WEDNESDAY, June 6 (HealthDay News) -- Children who undergo CT scans of the head may raise their risk of developing brain cancer or leukemia later in life, a new study says.
Although multiple CT scans could triple the risk, the absolute risk remains small -- one case in 10,000 scans of the head, the researchers said.
"We have shown small increased risks associated with the radiation exposures from CT," said study co-author Louise Parker, from the Canadian Cancer Society and a professor of medicine and pediatrics at Dalhousie University in Halifax, Nova Scotia.
"As long as CT is used only where justified, then the benefits of CT, a potentially lifesaving modality, will almost certainly outweigh the risks," she said.
Lead study author Amy Berrington de Gonzalez, from the U.S. National Cancer Institute, said this study is the first to look at the actual cancer risk of radiation from CT scans.
"All the previous studies about the potential risk of CT scans have been theoretical studies using models from other radiation-exposed populations," she said. Specifically, they studied the results of radiation exposure after atom bombs were dropped on Japan during World War II.
For the new study, researchers collected data on almost 180,000 British patients under age 22 who had CT scans between 1985 and 2002. They looked at cases of leukemia, brain tumors, how many scans were done and radiation dose absorbed by the brain and bone marrow.
Seventy-four patients developed leukemia, and 135 developed brain cancer. The researchers calculated that the relative risk for leukemia increases 0.036 for every extra milli-Gray (mGy) used, and the risk for brain tumors, 0.023 per additional mGy.
Using these data, they further calculated that one head CT scan before age 10 would result in one excess case of leukemia and one excess brain tumor per 10,000 patients in th
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