VOA标准英语2010年-CT Scan Radiation Draws Concern（在线收听）

Doctors use X-rays to view internal organs, obtain clear images of possible disease and to treat cancer. For years radiation has been used to save lives, but there is growing concern that some patients are getting more than they ask for when they undergo what's called a CT (Computed Tomography) scan.  Research has shown that exposure to radiation can cause cancer and some recent studies raise doubts about the overall safety of CT Scans.

Patricia Quirk of Illinois had radiation to treat her endometrial cancer.  The radiation killed the cancer.   It also killed her by rupturing her bowel.  The hospital record shows she was given 50 percent more radiation than she needed.

Her husband, Tom Quirk, says it should never have happened.

"I pray to God that it never happens to anybody again," said Tom Quirk.

More than half of the cancer patients in the U.S. receive radiation as part of their treatment.

The CT (Computed Tomography) Scan is a method often used to diagnose cancer. It exposes a patient to much larger doses of radiation than the usual x-ray. 

Use of the CT Scan has increased dramatically since it was introduced 40 years ago.   A 2007 report in The New England Journal of Medicine estimated that at least 62 million CT scans were conducted yearly in the United States. 
Of those, about four million were done on children. Children are 10 times more sensitive to radiation.

Recent studies reflect growing concern in the medical community about the risks associated with large amounts of radiation given to patients.  

Dr. Rebecca Smith-Bindman of the University of California San Francisco led a study of more than one thousand patients in four of the city's biggest hospitals.  She found that some patients received 20 times more radiation than others during CT scans for the same condition.

"We don't have standards that say this is allowable.  This is not allowable.  This is an area that really lacks close oversight," she said.

In two other cities, Los Angeles, California and Huntsville, Alabama, a study also showed significant differences in radiation. In some cases, patients received eight times more radiation for the same scan.  

In any CT scan, the radiologist determines the required level of radiation.  A medical physicist calibrates the scanner. But nowhere on the screen is an indication of how much radiation the patient is really getting.

The American College of Radiology says its members are concerned about the amount of radiation patients receive. A spokesman for the group says CT scans are frequently used in hospital emergency rooms because the results can be read quicker than with other tests, like ultrasound or MRIs, that do not use radiation.

Radiologists say patients should ask their doctors whether tests using radiation are needed, and, if so, ask for the lowest dose possible. 

The doctor should also check to make sure the amount of radiation given is the correct amount.