Study Finds Wide Radiation Dose Gaps in CT Scans

Researchers analyzing 783,634 adult CT exams found a substantial share exceeded radiation thresholds for their exam type.

Updated on Nov. 3, 2026 in Cancer

Clean editorial illustration of a CT scanner gantry centered in a clinical room, rendered in flat navy, cream, and red tones. — Researchers found 30.7% of 783,634 adult CT scans exceeded radiation thresholds for their exam type, with wide variation across facilities. AI Illustration. Upload story photo >

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A study published November 2 in the Journal of the American College of Radiology assessed facility performance on the CMS ExRad CT radiation measure. Of the CT scans analyzed, 30.7% exceeded the radiation threshold for their exam type, while 0.06% fell short on image quality.

Why it matters

Studies have linked CT exams that exceed recommended radiation thresholds to radiation-related lifetime cancer risk. The findings show considerable variation in how facilities perform on a measure that CMS has adopted into three quality reporting programs.

The analysis covered 783,634 adult CT examinations from 254 voluntarily reporting facilities across 16 CT categories, with abdomen and pelvis, chest, and head exams accounting for 71.9% of out-of-range scans. Within facilities, the median gap between best- and worst-performing CT categories was 74 percentage points, and the study does not address whether these gaps reflect differences in patient populations.

The players

Rebecca Smith-Bindman, MD

Rebecca Smith-Bindman is a physician and researcher at the University of California San Francisco who has studied radiation exposure from medical imaging.

University of California San Francisco

The University of California San Francisco is a public research university and academic medical center based in San Francisco, California.

Centers for Medicare & Medicaid Services

The Centers for Medicare & Medicaid Services is the federal agency that administers Medicare and oversees national health insurance quality reporting programs.

The details

Lead researcher Rebecca Smith-Bindman, MD, of the University of California San Francisco led the study, which examined CT scans performed between May 2025 and August 2026. ExRad reporting began voluntarily in January 2025 and evaluates whether a scan used more radiation than necessary for the patient's indication or produced images too noisy to interpret.

January 2025: Voluntary ExRad reporting began.
May 2025 through August 2026: Period covered by the analyzed CT examinations.
November 2, 2026: Study published in the Journal of the American College of Radiology.

Health Landscape

CMS adopted ExRad into three quality reporting programs, linking radiation dose performance to federal quality oversight of CT imaging. The findings suggest that broad adherence to ExRad thresholds could avoid roughly 24,000 of the projected 103,000 radiation-induced cancers attributed to current CT use each year.

Patients receiving CT scans may benefit from facilities that stay within ExRad radiation thresholds, which the study links to fewer radiation-related cancers. The findings highlight that scan doses can vary widely between facilities for the same exam type.

The takeaway

Facilities that consistently exceed radiation thresholds may contribute to avoidable cancer risk, so patients can ask providers how dose is managed for their imaging. Broader adherence to ExRad could meaningfully reduce the estimated radiation-induced cancers linked to CT use.