International variation in radiation dose for computed tomography examinations: prospective cohort study.

To determine patient, institution, and machine characteristics that contribute to variation in radiation doses used for computed tomography (CT). Prospective cohort study. Data were assembled and analyzed from the University of California San Francisco CT International Dose Registry. Standardized data from over 2.0 million CT examinations of adults who underwent CT between November 2015 and August 2017 from 151 institutions, across seven countries (Switzerland, Netherlands, Germany, United Kingdom, United States, Israel, and Japan). Mean effective doses and proportions of high dose examinations for abdomen, chest, combined chest and abdomen, and head CT were determined by patient characteristics (sex, age, and size), type of institution (trauma center, care provision 24 hours per day and seven days per week, academic, private), institutional practice volume, machine factors (manufacturer, model), country, and how scanners were used, before and after adjustment for patient characteristics, using hierarchical linear and logistic regression. High dose examinations were defined as CT scans with doses above the 75th percentile defined during a baseline period. The mean effective dose and proportion of high dose examinations varied substantially across institutions. The doses varied modestly (10-30%) by type of institution and machine characteristics after adjusting for patient characteristics. By contrast, even after adjusting for patient characteristics, wide variations in radiation doses across countries persisted, with a fourfold range in mean effective dose for abdomen CT examinations (7.0-25.7 mSv) and a 17-fold range in proportion of high dose examinations (4-69%). Similar variation across countries was observed for chest (mean effective dose 1.7-6.4 mSv, proportion of high dose examinations 1-26%) and combined chest and abdomen CT (10.0-37.9 mSv, 2-78%). Doses for head CT varied less (1.4-1.9 mSv, 8-27%). In multivariable models, the dose variation across countries was primarily attributable to institutional decisions regarding technical parameters (that is, how the scanners were used). CT protocols and radiation doses vary greatly across countries and are primarily attributable to local choices regarding technical parameters, rather than patient, institution, or machine characteristics. These findings suggest that the optimization of doses to a consistent standard should be possible. Clinicaltrials.gov NCT03000751.

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Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf and declare: support from the US National Institutes of Health; Patient-Centered Outcomes Research Institute; Centers for Disease Control and Prevention; and the University of California Office of the President, Center for Health Quality and Innovation for the submitted work; RS-B reports grants from the US National Institutes of Health, Patient-Centered Outcomes Research Institute, Centers for Disease Control and Prevention, and the University of California Office of the President, is on a scientific advisory board, and has given talks for Bayer Healthcare; BND is on a scientific advisory board and has given talks for Bayer Healthcare; AJE has served as a consultant to GE Healthcare, and Columbia University has received support for other research from Toshiba America Medical Systems; MD reports grants and personal fees from Bayer Healthcare, grants and personal fees from Siemens Healthcare, grants from Philips Healthcare, personal fees from Cook Medical, outside the submitted work; AS reports non-financial support and is on Bayer Healthcare scientific advisory board; JS has given talks for Bayer Healthcare; JEW reports institutional grants from Agfa, Bard, Bayer, GE, Optimed, Philips, Siemens, personal fees (speaker’s bureau) from Bayer, Siemens, outside the submitted work; DLM is on an advisory board for Hologic; the remaining authors have nothing to disclose.