New research demonstrates significant decreases in radiation dosing for computed tomography (CT) scans performed in 2025.
For the retrospective observation study, recently published in Radiology, researchers reviewed data from 2,802,416 adults who had a total of 5,234,285 CT exams in 2025, and compared CT radiation dosing statistics to a similar study performed in 2014.1,2
In comparison to the previous 2014 benchmarks for CT radiation dosing, the study authors found that national volume CT dose index (CTDIvol) achievable doses (ADs) decreased by 9.3 percent overall across 10 common adult CT examination categories. The researchers also pointed out a 21.8 percent decrease in diagnostic reference levels (DRLs) for CT exams between 2014 and 2025.
“Using a modernized, acquisition-level, size-normalized framework, substantial reductions in U.S. adult CT radiation dose were demonstrated over the past decade,” noted lead study author Kalpana M. Kanal, PhD, who is affiliated with the Department of Radiology at the University of Washington School of Medicine in Seattle, and colleagues.
Specifically, the study authors noted the highest reduction in CTDIVol (mGy) DRL with contrast-enhanced chest CT exams (31.2 percent decrease) and the lowest reduction with non-contrast brain CT scans (3.5 percent decline). Other declines in CTDIVol (mGy) DRL included a 15 percent reduction for contrast-enhanced neck CTs, a 25 percent reduction for non-contrast cervical spine CTs and a 26.7 percent decrease for non-contrast chest CTs, according to the study.
While noting that the study design prevents any definitive assertions about causality, the researchers suggested that hardware advances, improved CT protocols and AI may be key contributing factors with the significant declines in CT radiation dosing.
“The magnitude and consistency of these reductions across examination categories suggest that such advances have translated into measurable, population-level dose reductions in routine clinical imaging in the United States,” emphasized Kanal and colleagues.
Three Key Takeaways
• National CT dose benchmarks have shifted substantially lower. Achievable doses dropped 9.3 percent overall and diagnostic reference levels fell 21.8 percent between 2014 and 2025 across the 10 most common adult CT exam types.
• Dose reduction is highly exam-specific and non-contrast brain CT may be a clear outlier. While contrast-enhanced chest CT led with a 31.2 percent DRL decline and other exams (contrast-enhanced neck 15 percent, non-contrast cervical spine 25 percent, non-contrast chest 26.7 percent) also saw double-digit improvements, non-contrast brain CT lagged behind at just 3.5 percent, a fraction of the reduction seen elsewhere. This gap suggests brain CT protocols have seen comparatively little optimization over the past decade and may represent the strongest remaining target for dose-reduction efforts.
• Updated reference levels could meaningfully lower routine practice benchmarks. The accompanying editorial notes the new 75th-percentile CTDIvol data could translate to roughly 20 mGy lower targets for head CT and 14 mGy lower for routine abdominal CT compared to 2004 ACR benchmarks, practical numbers radiology departments may potentially use to update their own dose-monitoring thresholds for CT exams.
In an accompanying editorial, Cynthia H. McCollough, PhD, praised the authors’ efforts to offer examination and size-specific dosing data that may facilitate updated benchmarking utility for common CT scans in adults. Dr. McCollough noted that the newly reported data for 75th percentile DRLs for CTDIvol. may lead to reductions of 20 mGy for head CT scans and 14 mGy for routine abdominal CTs in comparison to previously established benchmarks recommended by the American College of Radiology (ACR) in 2004.
“This is a remarkable achievement for the CT community, particularly for routine scanning of the abdomen,” posited Dr. McCollough, a Brooks-Hollern Professor and professor of medical physics and biomedical engineering at the Mayo Clinic in Rochester, Minn.
(Editor’s note: For related content, see “Study: PCCT Facilitates Superior SNR and CNR in Lung Cancer Imaging with 55 Percent Reduction in Radiation Dosing,” “Study: More than Half of CT Requests in Pediatric Emergency Department are ‘Usually Not Appropriate’” and “Study Shows 45 Percent Increase in Emergency Department Neuroimaging Over the Last Decade.”)
References
- Kanal KM, Frush DP, Gingold E, et al. A decade of change in adult CT radiation doses: 2025 U.S. diagnostic reference levels. Radiology. 2026;320(1). https://doi.org/10.1148/radiol.260322.
2. Kanal KM, Butler PF, Sengupta D, Bhargavan-Chatfield M, Coombs LP, Morin RL. Radiology. 2017;284(1):120-133.
