November 27, 2024
Cat Scans
In our last column we covered ultrasound scanning as a way to image your pet. This week, we're going to look at another way of seeing inside the animal body: the CAT Scan. “CAT'' is an abbreviation of “computed tomography”. This is derived from the Greek words “tome”, meaning “slice”, and “graphi” which means “to write”. The reason this name is used is because CAT scans make images of the body in slices. These slices are then assembled to make a study of the body.
A CAT scanner is a type of x-ray machine. It is very large and looks like a doughnut. Inside the doughnut is an x-ray tube and a semi-circle of sensors. The patient lies on a tray that can move in and out of the doughnut. Images are generated when X-rays pass through the body to the sensors in a rotating arc. As the tray moves in and out of the doughnut, these images are generated in slices. These slices are then transmitted to a computer to form a complete picture of the area under examination. The images can be two-dimensional or three-dimensional depending on the computer and the requirements of the vet.
The use of CAT scans has exploded in recent decades as the price of these machines has come down. It is now reasonably routine for pets to be scanned for a range of conditions. These conditions include fractures, spinal problems, tumours and virtually any other issue you can think of in the body. When we have an animal that is undergoing a CAT scan they generally require sedation or even full anaesthesia. The reason for this is that we cannot have an animal standing up and walking off a scanner in the middle of a scan! This means that when your pet undergoes a CAT scan they usually have to be admitted to hospital for at least a day.
CAT scans have some advantages over traditional X-ray images. CAT scans have better resolution than traditional radiographs and because a number of images are taken CAT scans avoid the superimposition of structures that can happen on a plain one-dimensional X-ray. This means that interpretation of these images can often give more information than would otherwise be achievable with a normal x-ray.
CAT scans also have some disadvantages. One disadvantage is the cost of the machine. Purchase and operation of CAT scanners is expensive. Another disadvantage is the radiation dose that the patients can receive during the scan. Clinicians are aware of the need to reduce radiation exposure in patients. Therefore only patients which require a scan will undergo one. The clinician must undertake a cost-benefit analysis before ordering a scan for any particular patient to balance the risk of the scan against the benefits of increasing the knowledge of a patient’s condition.
CAT scans have undoubtedly moved veterinary medicine forward over the past two decades. They have enabled us to see deeper into the body of an animal than we have ever been able to see before. They provide more information on cases that enable us to tailor treatments better to the individual animal and improve patient outcomes. We hope that in the future costs will come down even further to broaden their use in general practice.
