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About.com Health's Disease and Condition content is reviewed by Sanja Jelic, MD

Computed tomography (CT) scan / computerized axial tomography (CAT) scan, is a procedure in which cross-sectional images (x-rays taken from many different angles) of structures of the body are created and processed through a computer forming a three dimensional image called a tomogram. It is the three dimensional imaging that makes CAT scans more effective than chest x-rays.

What are CAT Scans Used for?

CAT scans are used to detect abnormalities in structures of the body. Computed tomography is a noninvasive procedure, meaning no entry of the body is necessary. CAT scans are generally an outpatient procedure.

Are CAT Scans Dangerous?

CAT scans emit very low levels of radiation, and is therefore considered a safe procedure. However, if you are pregnant, you should notify the technician before the procedure, no matter what trimester you are in.

What Should I Expect When Getting a CAT Scan?

Prior to the CAT scan, you will be asked to remove all of your jewelry and any clothing with snaps, zippers, or other metallic materials. Generally, you will be asked to wear a hospital gown during the CAT scan.

How Long Does a CAT Scan Take?

You will be asked to lie on a movable table, which slides into a doughnut-shaped computed tomography scanner. You will need to stay in the scanner for 30 to 90 minutes to complete the CAT scan.

Why Must I Lie Still During the CAT Scan?

It is very important to lie perfectly still during the CAT scan. Any slight movements could cause blurred images and hinder an accurate diagnosis. You may also be asked to hold your breath at specified times during the CAT scan.

What if I Start to Feel Claustrophobic During the CAT Scan?

During the CAT scan, you will be able to communicate with the technician via a intercom system. If you feel uncomfortable at any time during the CAT Scan, tell the technician. Sometimes just talking to someone during the procedure will make you feel better.

How Do Spiral / Helical CAT Scans Differ From Regular CAT Scans?

If you are lucky enough to find a facility that has a spiral or helical scanner, you will spend less time lying on your back for a CAT scan. Spiral / helical scans are newer scanners that are faster and more accurate.

Related:
The Debate Over Full-Body CAT Scans
How Do Chest X-Rays Differ from CAT Scans?
Which is Better: CAT Scan or Chest X-Ray?

Source: Healthcommunities.com