Data from the first large-scale study of U.S. population radiation exposure since 1989 show the annual per capita radiation dose increased 5.9 times, from 0.54 millisieverts in 1980 to 3.2 millisieverts in 2006. The collective annual population medical radiation dose increased 7.5 times during that same period, growing from a total of 124,000 sieverts to 930,000 sieverts.

The preliminary findings, presented today by Dr. Fred A. Mettler, Jr., at the NCRP's annual meeting in Arlington, Virginia, focused only on levels of ionizing radiation exposure. They did not contain any recommendations or assess the risks versus benefits of medical radiation, two components the final study may include when it is completed in 2008.

The dramatic increase in medical radiation exposure can be attributed to the proliferation of computed tomography (CT) scans and nuclear medicine procedures, both of which subject patients to high doses of radiation.

1The data Dr. Mettler presented show the number of CT scans done in the United States has grown each of the past 14 years, from 18.3 million scans in 1993 to 62 million scans in 2006. Last year CT scans made up 12 percent of all medical radiation procedures done in the United States but accounted for 45 percent of the U.S. population's collective medical radiation dose.

The study used data from multiple sources including the Virginia health care system, FDA, state radiation programs, large hospitals and claims data from large national employer health care plans to produce the greatest accuracy.

Dr. Mettler said the doses of radiation from these tests can be significantly reduced without reducing diagnostic accuracy, and most physicians are not educated enough on the magnitude of risk associated with increased medical radiation. Dr. Mettler, a member of the NCRP subgroup responsible for the study, and Professor Emeritus in the Department of Radiology at the University of New Mexico School of Medicine, emphasized these were his own conclusions from the data and were not necessarily representative of those of the NCRP.

Mahadevappa Mahesh, a medical physicist at Johns Hopkins University and another member of the NCRP subgroup, said it is important to educate physicians on the dangers of high doses of radiation.

"These tests are now so fast and easy, we have to make sure they are only being used when definitely needed," said Dr. Mahesh, a member of the American Association of Physicists in Medicine, which in turn is a member society of the American Institute of Physics.

He emphasized the value of modern medical radiation procedures far outweighs the potential risks involved.

"The benefits of these tests are really high," Dr. Mahesh said. "We just need to pay attention to the dose issue."

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