CT scanner doses vary more than people realize, a U.S. radiologist says. (Jim Cole/Associated Press)

CT scans pose a growing danger to the American public and need more regulation to improve their safety, says a report in a leading medical journal.

The report, one of two articles about medical imaging in Thursday's New England Journal of Medicine, comes a week after a story by The Associated Press detailed the overuse of imaging tests and how much the average American's radiation dose has grown in recent years.

CT scans are super-sharp X-rays that have transformed medicine by helping doctors quickly diagnose or rule out injuries and diseases. But they use far more radiation than ordinary X-rays, and too much radiation raises the risk of cancer over time.

The U.S. Food and Drug Administration and Congress are considering new measures to help prevent medical mistakes — relatively rare cases where some people are accidentally given radiation overdoses.

However, far more people face potential long-term harm from ordinary scans that are done correctly but that are overused, repeated or simply unnecessary.

Each year, 10 per cent of the U.S. population gets a CT scan, and use of this imaging is growing more than 10 per cent per year.

"That's really the area we should focus on," said the author of one of the articles, Dr. Rebecca Smith-Bindman. She is a radiologist at the University of California at San Francisco on temporary leave to do radiation research at the National Cancer Institute.

The FDA regulates scanning equipment, but lacks authority to say how doctors use it, or when tests are appropriate. No federal standards exist for how much radiation a CT scan should use, and a study Smith-Bindman led found a 13-fold variation in the dose that patients at four California hospitals received for the same type of scan.

"The doses are much higher and much more variable than people realize" for CT scanning, she said. "It's time to make it safer."

Industry efforts to curb overuse and to lower radiation doses have had little impact, she said.

"It is all voluntary," conceded Dr. John Patti, a Massachusetts General Hospital radiologist who heads the American College of Radiology's board of chancellors.

Two scientists with leadership roles in the group and extensive ties to industry and health insurers wrote in a second article in the journal that the use of high-tech imaging needs to become more selective.

Call to regulate doses

Patients who pressure doctors for tests they may not need are part of the problem, write Dr. Bruce J. Hillman of the University of Virginia, and Jeff Goldsmith, president of Health Futures Inc., a Charlottesville, Va.-based health information policy and analysis company.

Fear of being sued also leads to too many tests — a problem that won't be fixed unless there are limits on malpractice awards, they write.

And although Medicare bars doctors from having a financial stake in care they order for their patients, "a loophole" lets them do tests on machines in their offices, Hillman and Goldsmith write. Some doctors have exploited this to send patients to off-site scanning facilities they own.

Congress could give the FDA authority to set doses for CT scans the way it has allowed the agency to do so for mammograms, Smith-Bindman said.

Groups that track quality-of-control measures for the federal government also should include lowering radiation dose as one of their standards, Smith-Bindman said. European countries have done this for more than a decade and doses have fallen there, she said.