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Get the most out of your digital radiography equipment (Proceedings)

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Apr 01, 2010

Digital radiography is the fastest growing imaging modality in medicine. It is replacing conventional analog imaging in practices across the United States. Eventually all veterinary practices will utilize this modality. Although cost of digital radiography is an issue, vendors continue to offer better equipment and competition in the free market will likely lower start-up costs for practitioners.

Basic concepts of digital radiographic technology

Digital radiography is filmless and uses conventional x-ray equipment (x-ray machine, table, grid, Bucky tray, etc.) to generate an image. There is no dark room, film storage, or processing with chemicals and light boxes are not used to interpret the image. The final image is presented on a computer screen in a digital format. Digital radiography comes in two forms: CR or computed radiography and DDR or direct digital radiography.

• Computed radiography uses a flexible image plate containing phosphors for image capture. When phosphors in the image plate are struck by x-rays incident energy is transferred to electrons of the phosphor to produce a latent image similar to conventional x-ray film. After x-ray exposure the image plate is fed into a "reader" where a laser converts captured energy to light. Light energy is amplified and converted to an electronic signal, which is digitized. Computer software automatically manipulates the digital data and the interpreter is presented with a final image read from a computer monitor.
• With DR the image is acquired on a rigid image plate, which also performs electronic capture and digitization. Unlike CR a reader is not used and digital data is sent directly to the computer via a cable connection. Depending on the system, the direct image plate converts x-ray energy to light and subsequently an electrical signal, or may directly convert x-ray energy to an electrical signal. In either case, time is saved compared to CR because a physical processing step is unnecessary-a distinct advantage in busy small animal practices and in equine imaging.
• Picture Archiving and Communications System (PACS). The PACS is a network that includes the imaging computer, software, image storage and viewing monitors. It facilitates all facets of the imaging process: image review, transmission of images, reporting and, local and remote storage...
• The DICOM file format is used to acquire, review and store digital images. DICOM (Digital Image & Communications in Medicine) file format is the industry and the FDA standard. Once acquired, these files cannot be altered due to several protective layers. However they can be manipulated and saved as another format (.tif, .jpg). DICOM files contain original image data and are used in legal cases. These files are preferred for manipulation by software programs because they are universal and contain all of the image data.
• Advantages of digital imaging
     o Improved contrast
     o Wide range of gray scale
     o Ability to adjust scale of contrast after image is made
     o Potentially faster imaging—throughput
     o Potentially fewer "re-takes"
     o No films and no film storage
     o No processor and no chemicals
     o No lost films
     o Computer friendly
• Disadvantages of digital imaging:
     o Less resolution (detail) compared to conventional radiography
     o High exposure factors
     o More personnel exposure
     o Shorter tube life—x-ray machine
     o Must have multiple digital viewing screens for interpretation
     o Proper interpretation requires a dedicated software program
     o (Microsoft Photo Editor is not enough!)
     o Must have an archiving system
     o Storage on CD ROM disks, is not an acceptable option
     o Expensive