The rapid growth in use of medical diagnostic imaging, such as CT scans, has led to concern by some people about radiation exposure in adults and the potential for future cancer risk in patients undergoing these tests.

A new study now shows that kids also frequently receive these types of imaging procedures during their routine clinical care. The research highlights the importance of initiatives to ensure that those tests being performed are necessary and use the lowest possible doses of radiation, the scientists said.

Our findings indicate that more awareness about the frequent use of these tests may be needed among care providers, hospitals and parents, said study team member Dr. Adam L. Dorfman, clinical assistant professor of pediatrics and communicable diseases and of radiology at the University of Michigan Medical School. Imaging tests are a critical component of good medical care, but the high number of tests raises questions about whether we are being judicious in our use of the technology.

The results of this study were published online Monday (Dec. 3) in the Archives of Pediatrics and Adolescent Medicine.

Despite widespread discussions about the health hazards of environmental exposures in children, radiation exposure from the frequent use of imaging procedures has received less attention, possibly due to limited contemporary data in younger patients. As such, this study identified 355,088 children under the age of 18 in five large U.S. health care markets to track how often these imaging procedures are used.

The study found that over 400,000 imaging procedures were performed in just 3 years, with 42.5 percent of the children receiving at least one of these procedures and many undergoing multiple tests. The types of tests the investigators considered included everything from routine x-rays that use very low doses of radiation to more advanced tests, like CT scans, that require doses that are greater. Based on these data, the average child in this study population would be expected to receive approximately 7 imaging procedures utilizing radiation by age 18.

The study focused on the numbers and types of procedures that were performed, and did not calculate specific doses of radiation that were received by each child. Data to perform such calculations are limited in children and are part of ongoing work by the team.

What we've tried to do is raise awareness of the issue and start a national dialogue by identifying the overall scope of the problem, Dorfman said. One limitation of this type of analysis is that the clinical appropriateness of the tests could not be determined, he adds.

The next step is to better understand when these tests really add value to care and when they don't, he said.

Among the tests that the investigators considered, CT scans are the most important from the standpoint of radiation exposure. Nearly 8 percent of the children in this study received a CT scan in the 3-year study period, with 3.5 percent of the children receiving more than one. Understanding patterns of utilization of these tests in children is important because children and infants are more susceptible than adults to the risks of radiation exposure, such as future cancers.

Developing tissues in children are more sensitive to radiation and their longer expected life spans also allows additional time for the emergence of detrimental effects, says co-author, Reza Fazel, M.D., M.Sc., a cardiologist at the Emory School of Medicine. Fazel cautions that for any individual child undergoing a single test the risk is typically low.

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, said study co-author Dr. Kimberly E. Applegate of EmoryUniversity. We have to be smarter about how we use tests. For example, children don't always need the same radiation dose during a CT scan to get the same quality of image and information.

Investigators note that each imaging procedure should be guided by the principle of ALARA, or As Low As Reasonably Achievable, which advocates for minimizing radiation doses while still obtaining sufficient clinical information. Applegate, a member of the international Image Gently Campaign, is working with a coalition of health care organizations to raise awareness of the need to adjust radiation doses when imaging children. The Image Gently campaign promotes optimal scanning strategies to lower radiation exposure in children.

Dr. Andrew J. Einstein, a cardiologist at Columbia University and another coauthor of the study, said this study should not deter parents from imaging procedures that may provide clear benefit for their children. It should encourage discussions about the value of each imaging test that is ordered, recognizing that radiation exposure, even in small amounts, may not be risk free.

The research was funded by the National Institutes of Health and other organizations.