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New Campaign to Curb Radiation From CT Scans

Experts Hope to Reduce Use of Excessive Imaging Tests
By
WebMD Health News
Reviewed by Laura J. Martin, MD

Dec. 2, 2010 (Chicago) -- Embracing the medical creed to "do no harm," experts today outlined a series of steps aimed at curbing exposure to unnecessary radiation during imaging tests, most notably CT scans.

Radiation, particularly repeated high-dose exposures, has been linked to a small increased risk of cancer years later.

Called "Image Wisely," the new campaign aims to ensure "we use the right procedure at the right dose for the right patient," panel member William R. Hendee, PhD, distinguished professor of radiology, radiation oncology, biophysics, and bioethics at the Medical College of Wisconsin in Milwaukee, tells WebMD.

Speaking at the annual meeting of the Radiological Society of North America, the expert panel says there has been a sevenfold increase in the use of radiation-based imaging in the past 25 years.

Also, a study presented at the meeting suggests that the average person is being exposed to higher doses of radiation from X-rays, angiography, and CT scans than in the past. But another study suggests that the cancer risk from CT scans may be overestimated, at least in the elderly.

Increase in Imaging

Despite the growth in imaging tests over the past three decades, there has not been a similar rise in cancer cases or deaths in the U.S., says panel member Christoph Wald, MD, PhD, executive vice chairman of the department of radiology at the Lahey Clinic in Burlington, Mass., and associate professor of radiology at Tufts University in Boston.

Nevertheless, radiation is frequently portrayed negatively in the press, with headlines in newspapers and on broadcast media screaming out its risks, Wald says.

Hendee says cancer risks have largely been estimated using a National Academy of Sciences study of Japanese survivors of atomic bombs dropped on Hiroshima and Nagasaki in 1945. People at the far edge of those blasts who absorbed about 50 millisievert (mSv) of radiation appear to have an increased lifetime cancer risk of 0.05%, he says.

A series of CT exams might expose a person to that much radiation, Hendee says. Since the lifetime risk of cancer for the average American’s is about 33%, the 0.05% increased risk associated with that exposure is basically negligible on the individual level, he says. But from a public health point of view for the entire population, it could be noteworthy, he says.

According to the medical literature, 50 to 100 mSv of radiation is associated with "some increase in cancer incidence," according to Pat Basu, MD, of Stanford University. He presented the new study on cancer risks in the elderly, but was not on the panel.

By comparison, 10 continental round-trip airplane flights expose a passenger to 1 mSv of radiation and an astronaut is exposed to about 200 mSv per year, Basu says. Health care workers are limited to 20 mSv of radiation per year, he says.

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