Computerized axial tomography (CAT) scans take the idea of conventional X-ray imaging to a new level. An X-ray image is basically a shadow. When you shine a "light" on one side of the body a piece of film on the other side registers the silhouette of the bones.

Instead of finding the outline of bones and organs, the CAT scan X-ray beam moves all around the patient scanning from hundreds of different angles. The computer takes all this information and puts together a 3-D image of the body. Doctors can even examine the body one narrow slice at a time to pinpoint specific areas.

Scanning Procedure

The CAT machine looks like a giant donut tipped on its side. The patient lies down on a platform that slowly moves through the hole in the machine. The machine records X-ray slices across the body in a spiral motion. The computer varies the intensity of the X-rays in order to scan each type of tissue with the optimum power.

After the patient passes through the machine the computer combines all of the information from each scan to form a detailed image of the body. Of course, it is not usually necessary to scan the entire body. More often, doctors will scan only a small section. Since they examine the body slice by slice, CAT scans are more comprehensive than conventional x-rays.