhomogeneity, if the MRI artifacts are acceptable. The Bowsher method achieves lower figures of merit, but it is more sensitive to noise and intensity inhomogeneity. M22-3, Evaluation of Reconstruction-Based Compensation for Imaging Degrading Factors in I123 FP-CIT Brain SPECT Y. Du, N. Anizan, Y. Dong, Z. Szabo, M. Lodge, E. C. Frey Radiology, Johns Hopkins Medical Institutions, Baltimore, MD, USA

I-123 FP-CIT SPECT imaging of the dopaminergic system is used to confirm the diagnosis of Parkinsons disease (PD) and differentiate PD from essential tremor. Semi-quantitative analysis of striatal binding potential (BP) has been used for confirming diagnosis and quantitative monitoring of disease progression. Conventional clinical SPECT reconstruction methods do not compensate for many image degrading factors. This can decrease the reliability of BP estimates and lead to incorrect diagnosis. Here, we evaluated the effects of different iterative reconstruction based compensations for degrading factors in I-123 brain SPECT. Various striatal compartments in a brain phantom were filled with I-123 solution having various activity concentration: the right caudate and putamen mimicked a normal BP and the left caudate and putamen mimicked PD with a reduced BP. Projections were acquired using Siemens Symbia SPECT/CT system with a LEHR collimator. The images were reconstructed using the iterative OS-EM algorithm with different combinations of reconstruction based compensation for various degrading factors, including attenuation, detector response, collimator septal penetration and scatter, object scatter, and downscatter of I-123 high-energy photons. Images were also reconstructed using OS-EM with no compensation and filtered backprojection. BP in each striatal compartment was then computed. Results showed improved contrast and resolution of images obtained with compensations for more degrading factors than those with less. The best results were obtained for images reconstructed with compensations for all degrading factors. Quantitative results followed the same trend as image quality with full compensation giving the smallest errors. Residual partial volume effects still caused substantial underestimation. In conclusion, it is important to compensate for all image degrading factors in I-123 brain SPECT. Further improvements in accuracy require partial volume compensation. M22-4, Influence of Three Reconstruction Algorithms on the Estimation of Standardized Uptake Values E. Grecchi1, K. Thielemans1,2, G. Cook1, C. Tsoumpas1 1 2

Division of Imaging Sciences and Biomedical Engineering, King's College London, London, UK Institute of Nuclear Medicine, University College London, London, UK

In clinical practice accurate and precise quantification of PET images is of crucial importance especially for tumor staging when comparing pre- and post- treatment scans. For example a 740

change in the standardized uptake values (SUV) of 10-20% can discriminate whether a treatment is effective or not. However, several factors cause degradation of the accuracy and precision of quantitative information. Iterative reconstruction methods can help towards more accurate tumour delineation and potentially quantification. However, the most commonly used reconstruction technique (Ordered Subset Expectation Maximization, OSEM) has pitfalls that are critical for quantification: bias (e.g. at early iterations and at low count statistics) and noise (e.g. at late iterations). The aim of this work is to evaluate the quantitative performance of existing reconstruction algorithms with acquired phantom data and PET/CT (18F-fluoride and 11Ccholine) scans of patients with metastatic prostate cancer. Data are reconstructed with three different ordered subset (OS) methods: OSEM, OS Maximum A Posteriori One Step Late (OSMAPOSL) and OS Separable Paraboloidal Surrogate (OSSPS). These three algorithms are available with the open source Software for Tomographic Image Reconstruction (STIR, http://stir.sf.net). We investigate the SUVmax and SUVmean for each of the three reconstruction methods and how they change over subiteration. Our findings show that the limit cycle behavior of OSEM and OSMAPOSL may cause important variability on the SUV estimations questioning their clinical applicability. In contrast, the OSSPS algorithm shows encouraging performance in term of stability over iterations. M22-5, Fast, Robust Dynamic Field-of-View Adjustment for Iterative Reconstruction of Dedicated Breast CT Images I. Reiser1, E. Y. Sidky1, R. M. Nishikawa1, K. Yang2, J. M. Boone2, X. Pan1 1 2

