DR, or direct X-ray (DX), generally refers to one of three system types. The unifying characteristics of these systems are
that an image is produced nearly instantaneously and that the same X-ray detector is used for every exposure.1,2,6-8 Two DR systems fall into the flat panel category. Flat panel detectors are a commonly used DR system in veterinary medicine.
The other type of DR system is a charge-coupled device (CCD) camera.
3. A schematic of a scintillation style, flat panel DR detector. X-ray photons pass through the detector and interact with
a scintillation crystal that emits light. Each pixel of the detector houses electrical hardware, which maps the light as it
Flat panel detectors
The DR flat panel detectors are further subdivided into panels that scintillate (i.e. emit light energy that is digitized and recorded when X-ray photons interact with the detector elements) (Figure 3) and panels that create an electrical current when X-ray photons interact with the detector; the current is then converted
to a radiographic image.9 In either case, this process is nearly instantaneous, and images can generally be viewed within seconds of their acquisition.
Scintillation detectors are currently the most prevalent veterinary DR system.10 Theoretically, in systems that do not scintillate, the lack of the intermediate light-producing step should provide these
systems with superior resolution. The clinical significance of this difference has yet to be determined.1,7-9,11
The various vendors' panels have different physical dimensions, but all have a slightly smaller active detection area than
the overall dimensions of the panel. The size of the radiograph is limited to the detector size, and care should be taken
to choose the correct imaging surface size for the types of patients and studies being produced. Generally, the dimensions
of this type of detector will be different from conventional film-screen cassettes, occasionally requiring alterations in
radiographic examination tables or preexisting cassette holders (equine practice). Furthermore, to electronically synchronize
the DR system with the existing generator, a minor system modification, which is usually done by the vendor, is necessary.
As with CR systems, both flat panel and CCD DR systems require purchasing a means of image storage and review.