In reply: We thank Lavoipierre for his response to our article.1 He brings up two main points. First, he suggests that our statement that newer computed tomography (CT) scanners emit more radiation is incorrect.2 We acknowledge that actual absorbed doses for exactly the same imaging are lower with newer scanners, but the total exposure of the population may be increasing. In the United States, between 1993 and 2006, the annual number of CT scans increased by more than 10% per year, while the population increased less than 1% per year.3 If some scans are unnecessary for safe clinical care, then unsafe radiation exposure is a consequence.
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