The average child undergoes nearly seven imaging scans involving radiation before turning 18, according to estimates from one of the first studies to examine data from hundreds of thousands of U.S. children to gauge the impact of the boom in medical imaging.

The study, published online Monday in Archives of Pediatrics and Adolescent Medicine, found around 42 percent of children in the three-year study period received an imaging exam with radiation, and nearly a quarter received two or more tests.

Although most underwent routine X-ray exams, which use low amounts of radiation, nearly one in 10 got a CT scan, which uses much greater doses. And nearly one in 30 received multiple CT scans over the study period.
Although the risk of any one imaging exam to children is usually extremely low, children are more at risk from radiation as their longer lifespans mean they have more time to develop radiation-induced cancers, the researchers noted; plus, their developing tissue is more sensitive to radiation's effects.

"Our findings indicate that more awareness about the frequent use of these tests may be needed among care providers, hospitals and parents," said study author Dr. Adam L. Dorfman, clinical assistant professor of pediatrics and communicable diseases and of radiology at the University of Michigan Medical School in Ann Arbor, in a statement.

For the study, the researchers identified 355,088 children under age 18 in health care markets in Arizona, Texas, Florida and Wisconsin, who had received more than 400,000 imaging exams, excluding dental X-rays, between 2005 and 2007.

However, the authors were quick to note that the study methods prevented them from calculating specific doses delivered to children and from judging the clinical appropriateness of the exams.

"Of course, there is immense life-saving value in medical imaging, so our study doesn't suggest at all that these tests shouldn't be used in children," Dr. Kimberly E. Applegate, a co-author of the study who helps oversee safety at the radiology department of Emory University, said in a statement.

Applegate, who participates in the Image Gently campaign, a coalition of groups including the American College of Radiology that seeks to raise awareness of issues surrounding childhood imaging, noted that children don't always need the same radiation dose as adults to get the same quality information.

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