Radiology, University of Chicago, Chicago, IL, US Radiology and Biomedical Engineering, University of California at Davis, Sacramento, CA, US

Dedicated breast CT (bCT) is a novel modality for breast imaging that is undergoing clinical testing. To date, several hundred patients have been imaged with bCT. The appeal of bCT is its capability to visualize the complex 3D breast anatomy. A potential clinical application of bCT imaging is breast cancer screening, which requires low radiation dose and high resolution. Iterative image reconstruction (IIR) algorithms can alleviate the impact of data noise, and are therefore promising for reconstructing low-dose CT. However, IIR methods are implicit, thus, partial reconstruction of the object is not possible and incomplete coverage of the object by the reconstruction field-of-view (FOV) results in artifacts. Thus, the purpose of this work was to make IIR practical for reconstructing high-resolution bCT by aligning the reconstruction FOV with the actual breast, rather than to reconstruct the entire scanner FOV. To be practical for patient imaging, FOV-adjustment needs to be performed in an automated manner and be robust against variation in breast size and patient positioning. This study used 15 patient images acquired on a dedicated cone-beam breast CT. Location and size of the actual breast within the scanner FOV was determined from two projection views at 90 and 180 degrees, aligned with the reconstruction grid directions perpendicular to the axis of rotation. In each projection view, the lateral boundaries of the projected breast were identified and served as bounding boxes for the reconstructed image array. The resulting image volume was reduced in size, and, depending on patient positioning, could also be shifted off-center. Adjusting the reconstruction FOV reduced computation time by 30%-40%, depending on breast size. For all 15 patients, the reconstruction FOV completely and tightly covered the breast, indicating robustness of the algorithm. In conclusion, this method may alleviate some of the computational burden of IIR.

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M22-6, Iterative Image Reconstruction from Low-Dose Patient Breast CT Data J. Bian1, K. Yang2, E. Sidky1, J. Boone2, X. Pan1 1 2

Department of Radiology, The University of Chicago, Chicago, IL, US Department of Radiology, University of California at Davis, Sacramento, CA, US

Dedicated breast CT scanners for 3D imaging of the breast are under active investigation and development. Current dedicated breast-CT prototypes are based on flat-panel detectors and generally adopt a circular cone-beam imaging configuration with breasts being pendant through an opening in table top, and analytic-based algorithms such as the FDK algorithm are currently used for image reconstruction. Because the total imaging dose delivered to the patient in a breast-CT scan remains about the same as that in a typical two-view mammography exam, the use of a large number of densely sampled views required by analytic-based algorithmss can lead to projection data and images of low SNR. Moreover, both normal and cancerous tissues of a breast have attenuation properties similar to that of water, and glandular tissues in a breast generally have very fine structures. Micro-calcification, another important imaging subject in breast imaging, also require fine spatial resolution. Low contrast, fine structure, and low-SNR projection data thus makes reconstruction improvement from low-dose dedicated breast-CT data challenging. Optimization-based (i.e. iterative) image reconstruction algorithms have been considerably investigated and developed for low-dose cone-beam CT (CBCT). In the work, we investigat optimization-based image reconstruction from low-SNR patient-breast-CT data. Both qualitative and quantitative characterizing studies on image quality has been performed. The results suggest that optimization-based algorithms may improve image quality for current dedicated breast CT. M22-7, Time Reconstruction Study Using Tubes of Response Backprojectors in List Mode Algorithms, Applied to Breast PET Based on Monolithic Crystals L. Moliner1, A. Gonzalez1, C. Corracher2, P. Conde1, P. Bellido1, E. Crespo1, L. Hernandez1, A. Iborra1, J. P. Rigla1, M. J. Rodriguez-Alvarez1, F. Sanchez1, M. Seimetz1, A. Soriano1, L. F. Vidal1, J. M. Benlloch1 1 2

