Radiation, CT, and Children: The Simple Answer Is … It's Complicated

Abstract

Donald P. Frush, MD Why are we still discussing radiation exposure in children from computed tomographic (CT) examinations? There are several reasons. First, CT exposure to the population in the United States has substantially increased. On March 3, 2009, the National Council on Radiation Protection and Measurements released summary statements from report 160 that indicated that the U.S. population is currently exposed to approximately seven times the amount of ionizing radiation from medical imaging than it was in the first half of the 1980s (1). Background sources account for 50% of the total, but medical imaging now accounts for 48%. (Consumer and occupational exposures make up the remaining 2%.) CT is responsible for the majority of the dose contribution from medical imaging and for about 25% of the total exposure to the U.S. population. The scope of increased radiation from medical imaging is not simply an issue in the United States. This past June, in Busan, South Korea, the World Health Organization International Conference on Children’s Health and the Environment included a preconference workshop, “Towards a Safer Use of Radiation in Paediatrics,” as part of an ongoing Global Initiative on Radiation Safety in Health Care Settings, in addition to time during conference plenary sessions for discussion of radiation exposure in children. Moreover, and closer to this readership, five articles in the April 2009 issue of Radiology deal specifically with radiation dose, dose risk, or dose reduction strategies (2–6). Contrast this to the Radiology issue 10 years ago in April, where there were no articles dealing specifically with this topic. This ongoing focus on radiation is in part because of the specter of cancer. In November 2007, the New England Journal of Medicine published a review article by Brenner and Hall (7). One conclusion was that up to 2% of all cancers in the United States could be because of CT radiation exposure (7). While the conclusions are debatable, radiation awareness and management are still fundamental principles (ie, as low as reasonably achievable) in our profession. We recognize our responsibilities in radiation protection, but why do we find ourselves continuing to be confronted with CT radiation exposure, particularly in children? This is where it starts to get complicated. Utilization is a complex issue. There are many factors that drive the use of CT. These include scientific growth and development (both technologic advances and applications, particularly outcome based); empiric influences (eg, move to the defensive use of CT [8] or personal experiences); industry marketing (the must-have latest technical advancements); use outside of radiology and embedded issues with self-referral (9); forces that drive both increase and decrease of CT use through the media; and, finally, public sentiment and pressures. Even when the use is appropriate, the choice of techniques can also get complicated. Rapid evolution in scanner technology often outpaces our ability to understand appropriate techniques and applications (eg, just how and when should we use dual-energy CT in children?). Tube current modulation, which would appear to be a straightforward tool for dose reduction, can also be challenging (10), especially in children. In pediatrics, weight ranges, which may vary in orders of magnitude from less than 1 kg to more than 100 kg, require a greater understanding of CT technology and protocols. Increasing numbers of detector rows, changes in detector technology and efficiency, alterations in source to isocenter distances with corresponding dose index changes for tube current, and dual-source and dualenergy technology conspire to create a complex landscape in which to try to do the right thing with respect to appropriate radiation dose and image quality in children. And when what we do is comPublished online 10.1148/radiol.2521090661