A CAT (computed axial tomography) scan, or CT scan, is a painless test that uses special x-ray equipment to obtain multiple images of internal body structures. The images are then placed together by computer technology to produce cross-sectional views of the targeted area. CAT scans use digital x-rays which provide greater detail than standard x-rays.

CAT scans are usually performed in a hospital, outpatient clinic or imaging center. They are typically performed by a radiologist and radiology technicians who specialize in these types of imaging exams. The results of a CAT scan may be interpreted by a variety of physicians (e.g. oncologist, surgeon), depending the purpose of the test.

CAT scans are taken in a special device that contains a donut-shaped tube with a movable bed in the center. The tube contains both an x-ray source and rows of x-ray detectors. The x-ray source is rotated 360 degrees around the patient, who is placed on a table within the tube. As the table moves through the tube, multiple images are taken from various angles. The screen and computer that analyzes the images are usually located in a separate area or room.

In some cases, a special dye (contrast medium) may be given to the patient (e.g., swallowed, intravenously or by enema) and a second set of pictures is taken. The dye helps highlight certain regions of the body to provide a clearer view.

The time required for a CAT scan depends upon the area under study and the type of CAT scanner being used for the procedure. Generally, a CAT scan takes 10 to 20 minutes, but may take up to an hour to complete. Some patients may be given a sedative for the procedure and they will not be able to drive themselves home from the test site. Otherwise, patients can return to their usual daily activities.

CAT scans are frequently used to diagnose a number of medical conditions, including cancer. The test can help detect malignant tumors and provide information about their size and location. In addition, CAT scans can be used to help guide biopsies inside the body, and to help plan radiation therapy or surgery.