I3M, Institute of Instrumentation for Molecular Imaging, Valencia, Spain Oncovision, GEM Imaging SA, Valencia, Valencia

In this work, a study on the reconstruction times for three different reconstruction algorithms namely, MLEM, List Mode (LM)-MLEM and LM-OS is shown. These algorithms have been implemented in the MAMMI prototype, a dedicated breast PET. One of the fundamental goals in the PET reconstruction process is to achieve an accurate diagnosis in a brief period of time. LM algorithms update the voxels values for each recorded line of response (LOR) instead of updating the complete image as is the case in the standard algorithms like MLEM or OSEM. The LM algorithms usually calculate the weight of the pair voxel-LOR on-the-fly without the need of a storage system matrix containing that information. The algorithms used in this comparison have been implemented following a parallel code structure in order to take advantage of the latest computational multi-core architectures. In this work, a dual Intel Xeon processor computer with four cores each of them and 12GB RAM memory was used. All the coding has been implemented in 64 bits. In addition to the timing study, we compare the image quality of the images provided by the algorithm implemented in the scanner. The time results show that the MLEM algorithm has a computational cost of about 750 seconds, almost independent of the number of coincidences recorded. The performance of the LM algorithms depended on the backprojector method used. Our 742

initial results show that the LM algorithms can process up to 200 kCoincidences per second when using the TOR backprojector and up to 600 kCoincidences per second for the Siddon backprojector. The best timing performance is achieved with LM-OS-Siddon although the LMMLEM-TOR reconstruction provides a better imaging quality performance. Therefore, the best trade-off is achieved with the LM-MLEM-TOR which even allows a real-time PET reconstruction for routinely acquisitions with the MAMMI prototype. M22-8, Verifying Cone-Beam CT Extended Axial Coverage with Iterative Reconstruction Using Real Data A. M. Davis, E. A. Pearson, C. A. Pelizzari, X. Pan Department of Radiology, University of Chicago, Chicago, IL, USA

Cone-beam CT imaging devices have an axial coverage that is limited by the detector size. We previously found in simulation studies that the useful axial coverage could be extended by using two circular scans at different axial positions. By combining this dual scan with iterative reconstruction techniques, we can increase the useful field of view while providing better image quality in the region between the two circles. Here we experimentally test our previous simulation studies with real phantom scan data. M22-9, Investigation on Scale-Based Neighborhoods in MRFs for Statistical Iterative CT Reconstruction H. Zhang1, Y. Liu1, J. Wang2, J. Ma1,3, H. Han1, Z. Liang1 1

Stony Brook University, Stony Brook, NY, USA University of Texas Southwestern Medical Center, Texas, TX, USA 3 Southern Medical University, Guangzhou, China 2

Statistical iterative reconstruction (SIR) algorithms have shown advantages over conventional filtered backprojection (FBP) for low-dose X-ray CT reconstruction. For the SIR algorithms, the regularization (penalty) term which reflects a prior information plays a critical role on the algorithm performance. One commonly used regularization term is the quadratic-form Gaussian Markov random field (MRF), which penalizes differences among neighboring voxels in a small fixed window without considering discontinuities in images, thus may lead to over smoothing of edges or fine structures. In this work, we presented a quadratic-form MRF regularization with varying window size determined by the object scale, which is a descriptor of the image uniformity. For a uniform region (scale is large), a larger MRF window is adopted because the coupling between current pixel and its neighbors is strong; while for the interface (scale is small), a smaller MRF window is employed since the coupling between current pixel and its neighbors is weak. This novel regularization term was incorporated into our penalized weighted least-squares (PWLS) iterative reconstruction scheme to improve low-dose CT reconstruction. Simulation results with a Shepp-Logan phantom revealed the presented regularization term is superior to the conventional Gaussian MRF and comparable to the popular total variation(TV) regularization in terms of noise suppression and edge preservation. Further quantitative evaluations are still under progress.

