In 2014, an estimated 81.2 million computed tomographic (CT) scans were performed in the United States, including 12.6 million chest examinations, and overall approximately 52% of these were preformed with contrast material (1). CT scans can save lives and can enable unnecessary surgical procedures to be avoided; however, the very high levels of use, particularly in the United States, have raised questions about the associated risks and costs. One potential risk is the small possibility the patient will develop a radiation related cancer. Two large cohorts of children who underwent CT provided some of the first evidence of a possible link to subsequent cancer risk (2,3). These findings still need additional replication, and deeper assessment of potential biases is ongoing; however, the size of risk was broadly consistent with the Japanese atomic bomb studies, a finding that further supports the linear no-threshold assumption for radiation protection purposes (4).