Objectives To quantify trends in pediatric computed tomography (CT) use and associated radiation exposure and cancer risk. Design Retrospective observational study. Setting Seven US healthcare systems. Participants CT use was evaluated in children <15 years from 1996-2010, including 4,857,736 child-years of observation. Radiation doses were calculated for 744 CT scans performed between 2001-2011. Outcome Measures Rates of CT use, organ and effective doses, and projected lifetime attributable cancer risks. Results CT use doubled in children <5 years and tripled in children 5-14 between 1996-2005, stabilized until 2007, then declined. Effective doses varied from 0.03-69.2mSv per scan. An effective dose of ≥20mSv was delivered by 14-25% of abdomen/pelvis CTs, 6-14% of spine CTs, and 3-8% of chest CTs. Projected lifetime attributable risks of solid cancer were higher in younger patients and girls, and for abdomen/pelvis and spine CTs. In girls, a radiation-induced solid cancer is projected to result from every 300-390 abdomen/pelvis CTs, 330-480 chest CTs, and 270-800 spine CTs, depending on age. Leukemia risk was highest for head CTs in children <5 at 1.9/10,000. Nationally, 4 million pediatric CTs of the head, abdomen/pelvis, chest, or spine performed each year are projected to cause 4870 future cancers. Reducing the highest 25% of doses to the median might prevent 43% of these cancers. Conclusions Increased use of pediatric CT combined with wide variability in radiation doses has resulted in many children receiving a high-dose examination. Dose-reduction strategies targeted to the highest quartile of doses could dramatically reduce the number of radiation-induced cancers.

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