Radiation From Medical Scans Soaring

Americans' exposure to radiation from medical procedures has exploded over the past few decades, to six times the level of 1980, a new report shows.

In 2006, almost 380 million diagnostic and interventional radiological procedures were performed in the United States, on top of 18 million nuclear medicine examinations.

"Back in about 1980, 15 percent of radiation that the U.S. population got was from medicine and the rest was predominantly from natural background radiation," noted Dr. Fred Mettler Jr., U.S. Representative to the United Nations Scientific Committee on the Effects of Atomic Radiation and a professor of radiology at the University of New Mexico in Albuquerque. "In the last 20 years, medical exposure has gone up between 600 and 700 percent from what it was, and it is now the biggest source of radiation to the U.S. population."

"The issue," Mettler continued, "is that this is a controllable source. We regulate the effluent from nuclear power plants so the public doesn't get exposure but medical exposure is essentially unregulated. The largest source in the U.S. is essentially unregulated, and it's up to your family doctor or any other doctor to hand it out."

Mettler is lead author of a paper appearing in the November issue of Radiology that summarizes the conclusions of two previous reports on radiation sources in the U.S. Those reports were issued by the U.S. National Council on Radiation Protection and Measurements and the United Nations Scientific Committee on Effects of Atomic Radiation.

The findings are in line with previous studies, one of which attributed up to two percent of all cancers to CT scans alone and another which concluded that cumulative exposure to radiation from CT scans increases the risk for malignancy by as much as 12 percent.

The last comprehensive assessment of radiation exposure was conducted in 1980-1982, a veritable eternity by medical and scientific standards.

"We needed to get a grip on how much radiation the U.S. was getting and where it was coming from," Mettler said.

In the intervening years, the number of procedures performed has risen "by leaps and bounds," he said. "The biggest chunk of that is CT scanning, which has been growing at better than 10 percent a year while the U.S. population is growing at less than 1 percent."

Widely used as a diagnostic tool, CT scans provide detailed images of organs, allowing more accurate diagnoses of conditions such as cancer. But CT involves a higher radiation dose than most other imaging tests. According to this paper, CT provides half of the country's total radiation dose, even though it represents only 17 percent of total procedures.

Emergency room physicians may be at the epicenter of the surge in scan use, Mettler said. "Twenty-five to 40 percent of CT scans are ordered out of the ER," he noted. "The emergency physicians are in a tough box because they're worried about getting sued. And they tend to get patients who they haven't seen before. This is a one-time walk-in and their mantra is, 'We can't afford to miss anything.'"

Of course, the trend is not limited to the U.S., although it may be more extreme here. Globally, the per-capita annual dose from medicine has doubled in the past decade or so.

Still the U.S. leads the pack, with 12 percent of all radiologic procedures and half of nuclear medicine procedures performed here.

"We have a little under 5 percent of the world's population and 25 percent of X-ray studies in the world and double and triple that of other developed countries," Mettler said. "Nobody thought about how much radiation goes with this."

But not all of uptick in scans has been unnecessary, said Dr. Robert Zimmerman, executive vice chair of radiology at Weill Cornell Medical Center in New York City.

"We don't really know how much of it is overuse. We do know some of it is overutilization, but CT is a valuable imaging modality. CT is a great test. There's no question that in the appropriate cases it's going to save lives."

There are things radiologists can do to curb its use, including reducing the doses, while manufacturers are working on new and improved machines, Zimmerman said.

Physicians can also tailor their use, thinking twice about using this type of technology in children, who are more sensitive to radiation and have longer to develop side effects.

"When I get a call for a CT scan, my first question is, 'How old is the patient?' If it's 40 or under my antennas go up and if they're 70 my antennas don't get so excited. Mostly my idea is a CT might be a good thing but you would like to think about radiation beforehand," Mettler said. "There's a lot of stuff going on now that isn't justified. Nobody's ever shown that many of these things we do make a difference in outcome."

SOURCES: Fred A. Mettler Jr., M.D., U.S. representative to the United Nations Scientific Committee on the Effects of Atomic Radiation, and professor, radiology, University of New Mexico, Albuquerque; Robert Zimmerman, M.D., executive vice chair, radiology, Weill Cornell Medical Center, New York City; November 2009 Radiology
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