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M22-10, Impact of the Depth of Interaction in Reconstruction of Small-Animal SPECT Data Acquired with a Space-Variable-Focusing Collimator D. Benoit1, S. Matrejean2, F. Mathy3, G. Montemont3, I. Buvat1 1

QIM IMNC-IN2P3/CNRS, ORSAY, FRANCE Biospace Lab, PARIS, FRANCE 3 CEA LETI, GRENOBLE, FRANCE 2

In SPECT imaging, the collimator is a key component that determines spatial resolution and sensitivity. Many types of collimators have been designed as a function of the targeted application. We recently proposed a spatially-variable-focusing cone-beam (SVFCB) collimator that can be used to improve the sensitivity compared to a parallel-beam collimator while reducing the truncation problem associated with fan-beam collimation. Based on Monte Carlo simulations, we designed the SVFCB collimator so that the shortest focal length was within the field of view (FOV). We studied the impact of the ray-tracing projector used in the forward projection and the improvement of image quality brought by modeling the point spread function (PSF) or the depth of interaction (DOI) effect in the reconstruction process. Results show that the projector model had a large impact on the resulting image quality. A sophisticated projector and the use of a PSF model improved the spatial resolution from 1.7 mm to 1.35 mm compared to a simple Siddon projector without PSF or DOI model. Yet, modeling the PSF or the DOI introduced Gibbs phenomenon at high number of iterations that will have to be compensated to avoid misleading quantification. M22-11, Image Reconstruction of Rectangular PET Ssystems Using Distance-Driven Projections H. Qian, R. M. Manjeshwar GE Global Research, Niskayuna, NY, USA

Rectangular geometry is one of preferred choice in design of Positron Emission Mammography because of its potential for both high sensitivity and high resolution. The irregular radial and angular sampling in the rectangular geometry presents great challenge to system matrix generation and image reconstruction. Distance-driven projectors had been successfully applied in ring geometry to model the uneven spacing of the sinogram due to the ring curvature as well as the gaps resulting from the block structure of the scanner. We modified the distance-driven projections for rectangular geometry and combine the system matrix generation into the iterative image reconstruction process. While distance-driven projections are most efficient in image reconstruction when histogram bins are accessed in special order, the system matrix generation method introduced in this presentation can also been used in list-mode reconstruction. M22-12, Modeling of Pixelated Detector in SPECT Pinhole Reconstruction B. Feng Preclinical Solutions, Siemens Medical Solutions USA, Knoxville, TN, USA

A challenge for the pixelated detector is that the detector response of a gamma-ray photon varies with the incident angle and the incident location within a crystal. The normalization map obtained 744

by measuring the flood of a point-source at a large distance can lead to artifacts in reconstructed images. In this work, we investigated a method of generating normalization maps by ray-tracing through the pixelated detector based on the imaging geometry and the photo-peak energy for the specific isotope. The normalization is defined for each pinhole as the normalized detector response for a point-source placed at the focal point of the pinhole. Ray-tracing is used to the ideal flood image for a point-source. Each crystal pitch area on the back of the detector is divided into 60 x 60 sub-pixels. Lines are obtained by connecting between a point-source and the centers of sub-pixels inside each crystal pitch area. For each line ray-tracing starts from the entrance point at the detector face and ends at the center of a sub-pixel on the back of the detector. Only the attenuation by NaI (Tl) crystals along each ray is assumed to contribute to the flood image. The attenuation by the silica (SiO2) reflector is also included in the ray-tracing. To calculate the normalization for a pinhole, we need to calculate the ideal flood for a point-source at 360 mm distance where the point-source was placed for the flood measurement and the ideal flood image for the point-source at the pinhole focal point. From the ideal flood image for the point-source at the pinhole focal point, we can calculate the normalization for the pinhole by multiplying times the crystal efficiencies and scaling by the incoming flood strength image (68 x 68). The normalizations are incorporated in the iterative OSEM reconstruction as a component of the projection matrix. Applications to single-pinhole and multi-pinhole imaging show that this method greatly reduced the reconstruction artifacts. M22-13, Impact of TOF Information in OpenPET Imaging H. Tashima, T. Yamaya Molecular Imaging Center, National Institute of Radiological Siences, Chiba, Japan

