The effectiveness of X-rays as a veterinary diagnostic tool outweighs the potential risks of exposure to radiation. In dogs, X-rays are commonly used to identify broken bones, determine the number of foetuses and stage of a pregnancy, evaluate stomach and bowel obstructions and diagnose major medical issues like tumours and other disease.
An X-ray is a picture of the inside of a dog's body. The process of X-ray uses low levels of electromagnetic radiation to create images of internal organs, bones and teeth. X-rays were one of the first forms of medical imaging used in veterinary medicine, providing painless diagnosis of medical conditions and canine emergencies. Different kinds of X-rays are used for specific cases, for example, bone X-rays or chest X-rays.
To create an X-ray image, a plastic cassette containing film is positioned under the target area. The film is protected from scratches and image distortion by the plastic cassette. Cassettes come in different sizes, appropriate to the area being X-rayed. X-ray equipment is mounted on a movable arm positioned over the target area. The X-ray is turned on, creating grey-shaded images on the film. The shades on the film are determined by the density of the tissue and bone in the target area. The densest areas are white, less dense areas are light grey. If multiple views are required, staff will reposition the dog and take additional films. Shooting X-ray film generally takes between five and 10 minutes. The exposed film is processed to get the images, which takes an additional 10 to 30 minutes.
Judicious use of X-rays is not hazardous for a dog, and the diagnostic benefits outweigh any risks from momentary exposure to radiation. If a dog is excitable, in pain or uncomfortable, it may be necessary to sedate or anaesthetise him to get clear X-ray images. The risks of sedation and anaesthesia should be considered by the veterinarian. Sometimes, it is the only way for staff to properly position the dog for X-rays, and helps avoid overexposure to radiation from multiple failed X-ray attempts.
X-rays are often used to determine the number of foetuses and their position in an expectant female. This can help prevent pregnancy trauma and birthing emergencies and is not harmful to the mother or to the puppies.
Diagnostic X-rays do carry an element of risk, as they do in humans. Repeated exposure should generally be avoided; shield the areas of the dog not being X-rayed from radiation if possible, just as humans and medical personnel take precautions not to be overexposed.
Ultrasound is used as an alternative to diagnostic X-rays in dogs. Ultrasound provides images of internal organs, tissue and bones with the direction of high-frequency sound waves and the resulting echo waves. Ultrasound may be more costly than X-rays. The results of ultrasound imaging are accurate and generally a good substitute for X-rays. At times, however, a veterinarian may indicate preference for X-rays over ultrasound. When examining a pregnant dog to determine the number of foetuses, for example, X-rays will often provide a clearer image of backbones in the womb.