CT

Alternative names:

CAT scan; computerized tomography

How the test is performed:

You are asked to lie on a narrow table (gantry) that slides into the center of the scanner. The scanner looks like a tube surrounded by the imaging equipment. A contrast-media (dye) may be injected into a vein to help define certain tissues. The table will advance slightly (1/4 to 1/2 inch) between each scan to align for the next cross-section image. The technologist operating the computer may indicate when it is necessary to control breathing. A sound system is built into the machine to allow communication with you during the test.

During the test, it is very important to remain still. If a patient is restless or traumatized, you may be given a sedative. Each exposure takes a few seconds. The complete scan takes about 1 hour.

How to prepare for the test:

The health care provider may advise fasting for 4 to 6 hours if contrast dye is to be used or if sedation is anticipated (consult the health care provider). You wear a hospital gown during the procedure and asked to sign a consent form.

How the test will feel:

The X-rays are painless. The primary discomfort may be from the need to lie still on the table.

If a dye is needed to increase the contrast between different tissues or organs, it is administered by injection into a vein. The injection may sting and the site may be tender to the touch for several minutes. Dye injections may cause a cool or warm sensation, a metallic taste and, in a few cases, hives.