We are developing an open-type PET geometry that we named OpenPET. One possible geometry is the dual-ring OpenPET, which consists of two detector rings separated by a gap for entrance of the radiation beam. The gap can also be used for different modalities such as X-ray CT to realize a simultaneous multi-modality system. In addition, the dual-ring OpenPET has an effect to enlarge the axial field-of-view. In our previous simulations and experiments the OpenPET imaging geometry was shown to be feasible by applying iterative reconstruction methods. However, the gap violates Orlovs completeness condition for accurate tomographic reconstruction. Therefore, the gap could lead to artifacts caused by lost low-frequency components in the projection data depending on the shapes of imaging subjects. In this study, we investigate the effect of time-offlight (TOF) information, which is expected to compensate for the lost low-frequency components in OpenPET imaging. We simulated the dual-ring OpenPET geometry with a numerical phantom and analyzed frequency components of the reconstructed images. The result showed that the lowfrequency components were not fully estimated in the gap region of the dual-ring OpenPET while those components were well recovered with the TOF information. M22-14, Dose Reduction Achieved by Dynamically Collimating the Redundant Rays in FanBeam and Cone-Beam CT Y. Xia1,2, M. Berger2,3, C. Riess2,3, J. Hornegger1,2, A. Maier1 1

Pattern Recognition Lab (LME), Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany Erlangen Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander-University ErlangenNuremberg, Erlangen, Germany 2

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Research Training Group "Heterogeneous Image Systems", Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany

In X-ray computed tomography (CT), fan-beam data from projections acquired over a range of π plus the fan angle is sufficient for reconstruction. Such a projection interval is referred to as shortscan and is widely used to reduce acquisition time and radiation dose. However, a short-scan measures data once in some views while twice in other views. Traditionally, the redundant data are weighted by a smooth function (e.g. the Parker weight) before filtering. In this paper, we present an algorithmic setup that employs dynamic collimation to shield the redundant rays and propose two algorithms to correct the resulting truncation. This approach is able to potentially decrease the dose in a short-scan while retaining good image quality. M22-15, Optimizing Image Reconstruction for Clustered Pinhole PET M. C. Goorden1, F. van der Have1,2,3, F. J. Beekman1,2,3 1

Radiation Detection & Medical Imaging, Delft University of Technology, Delft, Netherlands Image Sciences Institute and Rudolf Magnus Institute, University Medical Center Utrecht, Utrecht, Netherlands 3 Molecular Imaging Laboratories, Utrecht, Netherlands 2

A newly developed Versatile Emission Computed Tomography system (VECTor) enables simultaneous imaging of SPECT and PET tracer molecule distributions at sub-mm resolutions in mice. VECTor uses a dedicated collimator with clusters of small opening-angle pinholes that is mounted on a SPECT system with large-area stationary NaI detectors. The higher energy (511keV) of annihilation gamma photons resulting from PET tracer decay compared to gamma photons emitted by SPECT tracers (typically 140 keV) requires for a new evaluation of image reconstruction software instead of only slightly adapting standard SPECT methods. The preliminary results presented here demonstrate that such a reconstruction optimization strongly improves VECTors performance for imaging PET tracers. We investigated how several improvements of the gamma photon transport models on which image reconstruction is based affected reconstructed phantom images. We tested (i) incorporating gamma photon paths that go through multiple pinholes (multiple-pinhole paths), (ii) accurately modeling the variable depth-ofinteraction (DOI) in the NaI gamma detector, and (iii) including larger portions of the tails of the point spread functions (PSFs). Reconstructed images of a syringe filled with 18F-solution were most uniform when multiple-pinhole paths, DOI and a large part of the PSF tails were modeled. The effect of PSF tail modeling was most pronounced; including gamma photons that have a chance 1 cm and > 93% for sphere diameter < 1 cm. The method resulted operator-independent (between operator variation coefficient < 10%) and feasible, resulting in a full consistency between the procedure to calibrate the method and the procedure to apply the method to the MTV segmentation on real 18F-FDG PET patient images. M23-25, Equivalent Al Based Energy Weighting Imaging with a Photon Counting X-Ray Detector Y.-N. Choi, S. Lee, H.-J. Kim Department of Radiological Science, Yonsei unversity, Wonju, Korea

