Artifacts in

Artifacts in Digital Radiography (DDR & CR) Ivan Kwok Rad II POH

What is Digital Radiography? 

DR???

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Digital detectors with computer processing are used instead of traditional film-screen combination

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Computed radiography

Computed Radiography 

CR

What is Digital Radiography? 

Digital x-ray sensors are used instead of traditional film-screen combination

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Computed radiography

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Direct-capture digital radiography (DDR)

Direct-capture Digital Radiography 

DDR

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The detector directly connect with the computer

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No intermediate mechanical step to read out the information from the detector

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Normally called as DR

Direct-capture Digital Radiography 

Two types of DDR ◦ Indirect DDR

◦ Direct DDR

Indirect DDR vs Direct DDR 

Direct ◦ X-ray directly to be electronic signal

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Indirect ◦ X-ray interacts to be light photon, then converts into electronic signal

What is ARTIFACT? 

Feature in an image that masks or mimics a clinical feature, impairs image quality, or obscures abnormalities.

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e.g. : Motion unsharpness, over / under exposure

CR Artifact

CR Artifact 

Broadly classified into two types ◦ Image acquisition artifacts

◦ Image processing artifacts

Image acquisition artifact

Image acquisition artifact 

Twin artifact (double exposure) ◦ Cause  Two subsequent exposure on same imaging plate

◦ Appearance  Two images appear in same ‘image’

◦ Solution  Proper use of x-ray equipment

Image acquisition artifact 

Twin artifact (double exposure)

Image acquisition artifact 

Twin artifact (double exposure)

Chest radiography shows double exposure due to IP unloading

Image acquisition artifact 

Uncollimated image ◦ Cause  Improper collimation

◦ Appearance  Unsharp image

◦ Solution  Proper collimation in accordance with cassette size and body part

Image acquisition artifact 

Uncollimated image

Image acquisition artifact 

Delay scanning ◦ Cause  Delayed between acquisition and processing of image

◦ Appearance  Fading of image

◦ Solution  Proper knowledge of radiographers to check that no delay between acquisition and processing.

Image acquisition artifact 

Delay scanning

Image acquisition artifact 

Exposure through back of cassette ◦ Cause  Poor basic knowledge of construction of cassette

◦ Appearance  Various patterns according to cassette design

◦ Solution  Re-education of radiographer in handling of cassettes

Image acquisition artifact 

Exposure through back of cassette

Image acquisition artifact 

Over-exposure ◦ Cause  Improper exposure setting

◦ Appearance  Darkening of image

◦ Solution  Proper exposure factors set

Image acquisition artifact 

Over-exposure

Image acquisition artifact 

Under-exposure ◦ Cause  Improper exposure setting

◦ Appearance  Grainy image due to quantum mottle

◦ Solution  Proper exposure factors set

Image acquisition artifact 

Under-exposure

Image acquisition artifact 

Under-exposure

Image acquisition artifact Under-exposure?

NO!

Image acquisition artifact 

Flipping Imaging plate ◦ Cause  Back side of IP is flipped as front side

◦ Appearance  moire pattern, very grainy

◦ Solution  Put the IP back into proper position

Image acquisition artifact 

Improper grid usage ◦ Cause  Usage of grid with low grid frequencies

◦ Appearance  Different types of moire pattern

◦ Solution  Use grid with higher grid frequencies  Grid lines should run perpendicular to plate reader’s laser scan lines

Image acquisition artifact 

Improper grid usage

Image acquisition artifact 

Improper grid usage

Visible vertical grid line due to orientation of grid line parallel to the plate reader’s scan lines

Image acquisition artifact 

Scatter radiation ◦ Cause  Un-use cassettes placed too close the primary beam  No erasure of long storage un-use cassettes

◦ Appearance  Degrade of image quality  Imprint of objects placed over the cassettes

◦ Solution  Protect cassette from any unwanted radiation  Erase cassette before using

Image acquisition artifact 

Scatter radiation

A pen was put on the cassette without any shielding for some time

Image acquisition artifact 

Scatter radiation No erasure of long storage cassette. The cassette was put in the examination room for a long period without used nor erasure.

Image acquisition artifact 

Kink artifact ◦ Cause  Mishandling of imagig plate during cleaning process

◦ Appearance  Kink mark(s) on the image

◦ Solution  Handle the cassettes and image plate with care

Image acquisition artifact 

Kink artifact IVU image with kink mark (upper arrow), which can be mis-diagnosed as contrast extravasation.

Other kink marks (middle and lower arrow) can be mistaken as calculi.

Image acquisition artifact 

Light blub effect ◦ Cause  Under high exposure, back scattered radiation entering the IP from the patient’s bed

◦ Appearance  Darkening of lower and outer portions of image

◦ Solution  Reduce back scatter by lowering the kV, proper collimation, or use grid

Image acquisition artifact 

Light blub effect

Image processing artifact

Image processing artifact 

Crack(s) on imaging plate ◦ Cause  Damaged IP due to frequent unloading

◦ Appearance  Crack(s)

◦ Solution  Change the cracked IP

Image processing artifact 

Crack(s) on imaging plate

Image processing artifact 

Dust on imaging plate ◦ Cause  Dust particles stuck over the IP

◦ Appearance  Focal radiopacities

◦ Solution  Regular cleaning of IP with proper cleaner (ethyl-alcohol) and cloth (lint-free)

Image processing artifact 

Dust on imaging plate

Image processing artifact (Hardware induced) 

Dust on imaging plate

Image processing artifact 

Dust on imaging plate

Image processing artifact 

Dust on imaging plate

Image processing artifact 

Dust over roller ◦ Cause  Dust on roller

◦ Appearance  Localized radiopacities

◦ Solution  PM by vendor, call service

Image processing artifact 

Disparity artifact ◦ Cause  Malfunction of roller in CR reader

◦ Appearance  Defective scanning resulting in alteration in image contrast

◦ Solution  Call service

Image processing artifact 

Disparity artifact

Image contrast alteration in lower half of the CXR, due to exposure to CR reader laser beam for longer time, resulted in brighter image output.

