OA137] Adult radiation doses for computed tomography (CT) from an international dose registry

Abstract

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.