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From the Journals

Global Cardiac Imaging Radiation Varies Widely

International study of more than 19,000 patients finds substantial differences in radiation exposure from coronary artery disease imaging across modalities, regions, and income levels.

Conexiant

Forty-four percent of patients undergoing coronary computed tomography angiography received radiation doses above the 9 millisievert guideline target, according to a global cross-sectional study published in JAMA.

The analysis included patients undergoing noninvasive diagnostic testing for coronary artery disease across 742 centers in 101 countries. Median radiation dose varied substantially by imaging modality and geographic region, with coronary computed tomography angiography (CCTA) showing the greatest variability.

Study Design and Population

The International Atomic Energy Agency Noninvasive Cardiology Protocols Study (INCAPS 4) evaluated radiation exposure during routine noninvasive coronary artery disease imaging in 2023. Investigators collected data during a 1-week sampling period between October and December 2023.

Participating sites included hospital and outpatient imaging facilities with a wide range of clinical settings and technology levels. The study included 19,302 adult patients who underwent imaging with nuclear cardiology or cardiac computed tomography modalities.

Among these patients, 8,515 (44%) were female, and the median age was 63 years. Nuclear cardiology studies accounted for 11,061 examinations and cardiac computed tomography (CT) for 8,241.

Investigators estimated radiation exposure using effective dose calculations derived from administered radiopharmaceutical activity for nuclear imaging and scanner-reported dose metrics for CT imaging.

Radiation Exposure by Imaging Modality

Radiation exposure differed across imaging tests. Median effective doses were:

  • 1.2 millisievert (mSv) for coronary artery calcium scoring

  • 2.0 mSv for positron emission tomography

  • 6.5 mSv for single-photon emission CT

  • 7.4 mSv for CCTA

The distribution of doses also varied widely between centers performing the same procedure. For example, center-level median doses ranged from 4.0 to 14.2 mSv for CCTA and from 4.8 to 8.6 mSv for single-photon emission CT.

Guidelines recommend a median effective dose of 9 mSv or less for nuclear cardiology testing. In this study, 81% of centers performing nuclear cardiology met that target compared with 56% of centers performing CCTA.

Overall, 21% of patients undergoing nuclear cardiology testing and 44% of those undergoing CCTA exceeded the 9 mSv dose threshold.

Geographic and Economic Variation

Radiation exposure differed across world regions. Western Europe had the lowest median doses, including 4.8 mSv for nuclear cardiology and 4.6 mSv for CCTA.

The highest median doses were observed in Latin America for nuclear cardiology (7.8 mSv) and in Africa for CCTA (25.2 mSv).

Income level was also associated with radiation exposure. Patient radiation dose was 20% higher in low- and lower-middle–income countries compared with high-income countries for nuclear cardiology, and as much as 96% higher in low- and lower-middle–income countries than in high-income countries for CCTA.

Although differences persisted across regions and income levels, use of newer scanner technology was associated with lower radiation exposure. For example, median dose for CCTA was 6.2 mSv with newer scanners compared with 14.0 mSv with older scanners.

Factors Associated With Higher Dose

In regression modeling, patient effective dose was higher for males than females, as well as in patients with higher weight or BMI, older patients, and patients in low- and lower-middle–income countries.

However, most variation was explained by practice patterns at the center and country levels, which accounted for the majority of dose differences across patients.

Study Limitations

The researchers noted several limitations. Because the total number of eligible imaging centers worldwide is unknown, the representativeness of participating sites cannot be determined. Image quality was not assessed, preventing evaluation of tradeoffs between radiation dose and diagnostic quality.

Additional limitations included reliance on site-reported radiation data and the use of effective dose as a standardized metric, which does not account for individual patient differences such as age or body size.

Despite these limitations, the researchers concluded that the findings highlight opportunities to improve safety and consistency in coronary artery disease imaging worldwide.

“Given increasing rates of coronary artery disease worldwide, these findings of marked variation in radiation dose to patients from diagnostic testing identify a critical need for training, standardized protocols, and updated equipment to reduce radiation worldwide,” the researchers wrote.  

Disclosures: Dr. Einstein reported consulting fees from Artrya, Wolters Kluwer Healthcare-UpToDate, Axcellant, and Canon Medical Systems and research funding from multiple organizations. Dr. Williams reported consulting or speaking relationships with Canon Medical Systems, Siemens Healthineers, Novartis, and FEOPS. Dr. Weir-McCall reported personal fees from Bayer, and Dr. Better reported personal fees from Pfizer. No other disclosures were reported.

Source: JAMA