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Too Much Radiation From Medical Imaging?

Researchers Say Patients Need to Weigh Risks vs. Benefits of Imaging Tests
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WebMD Health News
Reviewed by Louise Chang, MD

Aug. 26, 2009 -- As many as 4 million adults in the U.S. under the age of 65 are being exposed to high, potentially cancer-causing levels of radiation from medical imaging tests of unproven value, according to a new government-funded study.

Analysis of insurance claims for close to 1 million non-elderly adults found that roughly two-thirds had at least one medical imaging test resulting in radiation exposure and one-fifth were exposed to moderate-to-high doses of radiation during the study period.

Nuclear imaging (often done to check for heart disease) and computed tomography (CT) scans delivered the most radiation.

An earlier study in 2007 estimated that as many as 2% of cancers in the U.S. are caused by radiation exposure from CT-related imaging alone.

The new study appears in this week's New England Journal of Medicine.

"We don't want to scare people and have them refuse necessary procedures, but physicians and patients need to be aware that radiation is not benign," study researcher Reza Fazel, MD, of Atlanta's Emory University School of Medicine, tells WebMD. "Our study shows that a lot of people are getting high doses of radiation."

Government estimates suggest that per capita radiation doses in the U.S. have risen sixfold since the early 1980s as a result of greater utilization of medical imaging tests performed to diagnose and monitor a wide range of diseases.

The study shows that:

  • CT scans and nuclear imaging accounted for three-fourths of radiation exposure, with nuclear stress tests, also known as myocardial perfusion imaging, identified as the procedure accounting for the largest single radiation exposure. 
  • The highest radiation exposures occurred among women and older adults. 
  • Imaging-associated exposures among young adults were not insignificant. Thirty percent of men and 40% of women with high exposure per year in the study were under the age of 50. 
  • 80% of radiation exposures occurred among non-hospitalized patients.

Radiation exposure is commonly measured in millisieverts (mSv). The average person in the U.S. can expect to receive no more than 3 mSv of exposure per year from naturally occurring background radiation. An exposure of greater than 20 mSv is considered high, while greater than 3 mSv to 20 mSv is considered moderate.

Myocardial perfusion imaging for heart disease delivers about 15 mSv per test.

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