Energy weighting imaging with a photon counting X-ray detector (PCXD) can improve the contrast-to-noise ratio (CNR) and/or signal-to-noise ratio (SNR) compared to the charge integrating detector [1], [2]. However, energy weighting imaging with PCXD has a limitation as follows: to calculate energy weighting factors for energy weighting imaging, we should know the type of the contrast and background materials, their thicknesses, and the attenuation coefficients. Therefore, improved methods to calculate energy weighting factors are needed. To address this issue, we proposed an improved calculation for energy weighting factors in spectral X-ray images. For our new energy weighting imaging, we found the equivalent Al thicknesses: the number of detected photons passing through the equivalent Al thicknesses to be identical to those passing through the target object. Then, weighting factor can be calculated by using the linear attenuation coefficients of the Al and equivalent Al thicknesses. For this study, we used a validated Monte Carlo simulation tool, Geant4 Application for Tomographic Emission (GATE) version 6.0. The effect of our energy weighting method on image quality was evaluated using a cylindrical phantom composed of PMMA with a height of 30 mm and diameter of 25 mm. CaCO3, iodine, and adipose with diameters of 4.0 mm inserted into the PMMA cylinder were used as contrast materials. The densities of the CaCO3, iodine, and adipose were 2.83, 0.05, and 0.95 g/cm3, respectively. We have shown that energy weighting factors and image quality of the energy weighting images obtained from our new method is similar to that obtained from conventional energy weighting method. M23-26, Automatic alignment and registration for PET/CT reconstructions by the crosscorrelation maximization method Y. Zhang, H. Baghaei, H. Li, R. Ramirez, W.-H. Wong Department of Cancer Systems Imaging, University of Texas MD Anderson Cancer Center, Houston, Texas, USA

The images from PET/CT system need to be registered and fused for diagnosis and treatment, which require the alignment and calibration of the PET and CT geometries. For commercial PET/CT systems, the alignment of the PET and CT are assured by mechanical precision during the manufacturing, assembling and the installation process, followed by another calibration alignment with special designed tools, phantoms and procedures. And such phantom calibration process needs to be repeated during the routine operation regularly. The alignment parameters usually are 778

stored in each system and are used for each scan, which are very important for image registration and fusion, as well as the attenuation and scattering correction for PET images. However, due to the complication in real situations such as the patient bed sagging and patient moving, a perfect alignment may not always be achievable. In this study, we developed an automatic alignment technique from real PET and CT reconstructions by the maximization of the cross-correlation between the PET and CT images. The new method can generate the alignment matrix of the 3 translation and 3 rotation transformation parameters automatically. Since the parameters are derived from the real images, no point-like or line-like specially designed phantoms are used; therefore the alignment can be achieved from real objects themselves. With this method, the high accuracy alignment of the PET and CT gantries and the regular re-calibration process are no longer necessary. Moreover, complications in real situation mentioned above can be corrected by this automatic method. An iterative produce based three 2D cross-correlation are developed; the PET and CT images of a mouse from the MuPET/CT system are tested with this method and good alignment results are achieved. M23-27, Sinogram Restoration of Anode Angle Effects in Helical Cone-Beam CT K. J. Little, P. J. La Riviere Dept. Radiology, University of Chicago, Chicago, IL, USA

