Adult CT radiation doses have decreased substantially over the last decade in the United States, according to new research published in RSNA's Radiology. The study addresses a gap identified by the authors: roughly 10 years have passed since data underlying the most recent national radiation dosing benchmarks were collected, raising questions about whether existing guidelines reflect newer scanner technology, reconstruction methods, and protocol changes.
Kalpana M. Kanal, PhD, of the Department of Radiology at the University of Washington, Seattle, and colleagues analyzed adult CT acquisitions performed across U.S. facilities in 2025 to update these reference values. The researchers found that CT diagnostic reference levels declined an average of nearly 22% since 2014.
The research team noted that “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”.
Study Methodology and Findings
The study drew on data from the Imalogix radiology optimization platform, focusing on the 10 most common adult CT exam categories. Dosing data were extracted from structured reports and normalized at the acquisition level, with patient size quantified using various factors. The final sample included approximately 5.2 million CT exams acquired across nearly 600 U.S. healthcare facilities.
In addition to diagnostic reference levels, dose-length product—described as a key measure of patient dosing across an entire CT scan—decreased by 20%. Dose reductions relative to 2014 were greatest for chest exams with contrast (31%) and without contrast (27%). Smaller reductions were recorded for head exams without contrast material (4%).
Possible Contributing Factors
The analysis did not determine the specific causes of these reductions. However, the authors said the findings are consistent with broader changes in CT technology and clinical practice, including the adoption of machine learning-based reconstruction techniques, refinements in scanner tubes, improved detector efficiency, and increased protocol optimization.
Kanal and co-authors said their analysis offers a scalable, near real-time framework for maintaining diagnostic reference levels and achievable doses going forward.
"The scale, consistency, and automation of this framework support population-level benchmarking for quality improvement and protocol optimization," the authors concluded. "The framework is also well positioned for future incorporation of image-quality metrics, enabling benchmarks that jointly characterize dose and diagnostic performance, and is readily extensible to additional CT applications and subpopulations as clinical practice and technology continue to evolve."
The findings offer an updated, large-scale reference point for adult CT radiation dosing in the U.S., reflecting changes in scanner technology and clinical practice over the past decade.
Source: RSNA Radiology
