LOS ANGELES — As many as two-thirds of adults underwent a medical test in the last few years that exposed them to radiation and, in some cases, a potentially higher risk of cancer, a study in five areas of the U.S. suggests.
It is the latest big attempt to measure how much radiation Americans are getting from sometimes unnecessary medical imaging.
Though the annual average radiation exposure from X-rays, CT scans and other tests was low, researchers found about 20 percent were exposed to moderate radiation doses and 2 percent were exposed to high levels. “Super X-rays” to check for heart problems accounted for nearly a quarter of the radiation people received.
“Given the growing use of medical-imaging procedures, our findings have important implications for the health of the general population,” the researchers reported in today’s New England Journal of Medicine.
The study did not directly address whether medical imaging is being overused, but some doctors are concerned that advanced tests such as CT scans are being overprescribed and that evidence of their value in certain situations is lacking.
“CT scans produce beautiful pictures, but they generate a huge amount of radiation compared with a standard X-ray,” said Dr. Michael Lauer of the National Heart, Lung and Blood Institute, who was not part of the research.
Some insurers, citing spiraling costs and safety concerns, are requiring pre-authorizations and setting other limits before patients can receive these scans.
For their study, researchers led by Emory University analyzed insurance claims from 952,420 people between ages 18 and 64 to determine how many had an imaging test and the estimated radiation dose. All were covered by UnitedHealthcare in five regions: Arizona, Dallas, Wisconsin and two areas of Florida.
Nearly 70 percent had at least one medical test between 2005 and 2007 that exposed them to radiation doses double what would be expected from natural sources in the environment, the researchers said.
High radiation exposure is a risk factor for cancer. Many years usually pass between radiation exposure and the appearance of cancer.
Far more women had imaging procedures than men — 79 percent versus 58 percent. This is a concern because women live longer and face a higher risk of developing radiation-induced cancer.
Dr. James Thrall, chief radiologist at Massachusetts General Hospital, said a big limitation of the study was the lack of information about why the tests were done. Without it, he said, it’s impossible to know whether a test was medically necessary.
“There’s a risk that people who need a life-saving or life-improving imaging procedure might not get one” because of radiation worries, said Thrall, who is also chairman of the American College of Radiology’s board of chancellors.
