How can you find what is going on inside a person's body—without opening the patient up？ R

egular X-rays can show a lot. CAT scans can show even more. They can give a three- dimensional view of body organs.

What is a CAT scan？ CAT stands for Computerized Axial Tomography. It is a special X-ray machine that obtains a 360-degree picture of a small area of a patient's body.

Doctors use X-rays to study and diagnose diseases and injuries within the body. X-rays can locate foreign objects inside the body or take pictures of some internal organs—if special substances such as dyes of special liquids are added to the organs to be X-rayed.

A CAT scanner, however, uses a beam of X-rays to give a cross-sectional view of a specific part of the body. A free beam of X-rays is scanned across the body and rotated around the patient from many different angles. A computer analyzes the information from each angle and produces a clear cross-sectional image on a screen. This image is then photographed for later use. Several cross-sections, taken one after another, can give clear "photos" of the entire body or of any body organ. The newest CAT scanners can even give clear images of active, moving organs, just as a fast-action camera can "stop the action", giving clear images of what appears only mistily to the eye. And because of the 360-degree pictures, CAT scans show 3-dimensional views of organs in a manner that was once only revealed during surgery or autopsy (examining a dead patient).

Too much exposure to X-rays can cause skin bums, cancer or other damage to the body. Yet CAT scans actually don't expose the patient to more radiation than conventional X-rays do. CAT scans can also be done without injecting dyes into the patient, so they are less risky than regular X-ray procedures.

CAT scans provide accurate, detailed information. They can detect such a thing as bleeding inside the brain. They are helping to save lives.

What is NOT true of a CAT scan？

A．It utilizes computer techniques.

B．It gives clear images of active, moving body parts.

C．It can stop the action of an organ for a fraction of a second.

D．It is safer than regular X-ray procedures.