Too Much Radiation From Medical Imaging?
Researchers Say Patients Need to Weigh Risks vs. Benefits of Imaging Tests
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
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
"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
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
- The highest radiation exposures occurred among women and older
- 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
Myocardial perfusion imaging for heart disease delivers about 15 mSv per
Value of Some Medical Imaging Unclear
In a perspective published with the study, cardiologist Michael S. Lauer,
MD, of the National Heart Lung and Blood Institute (NHLBI) presented the
hypothetical case of a 58-year-old man named Jim with risk factors for heart
disease who has an inconclusive nuclear stress test followed by another
commonly used imaging test known as CT angiography, which also fails to confirm
The two tests would result in more than 20 mSv of radiation exposure.