A Look Into Computed Radiography (CR)

Computed Radiography (CR) is a generic term referring to the class of digital radiographic detectors that use photostimulable storage phosphors (PSP) to absorb incident x-ray energy with the subsequent storage of proportional charge at located energy traps and subsequent laser-moderated photo-stimulated luminescence (PSL) to measure and convert the trapped energy into corresponding digital image. Advances in CR detector and readout technology have been the introduction of dual-side readout methods, structured PSP detectors, and parallel readout methods.

The first CR systems were developed in the mid-1980s and were initially a curiosity with little clinical relevance because of the large size, long processing time, and extremely high cost. Anecdotal research and reports with these systems demonstrated that they could compete with screen-film radiography, but there was really no overriding need for such expensive systems that still had to print film. There were no widespread capabilities to view images electronically and therefore little or no advantage to contemporary screen-film technology of the day. Deployment at large medical centers and military facilities was spurred chiefly by research opportunities and the early military push to support future electronic imaging development.

The clinical use of digital radiography (DR) began in earnest in the early to mid-1990s, with the development of first-generation PACS (Picturing Archiving and Communication System) and the introduction of smaller footprint, lowest cost CR systems. There was a wide array of CR systems, from large, multiple-input readers to single-plate desktop units and integrated, cassetteless readout systems that function similarly to flat panel detectors (FPD) with regard to acquisition, display speed, and image quality.

The technology of CR systems represents a refinement of earlier systems, whereby a PSP imaging plate, manufactured with a barium fluorobromide (BaFBr) compound, is layered on an opaque substrate covered with a transparent protective layer and contained in a cassette with an identical size to screen-film cassettes, thus allowing direct replacement and use in conventional radiography systems.

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