United States Lags Behind on Best Practices to Reduce Radiation From Nuclear Imaging

The United States has much greater use of myocardial perfusion imaging (MPI) compared with other parts of the world, but at the same time, US nuclear cardiology labs lag behind in adhering to best practices for reducing radiation doses—and, potentially, hundreds of cancer cases annually—according to 2 research letters.

A lack of accountability coupled with financial considerations likely contributes to this subpar performance, experts say.

“When it comes to medical imaging tests, it is time for physicians who order the tests to join together with radiologists and other physicians who perform imaging studies to form a consensus guided by patients’ values about the pressing need to perform imaging tests more wisely,” Rebecca Smith-Bindman, MD, and Andrew Bindman, MD, of the University of California, San Francisco, write in an editorial accompanying the studies, which were published online last week in JAMA Internal Medicine.

“The establishment of meaningful measures of performance in combination with payment reform offers the best hope of improving the value and safety of medical imaging studies,” they say.

The 2 studies “demonstrate that not all MPI tests were created equal from the radioprotection standpoint and you can buy the same diagnostic information at very different radiological costs in different countries, and even in different laboratories of the same country,” Eugenio Picano, MD, of the Institute of Clinical Physiology (Pisa, Italy), told TCTMD in an email.  (Our detailed Q&A with Picano is published here.) “The findings highlight the need to audit doses in cardiac imaging labs, to track cumulative exposures, and to standardize doses for each technique," he said.

Use of Best Practices Varies Widely

An International Atomic Energy Agency (IAEA) expert panel has identified 8 laboratory best practices affecting radiation doses. These involve minimizing use of thallium and technetium Tc 99m, performing stress-only imaging in some patients, using camera-based dose-reduction strategies, and eliminating shine-through artifact.

To examine use of these best practices and differences in radiation dose in US and non-US labs, a team led by Andrew Einstein, MD, PhD, of NewYork-Presbyterian Hospital/Columbia University Medical Center (New York, NY), looked at data from the IAEA Nuclear Cardiology Protocols Study (INCAPS), a cross-sectional registry of patients undergoing MPI in 308 nuclear cardiology laboratories in 65 countries (including 50 US labs in 22 states) during a 1-week period between March 18 and April 22, 2013.

The first study showed that the mean number of best practices used was lower in the United States than in other parts of the world (4.6 vs 5.6; P < .001), with a smaller proportion of labs adhering to at least 6 of the 8 (30.0% vs 49.2%; P = .01).

Although US labs outperformed non-US facilities in avoiding thallium stress imaging in patients younger than 70 years, they lagged behind in 4 of the other 7 practices.

The lower adherence to best practices translated into a median radiation dose that was about 20% higher in US than in non-US labs (11.6 vs 9.7 mSv; P < .001).

The authors note that these findings come on the background of more frequent use of MPI in the United States than in other developed countries. There are 2,500 MPI studies performed for every 100,000 Americans. In comparison, the rates per 100,000 population are 1,200, 364, 315, and 120 in Canada, Australia, Japan, and the United Kingdom, respectively.

“Improvements in adherence to these best practices offer potential opportunities, that do not require any specific technology, to reduce the radiation burden of MPI in the United States through greater attention to patient-centered imaging,” Einstein and colleagues write.

Stress-Only Imaging

The second study focused on the best practice of using a stress-only imaging protocol, in which stress imaging is done first and subsequent rest imaging is only performed if the stress images are abnormal. That practice has been shown to reduce radiation burden without impairing patient safety, but a US survey suggested that stress-only protocols are not commonly performed.

To explore the issue, Einstein’s team again turned to the INCAPS registry. They found that rates of stress-first and stress-only protocols varied widely among regions and were lowest in North America. Stress-first ranged from 7.7% in North America to 89.9% in Africa, and stress-only ranged from 3.1% in North America to 32.4% in Africa.

Among eligible studies, mean effective radiation dose decreased by 63.6% (from 11.0 to 4.0 mSv; P < .001) when a stress-only protocol was used.

Modeling resulted in an estimated reduction of 20.9% in the mean effective radiation dose from MPI if US labs adopted stress-only imaging at the same rate as the top 10% of all INCAPS labs, which “might prevent hundreds of cases of cancer annually,” according to the authors.

Suboptimal US Performance

There are multiple factors holding US labs back from implementing best practices, Einstein told TCTMD in an interview. First, he said, there is a less intensive culture of safety in the United States compared with other parts of the world.

Financial disincentives to performing stress-only MPI also may play a role, he said. Labs receive $137 more when both rest and stress imaging are performed than they do when performing only stress tests. Such economic disincentives may also exist for the other best practices.

And finally, Einstein said, the resistance to using best practices, some of which involve tailoring protocols to individual situations, may come from the existence of a one-size-fits-all culture that does not facilitate optimization of radiation doses for each patient.

Reform Needed

In their editorial, Smith-Bindman and Bindman say the studies “suggest that our problems in the use of imaging studies are not just the increasing rate of unnecessary tests but also the marked variation in how safely the tests are performed.”

The growth in the use of imaging over time and the variation in the amount of radiation delivered may be due to the lack of a system of accountability for overseeing the quality of decision making and penalizing overuse or misuse, they say, as well as the existence of a fee-for-service payment system that “incentivizes volume over value.”

They point out that Congress has created the Medicare Incentive Payment System, “which will soon place Medicare physicians at financial risk for their practice style.” The system allows physicians to choose to have Medicare payment affected by their performance compared with other Medicare physicians or to join accountable care organizations. Quality metrics are still being worked out.

“Medicare could achieve significant cost savings and contribute to a reduction in unnecessary and harmful radiation by making the safe and appropriate use of expensive imaging tests, such as CT scans and MPI, part of its performance measures,” the editorialists argue.

In addition to working on financial incentives, adherence to best practices may be improved by integrating them into systems of accreditation for nuclear cardiology labs and by improving education about how these efforts influence patients’ radiation exposure, Einstein added.

“Our intention was not to be alarmist in terms of scaring people away from having these tests, but [we were] just pointing out that in the United States there are certainly opportunities for us to improve on our practice and lower radiation doses to patients,” he said.

Sources: 
1. Mercuri M, Pascual TNB, Mahmarian JJ, et al. Estimating the reduction in the radiation burden from nuclear cardiology through use of stress-only imaging in the United States and worldwide. JAMA Intern Med. 2015;Epub ahead of print.
2. Mercuri M, Pascual TNB, Mahmarian JJ, et al. Comparison of radiation doses and best-practice use for myocardial perfusion imaging in US and non-US laboratories: findings from the IAEA (International Atomic Energy Agency) Nuclear Cardiology Protocols Study. JAMA Intern Med. 2015;Epub ahead of print.
3. Smith-Bindman R, Bindman AB. Imaging more wisely [editorial]. JAMA Intern Med. 2015;Epub ahead of print.

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