Image processing artifact 

Damage of IP due to roller ◦ Cause  Mechanical damage of IP during transport through roller

◦ Appearance  Focal linear radopacities

◦ Solution  Call service

Image processing artifact 

Damage of IP due to roller Linear radiopacities (arrows) along right lateral chest wall which can easily misdiagnose as calcified granulomas in lung

Image processing artifact 

Malfunctioning roller ◦ Cause  Slipping of feed roller from transport

◦ Appearance  Half-read image

◦ Solution  Call service  PM by vendor

Image processing artifact 

Malfunctioning roller

Image processing artifact 

Plate reader artifact ◦ Cause  Dirt over light guide

◦ Appearance  Linear radiopaque line

Image processing artifact 

Plate reader artifact ◦ Solution  Open the CR reader and pull and push the provided metal wire several times

Image processing artifact 

Plate reader artifact

Image processing artifact 

Cassette related artifact ◦ Cause  Cracked lead coating on back of cassette

◦ Appearance  Linear radiolucent line

◦ Solution  Cassette replacement

Image processing artifact 

Cassette related artifact

Image processing artifact 

Communication error artifact ◦ Cause  Power failure during image transmission

◦ Appearance  Missing line or pixels in resulting image

◦ Solution  DO NOT process the IP during electric supply check  Connect the power to essential socket but not nonessential one

Image processing artifact 

Communication error artifact

Image processing artifact 

Communication error artifact

Image processing artifact 

Data cable malfunctioning artifact ◦ Cause  Failure of data cables in the power unit of CR reader

◦ Appearance  Alternating radiopaque and radiolucent line

◦ Solution  Call service, replace data cables

Image processing artifact 

Data cable malfunctioning artifact

Image processing artifact 

Erasure related artifact ◦ Cause  Malfunction of the erasure light

◦ Appearance  Residual image left in IP

◦ Solution  Call service, replace the erasure light

Image processing artifact 

Erasure related artifact

DDR Artifact

DDR artifact 

Noisy detector power supply ◦ Cause  Problem of power supply to the detector

◦ Appearance  Unusual vertical line appearance

◦ Solution  Call service, replace the power supply

DDR artifact 

Noisy detector power supply

DDR artifact 

Fibre optic cable malfunction ◦ Cause  Fibre optic cable malfunction

◦ Appearance  Dots or vertical lines

◦ Solution  Call service, replace the optic cable

DDR artifact 

Fibre optic cable malfunction

DDR artifact 

Latent image ◦ Cause  Over-exposure  frequently exposure

◦ Appearance  Latent image

◦ Solution  Wait for the disaapear of latent image

DDR artifact 

Latent image

DDR artifact 

Bar code artifact ◦ Cause  Failure of the detector

◦ Appearance  Bar-code image

◦ Solution  Perform built-in bad pixel calibration  If calibration fail replace detector

DDR artifact 

Bar code artifact

DDR artifact 

Radiofrequency (RF) interference artifact ◦ Cause  Detector shield against RF interference cracked  Too close an RF source (portable case)

◦ Appearance  Many different forms, but typically generate a repeatable pattern in the radiograph

◦ Solution  Call service  Try to avoid the RF source (portable case)

DDR artifact 

Radiofrequency (RF) interference artifact

DDR artifact 

Bar artifact ◦ Cause  Failure of detector

◦ Appearance  A ‘bar’ showing in the image

◦ Solution  Call service

DDR artifact 

Bar artifact

References: 

Cesar, LJ, Schuelet, BA, Zink, FE, Saly, TR, Taubel, JP & Jorgenson, LL (2001), 'Artefacts found in computed radiography', The British Journal of Radiology, vol. 74, pp. 195-202.

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Willis, C, Thompson, SK & Shepard, J (2004), 'Artifacts and misadventures in digital radiography', Applied Radiology, vol. 33, no. 1, pp. 11-20.

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Hammerstrom, K, Aldrich, J, Alves, L & Ho, A (2006), 'Recognition and prevention of computed radiography image artifacts', Journal of Digital Imaging, vol. 19, no. 3, pp. 226-239.

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Korner, M, Weber, CH, Wirth, S, Pfeifer, K, Reiser, MF & Treitl, M (2007), 'Advances in digital radiography: physical principles and system overview', RadioGraphics, vol. 27, pp. 675-686.

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Drost, WT, Reese, DJ & Hornof, WJ (2008), 'Digital radiography artifacts', Veterinary Radiology & Ultrasound, vol. 49, no. 1, pp. S48-S56.

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Shetty, CM, Barthur, A, Kambadakone, A, Narayanan, N & Kv, R (2011), 'Computer radiography image artifacts revisited', American Journal of Roentgenology, vol. 196, pp. 37-47.

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Walz-Flannigan, A, Magnuson, D, Erickson, D & Schueler, B (2012), 'Artifacts in Digital Radiography', American Journal of Roentgenology, vol. 198, no. 156-161.

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