A rotating anode made of a high-atomic-number material such as tungsten is usually a core component of modern X-ray tubes. Incident electrons impinge on the anode and result in X-rays due to bremsstrahlung radiative losses and the emission of characteristic X-rays. Nonradiative (heat) energy is also generated in large amounts in these interactions, and the rotation of the anode allows for the dissipation of this energy over a larger area. In order to dissipate this nonradiative energy over an even greater area, the edge of the anode known as the focal track is generally a beveled edge with a small angle (typically 5-7 in a CT tube). While a comparatively larger area of the focal track is exposed to electrons, the small size of the effective projected focal spot is maintained due to the line-focus principle. The line-focus principle works well for the central detector channels, but not all detectors see the same projection of the rectangular, angled focal spot. Due to the anode angulation, a more peripheral detector sees a larger effective focal spot size than a central detector. This anode angle effect has been shown to degrade peripheral resolution in some cases, and sinogram restoration methods for compensating for the resulting blurring have been proposed by our group. In earlier works, however, the correction for the resolution nonuniformities caused by anode angulation was performed only for a 2D circular geometry. While sinogram restoration has been applied to cone-beam geometry and with a dual focal spot, a correction for the finite, angled anode has not yet been made for a 3D geometry. The purpose of this current work is to expand the anode angle correction method to the 3D helical cone-beam geometry. We do this by modeling the attenuation lines that contribute to the averaged measurement made at each sinogram location, with the goal of incorporating our modeled blurring into penalized-likelihood sinogram restoration. M23-28, 1-D Interpolation Method for the HRRT PET Sinogram Gap-Filling S. Peltonen, U. Tuna, U. Ruotsalainen Department of Signal Processing, Tampere University of Technology, Tampere, Finland

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The ECAT High Resolution Research Tomograph (HRRT) (CTI PET Systems, Knoxville, TN, USA) is a positron emission tomography (PET) scanner producing PET sinogram data with gaps. These gaps are areas of nonexisting sinogram data formed due to the physical limitations of the HRRT scanner detector block configuration. We present a simple non-interative and fast 1-D cubic convolution based interpolation scheme to fill the gaps of the data. The scheme is based on the idea of shrinking and resizing of previously introduced gap-filling by using the slices in the direction of the radial samples. This method shrinks the data by taking the gaps away, resizes it by bicubic interpolation back to the original size and fills the gaps by the resized data. The new scheme is a symmetric version of it using 1-D cubic interpolation and has a scaling parameter for adjusting the range of samples influencing the result. M23-29, Kinetic Modeling of 18F-FMISO in Glioblastoma M. Bentourkia1, F. Lamare2, M. Allard2, P. Fernandez2 1 2

Nuclear Medicine and Radiobiology, Université de Sherbrooke, Sherbrooke, Canada Service de Mdecine Nuclaire, Universit de Bordeaux2- EPHE, Bordeaux, France

Glioblastomas (GBM) are brain tumors that have rapid proliferation and increased neovasculature. They account for 54% of all gliomas. The tumor develops till it provokes the reduction of the blood supply resulting in hypoxia (i.e. reduction of partial pressure of oxygen). In this work, we report the kinetic modeling of human GBM measured with positron emission tomography (PET) and 18F-fluoromisonidazole (FMISO) radiotracer. The concentration of FMISO in tissue equilibrates with that of FMISO in plasma after 30 min, while FMISO can be trapped in hypoxic tissues for more than 2 h. Although FMISO has been used for several years, still it has no appropriate pharmacokinetic model universally recognized. We used in this work the compartmental kinetic modeling at the pixel level for two- and three-compartments, with and without the rate constant k4, and explored the difference by adding a later frame at 2h and 4h. The calculated parametric images of the distribution volume showed a difference against the perfusion K1. These two parametric images appear resembling to those acquired at 4h and at 15 min respectively. There were a significant correlation between distribution volumes obtained with the extra frames at 2h and 4h. On the other hand, the two-compartment model and the threecompartment model without k4 did not satisfactorily fit the data. In conclusion, FMISO behaves differently in hypoxic tumors than in perfused tumors and normal tissues, therefore appropriate kinetic modeling should be applied depending on these characteristics. It appears then mandatory to discriminate hypoxic from perfused tissues to conduct appropriate radiotherapy treatment. Spectral analysis could be a safe tool to fulfill this requirement. We have observed hypoxia in the images by means of kinetic modeling but the determination of the hypoxia by means of tumor to blood ratio was not always accurate. M23-30, Impact of Motion on Indirect and Direct Estimation of Kinetic Parameters from Dynamic PET Data F. A. Kotasidis1,2, C. Tsoumpas3, G. I. Angelis4, J. C. Matthews2, A. J. Reader5, H. Zaidi1,6 1

