The use of X-rays for diagnosing feline ailments is an important part of veterinary practice. Most practices today have their own equipment for this purpose, but if you visit a small clinic, you will probably have to take your pet to the main surgery for an examination. Many people think of using X-rays for diagnosing bone ailments, but they are also useful for highlighting soft tissue problems, such as lung disorders or an obstruction in the intestinal tract.
Q. Why won’t my vet let me hold my cat when she is having an X-ray?
Simply because of the risk of exposure to radiation, which is not to be recommended, particularly in the case of pregnant women.
Q. How is the X-ray film processed?
Either the film will have to be removed and developed manually in a darkroom which takes about fifteen minutes, or it can be automatically developed, which is easier and quicker and is now commonly used.
Q. How is the film interpreted?
The problem may be obvious when the film is placed on a light box for viewing. With a fracture, the break will normally show as a darker area than the surrounding bone, which the X-ray does not penetrate to the same extent.
Making a Radiograph, the X-ray picture of a cat, is similar to the process used for people, but in many cases, of course, the cat will have to be adequately restrained, so that it keeps still. Any movement will otherwise blur the resulting image. So your vet may well recommend either sedating your cat or giving him a general anaesthetic.
It’s equally important to position the cat correctly in the first place, with two images invariably being required, from different angles, in order to give a clear impression of the area of the body being studied. The film is placed in a cassette, with the sides being marked with clips as I and R, to orientate viewing of the X-ray once it is developed. The film needs to be positioned directly beneath the machine’s beam, to avoid distortion, so the cassette itself is usually placed flat on the table, with the cat resting on top.
Highlighting the area under investigation can be helpful, to give a better outline. This is done using contrast media, which can be divided into two groups. `Negative’ contrast media, such as air, create a dark impression on the film and can be useful when examining the bladder or colon, while ‘positive’ contrast media, like barium sulphate, appear as white areas on the film. Barium is helpful for showing obstructions in the gastrointestinal tract. Most X-rays need to be interpreted by the experienced eye.
The circulatory system can also be examined by means of radiography, with an iodine-based dye being injected for this purpose.
The protective clothing worn by radiographers is very heavy because it incorporates lead, which X-rays can’t penetrate.
Sensitive film badges also have to be worn, which will reveal just how much radiation the person has been exposed to —the safety limits are laid down in official guidelines.