A CAT scan (computed axial tomography) is a noninvasive or minimally invasive test that uses a rotating x-ray device to create computerized, detailed, cross-sectional images of body parts. It may be performed alone or with the use of a dye (contrast medium).

CAT scans, also called CT scans, are used to diagnose a number of injuries, conditions and diseases, including internal injuries, heart conditions, cancer and many causes of joint pain.

CAT scans are generally performed by a radiology technician in a hospital or outpatient clinic. During the test, the patient lies down on a scanning table, which slides slowly into a short, open-ended tunnel. If a contrast medium is used, it can be administered by injection, by mouth or through an enema. The test is painless except for brief discomfort that may be felt if an injection is used.

The length of a CAT scan varies from a few minutes to an hour, depending on the type of equipment used and the condition and body part for which it is used. Patients usually have to remain still for most of the time during a CAT scan.  Patients may usually return to normal activities after the test.