A CAT scanner，however，uses a group of X­rays to give a cross­sectional (截面的 ) view of a specific part of the body.A fine group of X­rays is scanned across the body and around the patient from many different directions.A computer studies the information from each direction and produces a clear cross­sectional picture on a screen.This picture 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 organs.The latest CAT scanners can even give clear pictures of active，moving organs，just as a fast­action camera can “stop the action”，giving clear pictures of what appears unclear to the eye.And because of the 360­degree pictures，CAT scans show clear and complete views of organs in a manner that was once only shown during operation or examination of a dead patient.

　　Frequent appearance before X­rays can cause skin burns，cancer or other damages to the body. Yet CAT scans actually don't cause the patient to more radiation than regular X­rays do.CAT scans can also be done without getting something harmful into the patient，so they are less risky than regular X­rays.

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

　　[解题导语]　本文是一篇科技说明文，介绍了(CAT scans)电子计算机X线断层扫描在医学上的应用和优点。

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