Study: U.S. patients subject to higher radiation during MPI heart test

Americans undergoing myocardial perfusion imaging to diagnose coronary artery disease, a leading killer in the U.S., are receiving higher levels of radiation than their peers around the world, according to a new study.

The study was published in JAMA Internal Medicine this month.

The MPI test, performed on millions of U.S. patients every year, is a non-invasive imaging exam in which heart muscle blood flow is measured and areas with low flow are identified.

According to the study, which looked at 7,911 patients in 308 nuclear cardiology labs across 65 countries, Americans undergoing the screening received a dosage on average that was almost 20% higher than the international average, and less U.S. patients, around 24%, received doses lower than the recommended 9 mSv.

Data from the study also indicated that American MPI patients were on average 2 years older, and a larger proportion, 43.2% versus 40.5%, were women. Study data was collected from 1-week stretches between from March 18 and April 22, 2013

“We observed a 20% higher radiation dose to the typical patient undergoing MPI in a U.S. laboratory compared with a patient in a non-U.S. laboratory. This difference results in part from lower adherence to radiation-dose best practices among U.S. laboratories,” study authors said in the report.

While the study reports that U.S. laboratories outperformed non-U.S. labs in avoiding thallium stress imaging in patients under 70, the labs underperformed compared to their international counterparts in 4 of 7 other recommended practices. Only 7 of a total 50 U.S. labs kept the median dose below the recommended 9 mSv, compared to 84 of 258 non-U.S. labs.

In addition to higher dosages, important practices, such as weight-based dosing and the implementation of stress-only protocols in select patients, were used less frequently in U.S. facilities, the study reported.

Those deficits are coupled with a much higher rate of MPI usage, with the U.S. averaging 2,500 MPI studies per 100,000 individuals, nearly double the rate of testing in Canada, Australia, Japan and the U.K. combined.

Authors of the study said the U.S. could see a reduction in radiation burden during MPI exams through adherence to best practices and greater attention to patient-centered imaging.

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