Computerized axial tomography, or CAT, scan machines are a more sophisticated version of X-ray machines.
Instead of imaging the outlines of bones, CAT scans form a 3-D model of a patient's insides using X-rays. A regular X-ray image is basically a silhouette of the bones, and is useful for many things, but it does not provide a complete picture of an object's shape.
With a CAT scan, doctors can examine the body one narrow "slice" at a time, to focus on specific areas.
A CAT scan machine uses an X-ray beam that moves around the patient, scanning from many different angles. It then combines this information into a 3-D image of the body.
How does this process work? The patient lies down on a platform, which moves through a large donut-like hole in the machine. There is a tube mounted on a moveable ring around the edges of the hole, with a tube that produces X-rays, and several X-ray detectors.
The ring turns so that the tube and detectors revolve around the body. Each turn of the ring scans a narrow "slice" of the body, and each time the platform moves the patient's body a little farther into the hold so the detectors can scan the next section. A computer connected to the system can vary the intensity of the X-rays, since different types of body tissue require different kinds of X-rays.