Radiation Doses for CAD Diagnostic Tests Vary Widely Worldwide

There is a large degree of variability around the world in the amount of radiation used during diagnostic testing for coronary artery disease, a cross-sectional study shows.

When comparing the same procedures, the median dose of radiation to patients was lowest for nuclear cardiology imaging tests and coronary computed tomography angiography (CCTA) in Western Europe. Doses were highest in Latin America for nuclear cardiology tests and in Africa for CCTA.

“If you look at doses to individual patients, and if you look at Africa, the median dose for a coronary CT angiogram is five times that in Western Europe,” said lead investigator Andrew Einstein, MD, PhD (NewYork-Presbyterian/Columbia University Irving Medical Center, New York, NY). “That being the case, though, there’s a lot of variation within Africa and a lot of variation within Western Europe. So, while there are trends in certain places, within every region of world there is a lot of variability.”

Some of that variability is necessary, he added, noting that more radiation may be needed to obtain good images in heavier patients, but he also said the extent of variability uncovered is “not a good thing.”

To TCTMD, Einstein noted that the incidence of CAD is increasing in the US and around the world, and there is an increasing need for noninvasive imaging to diagnose and treat it. Noninvasive imaging for evaluating symptomatic patients with chronic coronary syndrome has been the “cornerstone” for decades, but some of the testing, such as SPECT, PET, CCTA, and coronary artery calcium (CAC) scoring, exposes patients to ionizing radiation.

“It’s a long-standing interest of mine—we published numerous papers over the years on it—and this, to a certain degree, is a culmination of that because we were able to characterize radiation doses not in one lab or one country, but across the globe,.” he said.

The study, known as the International Atomic Energy Agency (IAEA) Noninvasive Protocols Study (INCAPS) 4, was published this week in JAMA.

Differences by Region

The cross-sectional study included 742 centers in 101 countries, with participating sites required to perform at least one diagnostic procedure involving radiation. Sites provided information about their practices over a 1-week period in 2023. The analysis included data on 19,302 patients, of whom 11,061 underwent nuclear testing and 8,241 underwent CT. Overall, 44% of the tests were done in females.

The median patient radiation effective dose was 1.2 mSv for CAC scoring, 2.0 mSv for PET, 6.5 mSv for SPECT, and 7.4 mSv for CCTA. Doses varied between centers, ranging from 0.8 to 2.4 mSv with CAC scoring to 4.0 to 14.2 mSv for CCTA, for example.

Additionally, the radiation effective dose for the same procedures varied by region. In Western Europe, the median effective dose was 4.8 mSv for nuclear cardiology, 4.6 mSv for CCTA, and 1.0 mSv for CAC scoring. In Latin America, the median effective dose for nuclear cardiology testing was highest, at 7.8 mSv. The median effective radiation doses for CCTA and CAC scoring were highest in Africa, at 25.2 and 2.6 mSv, respectively. 

In all, 81% of centers performing nuclear cardiology and 56% performing CCTA had a median effective dose less than 9 mSv, which is a threshold recommended by the American Society of Nuclear Cardiology. Also, 31% of centers performing nuclear cardiology and 37% performing CCTA achieved a median effective dose of 5 mSv or less.

By region, 89% of centers in Western Europe performing nuclear cardiology had a median effective dose less than 9 mSv compared with 62% and 64% of centers in Africa and North America, respectively. With CCTA, 86% and 91% of centers in North America and Western Europe, respectively, kept radiation levels per case below the recommended 9-mSv threshold compared with 6% of centers in Africa, 35% of centers in the Middle East and South Asia, and 38% in Latin America.

Dose by Income Level

In an analysis by income levels, there was a modest difference in radiation doses across strata: 7.1, 6.4, and 6.1 mSv, respectively, in patients treated in low-/lower-middle-income, upper-middle-income, and high-income countries. There was also no significant difference in median doses at a center level. For example, 84% of centers performing nuclear cardiology in high-income countries kept the effective dose to 9 mSv or less compared with 77% in upper-middle-income countries and 78% in low-lower-middle-income countries.

With CT, however, there was a marked difference in radiation dose by income level. In centers performing CCTA, the median effective dose was 19.8, 12.1, and 5.7 mSv in low-/low-middle-income, upper-middle-income, and high-income countries. In all, 68% of centers in high-income countries, as compared with 19% of those in low-/low-middle-income countries, kept the dose below the 9-mSv threshold. With CAC scoring, the radiation doses were highest in upper-middle-income countries and lowest in high-income countries.

“It underscores the critical need for more training, standardization of protocols, and updated equipment that can reduce radiation worldwide,” said Einstein. “The higher doses occurred particularly for patients in low- and middle-income countries. I think part of that is technology, but part of it is education as well. There’s a need for education worldwide and [awareness] of the importance of optimizing radiation in patients as they undergo cardiac testing.”

Use of new technologies, such as more recent scanner types or, for nuclear cardiology, up-to-date radiopharmaceuticals and equipment, was linked to lower radiation doses in the study. For nuclear cardiology, the median dose was 5.0 mSv with newer and 7.2 mSv with older scanners. With CCTA, the median dose was 6.2 and 14.0 mSv with the new and older scanners, respectively.

While the technology is a factor, Einstein emphasized that operators and centers must develop best practices to minimize radiation with the scanners they have available.