Division of Nuclear Medicine & Molecular Imaging, Geneva University Hospital, Geneva, Switzerland Wolfson Molecular Imaging Centre, MAHSC, University of Manchester, Manchester, United Kingdom 3 Division of Imaging Sciences & Biomedical Engineering, King's College London, London, United Kingdom 4 Brain and Mind Institute, University of Sydney, Sydney, Australia 2

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Montreal Neurological Institute, McGill University, Montreal, Canada Geneva Neuroscience Centre, Geneva University, Geneva, Switzerland

Clinical PET imaging of the abdomen and thorax rely on the use of standardised uptake value index derived from static imaging, but improved quantification can be performed using dynamic protocols and estimating kinetic parameters from the dynamic PET data. However, quantitative parameters derived from both static and dynamic imaging protocols suffer from patient motion. In dynamic imaging, the motion-induced data blurring and emission-attenuation mismatch results in erroneous time-activity curves potentially leading to erroneous parametric maps. Furthermore, the effects of motion on direct parameter estimates using 4D image reconstruction algorithms are relatively unknown. In this work, we evaluate the impact of body motion on kinetic parameters in dynamic abdominal and thoracic PET imaging using a novel 5-D numerical body phantom. Furthermore, we compared parameter estimates obtained using both conventional postreconstruction analysis, as well as direct 4D image reconstruction. Motion-induced data blurring was found to affect kinetic parameters especially at the boundaries of regions. No significant difference in bias was found between the 2 kinetic parameter estimation methods. Further work is underway to include inter-frame motion such as patient voluntary motion. M23-31, Do Scatter and Random Corrections Affect the Errors in Kinetic Parameters in Dynamic PET? - A Monte Carlo Study I. Häggström1, A. Larsson1, C. R. Schmidtlein2, M. Karlsson1 1 2

Dept. of radiation sciences, Umeå University, Umeå, Sweden Dept. of medical physics, Memorial Sloan-Kettering Cancer Center, New York, USA

Background: Dynamic positron emission tomography (PET) data can be evaluated by compartmental models, yielding model specific kinetic parameters. Knowledge and management of errors and uncertainties associated with the parameters are however crucial for them to be of quantitative use. Scattered and random coincidences seriously degrade the PET image quality if not corrected for properly, and that effect on the kinetic parameters is not well investigated. Aim: To investigate the effects of corrections for random and scattered coincidences on kinetic parameters from two Monte Carlo (MC) simulated dynamic PET scans. Method: The MC software GATE was used to simulate two dynamic PET scans of a phantom containing three regions; blood, tissue and a static background. The two sets of time-activitycurves (TACs) used were generated for a 3-compartment model with preset parameter values (K1, k2, k3, k4 and Va). The PET data was reconstructed into 19 frames by both ordered-subset expectation maximization (OSEM) and filtered back-projection (FBP) with normalization and additional corrections C (A=attenuation, R=random, S=scatter): Trues (AC), prompts (ARSC), trues+scatters (ASC) and trues+randoms (ARC). SC and RC were performed using additive sinograms in OSEM and precorrections in FBP. Kinetic parameters were obtained by weighted non-linear-least-squares fitting of TACs from the tissue and blood regions. Results: The bias was small for K1 (