CONCISE CLINICAL REVIEW Monitoring Cystic Fibrosis Lung Disease by Computed Tomography Radiation Risk in Perspective Wieying Kuo 1,2 , Pierluigi Ciet 1,2,3 , Harm A. W. M. Tiddens 1,2 , Wei Zhang 4 , R. Paul Guillerman 5 , and Marcel van Straten 2 1 Department of Pediatric Pulmonology, Erasmus University Medical Center-Sophia Children’s Hospital, and 2 Department of Radiology, Erasmus University Medical Center, Rotterdam, The Netherlands; 3 Department of Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts; and 4 Outcomes and Impact Service, Texas Children’s Hospital, and 5 Department of Pediatric Radiology, Baylor College of Medicine, and Texas Children’s Hospital, Houston, Texas Abstract Computed tomography (CT) is a sensitive technique to monitor structural changes related to cystic fibrosis (CF) lung disease. It detects structural pulmonary abnormalities such as bronchiectasis and trapped air, at an early stage, before they become apparent with other diagnostic tests. Clinical decisions may be influenced by knowledge of these abnormalities. CT imaging, however, comes with risk related to ionizing radiation exposure. The aim of this review is to discuss the risk of routine CT imaging in patients with CF, using current models of radiation-induced cancer, and to put this risk in perspective with other medical and nonmedical risks. The magnitude of the risk is a complex, controversial matter. Risk analyses have largely been based on a linear no-threshold model, and excess relative and excess absolute risk estimates have been derived mainly from atomic bomb survivors. The estimates have large confidence intervals. Our risk estimates are in concordance with previously reported estimates. A large proportion of radiation to which humans are exposed is from natural background sources and varies widely depending on geographical location. The risk differences due to variation in background radiation can be larger than the risks associated with CF lung disease monitoring by CT. We conclude that the risk related to routine usage of CT in clinical care is small. In addition, a life-limiting disease, such as CF, lowers the risk of radiation-induced cancer. Nonetheless, the use of CT should always be justified and the radiation dose should be kept as low as reasonably achievable. Keywords: cystic fibrosis; radiation dose–response relationship; risk assessment methods; child; X-ray computed tomography adverse effects The number of computed tomography (CT) scans performed in the United States has increased by 600% over the past 20 years (1–3). In 2007, nearly 70 million CT procedures were performed in the United States, of which 7 million were performed in the pediatric population (4). Since 2007, CT usage in pediatrics has plateaued or even declined in some locales, likely related to multiple factors including economic cost constraints and increased awareness of cancer risks in the pediatric population, but the technique is still in frequent use (5, 6). A downside of CT imaging is that it involves exposure to ionizing radiation. ( Received in original form November 28, 2013; accepted in final form April 3, 2014 ) Supported by the Dutch Cystic Fibrosis Foundation and the Scientific Foundation Sophia Children’s Hospital, which have given unconditional grants for the research related to this manuscript. Author Contributions: W.K. is the primary investigator of this concise clinical review. She made substantial contributions to conception and design, acquisition of literature, analysis, and interpretation of the literature. P.C. has made substantial contributions to analysis and interpretation of the literature. He has revised the submitted article critically and has provided final approval of the version to be published. H.A.W.M.T. has made substantial contributions to conception and design, and interpretation of the literature. He has drafted and revised the submitted article critically and has provided final approval of the version to be published. W.Z. has made substantial contributions to the analysis. She has revised the submitted article critically and has provided final approval of the version to be published. R.P.G. has made substantial contributions to conception and design, and interpretation of the literature. He has drafted and revised the submitted article critically and has provided final approval of the version to be published. M.v.S. is the senior investigator for this concise clinical review. He made substantial contributions to conception and design, interpretation of data, has revised the submitted article critically, and has provided final approval of the version to be published. He is identified as the guarantor of the review, taking responsibility for the integrity of the work as a whole, from inception to published article. Correspondence and requests for reprints should be addressed to Marcel van Straten, Ph.D., Erasmus MC, ’s-Gravendijkwal 230, 3015 CE Rotterdam, The Netherlands. E-mail: marcel.vanstraten@erasmusmc.nl CME will be available for this article at www.atsjournals.org Am J Respir Crit Care Med Vol 189, Iss 11, pp 1328–1336, Jun 1, 2014 Copyright © 2014 by the American Thoracic Society Originally Published in Press as DOI: 10.1164/rccm.201311-2099CI on April 3, 2014 Internet address: www.atsjournals.org 1328 American Journal of Respiratory and Critical Care Medicine Volume 189 Number 11 | June 1 2014