CCD cameras

CCD camera radiographic systems generate an X-ray image when X-rays interact with a fluorescent (light-producing) screen that is attached to the underside of the X-ray table. The light produced from this interaction is then focused by a lens and captured by the CCD chip. In essence, the CCD camera photographs the light produced from X-rays interacting with a screen.

CCD chips are relatively small (2.5 x 2.5 cm to 8 x 8 cm). The large demagnification factor needed to reduce the size of the patient's image to the size of the CCD may result in loss of information, which has limited the quality of CCD-based images in the past.^2,10 Advances in CCD technology, however, have overcome this limitation, and CCD-based machines are now accepted in human radiographic applications.^12-15 The veterinary experience with CCD cameras is more limited than with CR and flat panel DR detectors. CCD radiography is used extensively in human and veterinary dental radiography because of the small field of view.

Both CR and DR systems create a set of raw data that will be used to produce a diagnostic radiographic image. Each vendor has a different method of image processing that may involve several steps that vary in complexity and involve mathematical manipulations of the raw data. Although there are marked technical differences among various vendors' radiographic systems, differences in image quality stem mainly from a system's ability to effectively process the image and not necessarily from the type of equipment used to obtain the image. CR is a relatively inexpensive system of digital radiography that shares a similar workflow with film-based radiography. DR technologies enable veterinarians to generate radiographic images within seconds of acquisition.

Sarah M. Puchalski, DVM, DACVR
Department of Surgical and Radiological Sciences
School of Veterinary Medicine
University of California
Davis, CA 95616

REFERENCES

1. Bruce R. CR versus DR—what are the options? AuntMinnie, 2003. Available at: http://www.auntminnie.com/index.asp?sec=ser&sub=def&pag=dis&ItemID=58851.

2. Bushberg JT, Seibert JA, Leidholdt Jr, EM, et al. Digital radiography. In: The essential physics of medical imaging. 2nd ed. Philadelphia, Pa: Lippincott, Williams & Wilkins, 2002.

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8. Fischbach F, Ricke J, Freund T, et al. Flat panel digital radiography compared with storage phosphor computed radiography: assessment of dose versus image quality in phantom studies. Invest Radiol 2002;37:609-614.

9. Goo JM, Im JG, Kim JH, et al. Digital chest radiography with a selenium-based flat-panel detector versus a storage phosphor system: comparison of soft-copy images. AJR Am J Roentgenol 2000;175:1013-1018.

10. Hornof W. Digital radiography: The available technologies and how to separate hype from reality, in Proceedings. Am Vet Med Assoc Annu Convention 2005.

11. Peer S, Neitzel U, Giacomuzzi SM, et al. Direct digital radiography versus storage phosphor radiography in the detection of wrist fractures. Clin Radiol 2002;57:258-262.

12. Kroft LJ, Geleijns J, Mertens BJ, et al. Digital slot-scan charge-coupled device radiography versus AMBER and Bucky screen-film radiography for detection of simulated nodules and interstitial disease in a chest phantom. Radiology 2004;231:156-163.

13. Kroft LJ, Veldkamp WJ, Mertens BJ, et al. Comparison of eight different digital chest radiography systems: variation in detection of simulated chest disease. AJR Am J Roentgenol 2005;185:339-346.

14. Veldkamp WJ, Kroft LJ, Boot MV, et al. Contrast-detail evaluation and dose assessment of eight digital chest radiography systems in clinical practice. Eur Radiol 2006;16:333-341.

15. Veldkamp WJ, Kroft LJ, Mertens BJ, et al. Digital slot-scan charge-coupled device radiography versus AMBER and Bucky screen-film radiography: comparison of image quality in a phantom study. Radiology 2005;235:857-866.