Digital Veterinary Radiography Systems
Radiography comprises the majority of diagnostic medical images generated in veterinary practice
but other imaging modalities such as ultrasonography, CT, MRI, and nuclear imaging are also very important
and commonly available in specialty practices and academic centers. Imaging provides a large amount of information by noninvasive means.
It does not alter the disease process or cause unacceptable discomfort to the animal.
Although radiography itself is painless, sedation is often desirable to reduce anxiety and stress associated with the procedure,
to promote acquisition of good diagnostic studies with minimal repeats, and to control pain associated with manipulation in animals
with painful disorders such as fractures and arthritis.
Darkroom (Not Use Anymore)
As digital image capture replaces radiographic film, darkrooms will no longer be required .
However, because radiographic film is still used by many veterinary practices, a brief description of darkroom procedures is provided .
Once the film is exposed, it must be processed in a darkroom to make the latent image recorded on the film visible and-
fixed so that the image remains unchanged once the film is brought into the light .
Care should be taken to be sure no exterior light enters the darkroom .
Even very small amounts of white light will markedly fog a film and decrease its diagnostic quality .
Safelights used to illuminate darkrooms include filters that remove the frequencies of the light to which the film is sensitive, so the film will not be exposed .
Films vary in their spectral sensitivity; therefore, when replacing a safelight filter, the spectral requirements of the filter must be specified .
Automatic processing systems improve processing quality and consistency and reduce the processing time compared with traditional hand film developing .
Relatively few films processed per week can justify the purchase of an automated processing system .
In any case, film processing must be done in strict accordance with the specified time and temperature requirements of the film being used .
These requirements have been standardized for many years, and automated systems are designed to meet them .
Whether processing is manual or automated, the chemicals must be handled with care .
Contamination of the darkroom with chemicals can ruin film, screens, and clothes .
Fumes from the chemicals may be harmful, and some people may be more sensitive than others, especially to the fixer solution .
Cross contamination of the developer solution with fixer inactivates it and requires replacement of the developer .
Improper handling of chemicals results in many artifacts on films as well as potential health hazards to the operators .
Filmless Radiography
Image recording systems do not require the use of film, screens, or processing chemicals .
They have several advantages over conventional film radiography :
• radiographs cannot be lost if adequate data safeguards are used
• there is no need for film storage and its attendant space and environmental requirements
• the process allows for manipulation and enhancement after the image has been recorded
• images can be transmitted electronically to a remote location for immediate interpretation
• the images are generally available more quickly, usually within 30 sec
• there is no need for a darkroom
These systems can be divided into two categories: computed radiography (CR)
in which a semiconductor plate contained in a cassette is exposed in the usual fashion and
then read electronically inside a special reader that detects the magnitude of electrostatic charge on each of the semiconductor
elements within the plate; and direct digital radiography (DR),
in which a cesium iodide scintillator array absorbs the x-rays,
producing a light pulse detected by a large array (millions) of amorphous silicone photodiode/transistor elements .
In both systems, the electrical output from each of the detector elements is proportional to the number of x-rays
that strike the detector element and is mathematically quantifiable, hence the term “digital images .
In both systems, the data produced are processed by a computer, which generates the image on a monitor
according to a previously determined processing algorithm that is specific to the region being radiographed .
Processing algorithms are critical to the development of diagnostic images .