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Are We Being Overexposed?

As Americans take more imaging tests, how much radiation is too much? And at what cost?

Imaging tests can play a crucial role in diagnosing cancer, heart blockages, and other diseases. Before agreeing to any test, however, patients should weigh the risks and benefits of their particular situation, physicians advise.

Luckily, as adults age, the very small cancer risk associated with radiation exposure gets even smaller, says David Brenner, director of the Center for Radiological Research at Columbia University Medical Center. It takes most radiation-induced cancers 10 to 20 years to develop in adults, says Brenner, one of the country’s foremost authorities on low-dose radiation and cancer risk. Older adults are more likely to have medical problems that can be identified by a CT scan or another test, he says, but “you don’t want to have a CT scan unless there is a very good reason for doing so.”

Other top experts agree.

“In a way, the worst radiation exposure is from a test that wasn’t necessary in the first place,” says James Thrall, M.D., chair of the board of chancellors at the American College of Radiology. “That’s just a tragedy. What compounds the tragedy is it’s going to cost the individual money on top of the unnecessary radiation exposure. And it’s going to cost society money.”

What’s driving many tests

Experts say physicians are prescribing more imaging tests. They point specifically to “physicians with a financial stake in [imaging] facilities who refer patients to those facilities,” says David Schauer, executive director of the National Council on Radiation Protection and Measurements. Indeed, physicians who own their own imaging equipment are more likely to order imaging tests than other doctors, according to a report in June by the Medicare Payment Advisory Commission.

As part of health care reform legislation, Congress is considering a measure that would prohibit doctors from referring their own patients to their imaging machines. Currently doctors are barred from referring Medicare patients for services in which they have a financial interest, but CT scans are exceptions.

In a study last year, Stanford University’s Laurence Baker found that each new CT scanner in service prompted an additional 2,224 CT tests per year, adding $685,000 to Medicare costs.

But financial interest isn’t the only driving force behind the growing number of tests. So is defensive medicine, to some degree. One out of every five x-rays and 28 percent of all CT scans are ordered because of malpractice fears, according to the Massachusetts Medical Society, which surveyed 850 doctors.

But even as the number of tests increases, clinicians are not necessarily savvy about the degree of radiation involved, which can range from lower levels with x-rays and mammograms to higher levels with CT scans and barium enemas. In a recent survey involving physicians at a teaching hospital, nearly 63 percent underestimated the radiation exposure of an abdominal CT scan. And just 20 percent said they discussed radiation with patients.

FDA warnings

Marketing also can spur demand. The Food and Drug Administration advises against full-body scans for patients who have no symptoms. It says the risks related to radiation and unnecessary follow-up tests outweigh any potential benefits. In May, federal officials decided that Medicare should not cover virtual colonoscopies, when they weighed the medical benefits against potential risks, including radiation exposure.

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