A Decade of Change In Adult CT Radiation Doses: 2025 U.S. Diagnostic Reference Levels for Common CT Examinations
Abstract
Purpose
To update U.S. national adult CT DRLs and ADs using 2025 data and to demonstrate a scalable, acquisition-level, size-normalized framework for generating timely and clinically relevant national benchmarks.
Methods
This retrospective observational study analyzed approximately 5.2 million adult CT acquisitions performed January 1 through December 31, 2025, across 592 U.S. facilities using the Imalogix radiology optimization platform. Ten CT examination categories matching the prior study were mapped using standardized RadLex Playbook identifiers. Dose metrics (CTDIvol, DLP) were extracted from dose structured reports and normalized at the acquisition level to enable assessment of multiphase examinations. Patient size was represented by attenuation-based water-equivalent diameter (WED) derived from axial images with automated truncation detection and correction, and size-specific dose estimates (SSDE) were calculated per AAPM Task Group guidelines. Facility-level median dose metrics were computed by size category, and ADs and DRLs were defined as the 50th and 75th percentiles, respectively, of facility medians in accordance with ICRP Publication 135. Results were compared with U.S. national benchmarks derived from 2014 examinations.
Results
Relative to 2014 benchmarks, national CTDIvol DRLs decreased by an average of 21.8% across ten adult CT examination categories, while CTDIvol ADs decreased by 9.3%. The largest relative reductions were observed for thoracic and abdominopelvic examinations. Across all torso examinations, CTDIvol, SSDE, and DLP demonstrated consistent size dependence, with higher dose metrics observed in larger WED categories. The evaluated dataset represents an approximately fourfold increase in sample size compared with the prior national study.
Conclusion
U.S. adult CT radiation doses have changed substantially over the past decade. This acquisition-level, size-normalized methodology enables near-real-time generation of national DRLs and ADs, supporting a scalable and actionable framework for modern CT dose benchmarking.