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Are We Being Overexposed?

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

CT scans under scrutiny

Medical imaging is only part of the radiation equation, contributing half of the total exposure, according to radiation experts. Background radiation and occupational exposure also are sources. But CT scans are under particular scrutiny because they are being used so frequently—roughly half of the medical imaging increase was linked to CT scans.

Also, CT scans can involve significantly more radiation than some other imaging tests. A CT scan of the abdomen involves a radiation dose about 50 times higher than an abdominal x-ray, according to Brenner.

For Liebross, the cost—$350 out of pocket—and related radiation exposure from her CT scans were a small price to pay for peace of mind. Her lungs looked great. Her heart was plaque-free. “I think the limited amount of radiation exposure was worth finding out the results,” she says.

Radiation exposure guides

So how much radiation exposure is worrisome? To date, researchers have extrapolated from other experiences with radiation, including the cancers that developed among atomic bomb survivors in Japan.

According to the Health Physics Society:

  • A lifetime radiation dose of 100 mSv increases cancer risk by roughly 1 percent. Thus, the average lifetime risk of developing cancer, 42 percent, would be increased to 43 percent.
  • As a rule, 100 mSv equals about 1,000 chest x-rays, 250 mammograms, 50 head CT scans, 13 abdominal or pelvic CT scans, or 10 cardiac nuclear imaging tests.
  • In short, someone who has battled cancer or heart disease and requires repeated CT scans has accumulated more lifetime radiation exposure than someone who only gets periodic mammograms and dental x-rays.

And radiation is only one of many factors that can potentially influence cancer’s growth, says Peter Shields, M.D., deputy director of Georgetown University’s Lombardi Comprehensive Cancer Center.

But patients should still take the initiative and ask their doctor about the need for imaging tests, experts say.

NOTE: Magnetic resonance imaging, MRI, also an expensive technique used with increasing frequency, does not expose patients to radiation.

Charlotte Huff is a Texas-based health and business writer.

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