Howcan you find out what is going on inside a person' S body一without opening the patient up?Regular X rays can show a lot. CAT scans canshow even more. They can give athree-dimensional view of body organs.Whatis a CAT scan? CAT stands for Computerized Axial Topography(层面X线照技术). It is a special X-ray machine that obtains a 360-degreepictureof a patient' S body.Doctorsuse X rays to study and diagnose diseases and injuries within the body. X rayscan locate foreign objects inside the body or takepictures of some internalorgans if special substances as dyes or special liquids are added to the organsto be X-rayed.ACAT scanner, however, uses a beam of X rays to give a cross- sectional(横断面的) view of a specific part of thebody. A fine beam of X rays isscanned across the body and rotated around thepatient from many different angles. A computer analyzes the information fromeach angle andproduces a clear cross-sectional image on a screen. This imageis then photographed for later use. Several cross-sections, taken one afteranother,can give clear "photos" of the entire body of any body organs. Thenewest CAT scanners can even give clear images of active, moving organs,justas a fast-action camera can "stop the action" , giving clear images of whatappears only mistily to the eye. And because of the 360-degreepictures, CATscans show 3-dimensional views of organs in a manner that was once onlyrevealed during surgery of autopsy (examining a deadpatient).Toomuch exposure to X rays can skin burns, scanner or other damage to the body.Yet CAT scans actually don' t expose the patient to moreradiation thanconventional X rays do. CAT scans can also be done without injecting dyes intothe patient, so they are less risky than regular X-rayprocedures.CATscans provide accurate, detailed information. They can detect such a thing asbleeding inside the brain. They are helping to save lives.

49. What is NOT TURE of a CAT scan?

A. It utilizes computertechniques.

B. It gives clear images ofactive, moving body parts.

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

D. It is safer than regular X-rayprocedures.

50. A "foreign object" (Para.3, line 2)most probably refers to().

A. new thing that is unknown tothe doctor.

B.a severely injured part insidethe body.

C.a substance that gets insidethe body by chance.

D. a strange organ that has grownin the body.

51. What is the special feature of thelatest CAT scanners?

A. helps to find out what is going on inside aperson' S body without opening it up.

B. It provides clear photos of moving organs.

C. It won' t cause serious skin burns, cancer orother damage to the body.

D. It can take 3-dimensional pictures ofinternal organs.

52. It is implied but not directly statedin the passage that().

A. CAT scanners can take photos of either thewhole body or one part of it.

B. CAT scanners do not need the injection of dyes.

C. CAT scanners are more expensive than regularX-ray procedures.

D. the patient can be exposed to a slight amountof radiation safely.