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ImportanceComputed tomography (CT) radiation doses vary across institutions and are often higher than needed.ObjectiveTo assess the effectiveness of 2 interventions to reduce radiation doses in patients undergoing CT.Design, Setting, and ParticipantsThis randomized clinical trial included 864 080 adults older than 18 years who underwent CT of the abdomen, chest, combined abdomen and chest, or head at 100 facilities in 6 countries from November 1, 2015, to September 21, 2017. Data analysis was performed from October 4, 2017, to December 14, 2018.InterventionsImaging facilities received audit feedback alone comparing radiation-dose metrics with those of other facilities followed by the multicomponent intervention, including audit feedback with targeted suggestions, a 7-week quality improvement collaborative, and best-practice sharing. Facilities were randomly allocated to the time crossing from usual care to the intervention.Main Outcomes and MeasuresPrimary outcomes were the proportion of high-dose CT scans and mean effective dose at the facility level. Secondary outcomes were organ doses. Outcomes after interventions were compared with those before interventions using hierarchical generalized linear models adjusting for temporal trends and patient characteristics.ResultsAcross 100 facilities, 864 080 adults underwent 1 156 657 CT scans. The multicomponent intervention significantly reduced proportions of high-dose CT scans, measured using effective dose. Absolute changes in proportions of high-dose scans were 1.1% to 7.9%, with percentage reductions in the proportion of high-dose scans of 4% to 30% (abdomen: odds ratio [OR], 0.82; 95% CI, 0.77-0.88; P P = .03; combined abdomen and chest: OR, 0.49; 95% CI, 0.41-0.59; P P P P P Conclusions and RelevanceFor imaging facilities, detailed feedback on CT radiation dose combined with actionable suggestions and quality improvement education significantly reduced doses, particularly organ doses. Effects of audit feedback alone were modest.Trial RegistrationClinicalTrials.gov Identifier: NCT03000751

Purpose To contribute to the creation of CT radiation dose benchmarks for adults (>=15 years). We report the distribution of radiation dose metrics based on CT scans submitted in 2017 to a large international dose registry comprised of 139 institutions from 7 countries. The registry was supported through the US National Institutes of Health (NIH) and Patient Centered Outcomes Research Institute (PCORI). Methods We describe median (target) and 75th percentile (benchmark) doses for CT dose index volume (CTDIvol) and dose length product (DLP) by anatomic area across all institutions. Each institution was weighted equally when calculating targets and benchmarks. Results The US and Europe contributed 714,297 and 85,686 adult CT scans, respectively, during 2017, including examinations of the head (33%), chest (25%) abdomen (37%) and combined chest-abdomen (CAP) (5%). CTDIvol target (50%) and benchmark (75%) values (in mGy), respectively, in the US were: head (44 and 54), chest (9 and 13), abdomen (11 and 16), and CAP (10 and 14). Corresponding values in Europe were 4–52% lower: head (38 and 47), chest (4 and 7), abdomen (7 and 11), and CAP (9 and 14). Corresponding DLP values (in mGy-cm) for the US were: head (841 and 1075), chest (338 and 560), abdomen (669 and 1081), and CAP (918 and 1416). Corresponding values in Europe were 18–52% lower: head (685 and 789), chest (163 and 334), abdomen (425 and 675), and CAP (670 and 1045). The results changed minimally after accounting for patient size using circumference of the body part scanned. For CTDIvol, no value changed more than 2 mGy and for DLP no value changed more than 100 mGy-cm. Similar usage of multi-phase scanning in Europe (23%) and the US (22%) does not explain the large differences in DLP. Conclusions Dose metrics reported in a large number of patients can contribute to the creation of representative benchmarks that can be used for dose optimization efforts and institutional evaluation of CT radiation doses to know if their doses routinely exceed these benchmarks. Additional work should be undertaken to explore the reasons that doses are higher in the US than Europe.

Purpose To summarize data on radiation doses collected from pediatric ( 15 years) CT examinations that can contribute to improving existing reference levels. Methods As part of a US National Institutes of Health (NIH) and Patient Centered Outcomes Resaerch Institute (PCORI) funded study, we created a CT radiation dose registry that includes pediatric ( 15 years) scans from 139 facilities in calendar year 2017. We describe, for separate anatomic regions, median (”target”) and 75th percentile (”benchmark”) values of CT dose index volume (CTDIvol) and dose length product (DLP) for US and European institutions separately. We further stratified pediatric doses by age group into 10 levels. Results Results include 17168 CT scans of the head (65%), chest (11%) abdomen (22%) and chest-abdomen-pelvis (CAP) (2%) performed in children across Europe and the US. In European pediatric scans, the target and benchmark CTDIvol values (in mGy) were: head (21.02 and 33.07), chest (1.51 and 2.30), abdomen (3.06 and 4.42). In US pediatric scans, the benchmark CTDIvol values were: head (22.79 and 30.29), chest (2.48 and 4.61), abdomen (4.63 and 6.19). In European pediatric scans, the target and benchmark DLP values (in mGy-cm) were: head (431.70 and 565.70), chest (38.29 and 63.96), abdomen (114.06 and 162.63). In US pediatric scans, the benchmark DLP values were: head (388.00 and 568.20), chest (64.90 and 144.07), abdomen (191.60 and 296.10). With the exception of head scans, European doses appear to be much lower than US doses. Similar usage of multi-phase scanning in Europe (13%) and the US (12%) does not explain the large differences in DLP. For benchmark chest scans in the US, the dose ranged by age from 2.0 to 6.7 mGy; for Europe 1.7 to 4.6. Similar variations occur in other anatomic regions. Conclusions Dose metrics from a large sample, multi-institution, multi-national registry can contribute to the creation of representative pediatric benchmarks that can be used for dose optimization and inter-institution comparisons. Pediatric doses are generally lower among European institutions compared to US institutions. For both US and European pediatric scans, we generally found a doubling of dose by age within each anatomical region.