Digital radiography

Source: Wikipedia, the free encyclopedia.

Digital radiography is a form of radiography that uses x-ray–sensitive plates to directly capture data during the patient examination, immediately transferring it to a computer system without the use of an intermediate cassette.[1] Advantages include time efficiency through bypassing chemical processing and the ability to digitally transfer and enhance images. Also, less radiation can be used to produce an image of similar contrast to conventional radiography.

Instead of X-ray film, digital radiography uses a digital image capture device. This gives advantages of immediate image preview and availability; elimination of costly film processing steps; a wider dynamic range, which makes it more forgiving for over- and under-exposure; as well as the ability to apply special image processing techniques that enhance overall display quality of the image.

Detectors

Flat panel detectors

Main article:
Flat panel detector
Flat panel detector used in digital radiography

Flat panel detectors (FPDs) are the most common kind of direct digital detectors.[2] They are classified in two main categories:

1. Indirect FPDs

thin film transistors (TFTs) or fiber-coupled CCDs.[3]

2. Direct FPDs. Amorphous

electron-hole pairs in a-Se, and the transit of these electrons and holes depends on the potential of the bias voltage charge. As the holes are replaced with electrons, the resultant charge pattern in the selenium layer is read out by a TFT array, active matrix array, electrometer probes or microplasma line addressing.[3][4]

Other direct digital detectors

Detectors based on

charge coupled device (CCD) have also been developed, but despite lower costs compared to FPDs of some systems, bulky designs and worse image quality have precluded widespread adoption.[5]

A high-density line-scan solid state detector is composed of a photostimulable barium fluorobromide doped with europium (BaFBr:Eu) or caesium bromide (CsBr) phosphor. The phosphor detector records the X-ray energy during exposure and is scanned by a laser diode to excite the stored energy which is released and read out by a digital image capture array of a CCD.

Phosphor plate radiography

3D image
).

After X-ray exposure the plate (sheet) is placed in a special scanner where the latent image is retrieved point by point and digitized, using laser light scanning. The digitized images are stored and displayed on the computer screen.[7] Phosphor plate radiography has been described as having an advantage of fitting within any pre-existing equipment without modification because it replaces the existing film; however, it includes extra costs for the scanner and replacement of scratched plates.

Initially phosphor plate radiography was the system of choice; early DR[clarification needed] systems were prohibitively expensive (each cassette costs £40-£50K), and as the 'technology was being taken to the patient', prone to damage.[8] Since there is no physical printout, and after the readout process a digital image is obtained, CR[clarification needed] has been known[by whom?] as an indirect digital technology, bridging the gap between x-ray film and fully digital detectors.[9][10]

Industrial usage

Security

EOD (Explosive Ordnance Disposal) training and material testing. A 105 mm shell is radiographied with battery powered portable X-ray generator and flat panel detector.

Digital radiography (DR) has existed in various forms (for example, CCD and amorphous Silicon imagers) in the security X-ray inspection field for over 20 years and is steadily replacing the use of film for inspection X-rays in the Security and nondestructive testing (NDT) fields.[11] DR has opened a window of opportunity for the security NDT industry due to several key advantages including excellent image quality, high POD (probability of detection), portability, environmental friendliness and immediate imaging.[12]

Materials

Nondestructive testing of materials is vital in fields such as aerospace and electronics where integrity of materials is vital for safety and cost reasons.[13] Advantages of digital technologies include the ability to provide results in real time.[14]

History

Direct x-ray imaging system (DXIS) - real time display

Key developments

1983 Phosphor stimulated radiography systems first brought into clinical use by Fujifilm Medical Systems.[15][16][17]
1987 Digital radiography in dentistry first introduced as "RadioVisioGraphy".[18]
1995 French company Signet introduce the first dental digital panoramic system.[19]
First amorphous silicon and amorphous selenium detectors introduced.[20][21]
2001 First commercial indirect CsI FPD for mammography and general radiography made available.[22]
2003 Wireless CMOS detectors for dental work first made available by Schick Technologies.[23]

See also

References

Library resources about
Digital radiography
  1. ^ Marchiori, Dennis M. Clinical Imaging: with Skeletal, Chest, and Abdominal Pattern Differentials. Elsevier Mosby, 2014.
  2. PMID 15933078
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  3. ^
    ISBN 978-1-4614-5066-5
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  4. ^ Ristić, Goran S (2013). "The digital flat-panel X-Ray detectors" (PDF). Third Conference on Medical Physics and Biomedical Engineering, 18-19 Oct 2013. 45 (10). Skopje (Macedonia, The Former Yugoslav Republic of): 65–71.
  5. PMID 19774158
    .
  6. ^
    PMID 21133024
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  7. ^
    S2CID 250801018
    .
  8. ^ Freiherr, Greg (6 November 2014). "The Eclectic History of Medical Imaging". Imaging Technology News.
  9. ISBN 978-0702028441
    .
  10. ISBN 9781444165036
    .
  11. ISBN 9783319207476
    .
  12. ^ "A Review of Digital Radiography in the Service of Aerospace". Vidisco. Retrieved 2021-02-02.
  13. doi:10.1016/j.nima.2008.03.016
    .
  14. ^ Ravindran, V R (2006). Digital Radiography Using Flat Panel Detector for the Non-DestructiveEvaluation of Space Vehicle Components (PDF). National Seminar on Non-Destructive Evaluation. Hyderabad: Indian Society for Non-Destructive Testing.
  15. PMID 6878707
    .
  16. PMID 16822918
    .
  17. ^ Mattoon, John S.; Smith, Carin (2004). "Breakthroughs in Radiography Computed Radiography". Compendium. 26 (1). Introduced in the 1980s by Fujifilm Medical Systems, computed radiography (CR)...
  18. ISBN 9780323291156
    .
  19. ISBN 9789048189908
    .
  20. PMID 8551983
    .
  21. PMID 7569143
    .
  22. ^ Kim, H K; Cunningham, I A; Yin, Z; Cho, G (2008). "On the development of digital radiography detectors: A review" (PDF). International Journal of Precision Engineering and Manufacturing. 9 (4): 86–100. Archived from the original (PDF) on 2017-08-09. Retrieved 2017-05-21.
  23. ISBN 978-0323079075
    .
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