Patients urged to weigh CT scan risks and benefits

* New studies prompt concern about cancer risk from CT scans

* Experts say an individual’s cancer risk is low from CT scan

* Use of CT scans has soared in past three decades

CHICAGO, Dec 15 (Reuters) - Patients should not let recent studies showing that exposure to radiation from a CT scan may raise their cancer risk scare them away from getting this type of X-ray when it is needed, radiology specialists said on Tuesday.

A CT scan, also known as computed tomography, gives doctors a view inside the body, often eliminating the need for exploratory surgery. But CT scans involve a much higher radiation dose than conventional X-rays. A chest CT scan exposes the patient to more than 100 times the radiation dose of a typical chest X-ray.

Radiology specialists emphasized that an individual’s risk of developing cancer as a result of radiation exposure from a single CT scan is very low, especially when compared to the risk to them from a disease that a CT scan may help identify.

Use of these tests for detecting tumors and heart disease and diagnosing other conditions such as appendicitis has risen dramatically in the past three decades.

Dr. Elliot Fishman, a professor of radiology at Johns Hopkins University in Baltimore, said some studies equated the risk of getting cancer from a single CT scan to the risks of dying in a long car ride.

“If you are going to a good physician who orders a study (a CT scan) that he or she thinks you need, you need to get the study,” Fishman said in a telephone interview.

Recently published research has raised concerns about the risks of radiation exposure from diagnostic tests, especially CT scans. Two studies appearing on Monday in the Archives of Internal Medicine estimated that CT scans cause thousands of U.S. cancer cases and cancer deaths each year.

The estimates of cancer cases caused by CT scans were based on the rates of cancer that occurred in people exposed to radiation from the atomic bombs dropped on the Japanese cities of Hiroshima and Nagasaki at the end of World War Two. But many experts disagree on whether that model offers a fair comparison.


“No published studies show that radiation from imaging exams causes cancer,” the American College of Radiology, a group made up of 34,000 doctors specializing in radiology, said in a statement.

“Most CT is performed in controlled settings and results in limited radiation exposure to a small portion of the body. Atomic bomb survivors experienced instantaneous exposure to the whole body,” the group said.

The group added that assumptions based on this model “should be considered, but not accepted as medical fact.”

CT scan equipment is changing. Makers such as GE Healthcare GE.N, Siemens SIEGn.DE, Philips PHG.AS and Toshiba Medical Systems 6502.T have developed CT scanners in the past few years that deliver far lower doses, Fishman said. "The CT of two or three years ago is not the CT of today," he said.

CT scan use in the United States has grown sharply. About 70 million CT scans were done on Americans in 2007, up from 3 million in 1980.

“I think a lot of things are driving it,” Dr. Rita Redberg, editor of the Archives of Internal Medicine, said in a telephone interview. “The pictures are beautiful. I think in general we have a belief that more tests and more information is better.”

Dr. Rosaleen Parsons, a radiologist at Fox Chase Cancer Center in Philadelphia, said instead of scaring patients, the studies should inspire them to ask questions about the tests they are getting, and to ensure that those they get are from centers that are fully accredited by the American College of Radiology.

Patients can search for an accredited facilityhere

Editing by Maggie Fox and Will Dunham