Nuclear stress test (NST) practices in the U.S. may be suboptimal, exposing patients to unnecessarily high doses of radiation and possibly increasing cancer risks, according to results of a survey published May 6 in JAMA Internal Medicine.

Approximately 10 million NSTs are performed each year in the U.S. and account for more than 10 percent of the population-wide ionizing radiation burden. Although individual risk from a single NST is low, it may account for thousands of cancer cases on a population basis. A variety of appropriate use criteria for NST and multiple strategies for decreasing radiation exposure have been developed, but based on the new survey results, uptake of these practices has been slow.

The survey, led by Andrew J. Einstein, MD, PhD, FACC, Columbia University Medical Center, NY, included a random sampling of 374 geographically dispersed members of the American Society of Nuclear Cardiology, including physicians, technologists and others. Overall, the study found multiple missed opportunities to reduce radiation exposure. Only 51 percent of respondents reported using dose-reduction strategies, while 15.6 percent reported using dual-isotope testing, which the authors described as "unacceptably high." Stress-only imaging, a strategy that eliminates rest-imaging in patients with normal stress images and decreases radiation exposure by 75 percent, was used by only 7.2 percent of respondents. Also, only 9 percent of respondents could correctly categorize radiation burden from common NST protocols.

"Contemporary U.S. nuclear cardiology practice is characterized by underuse of existing approaches to ensure justification and optimization of ionizing radiation use and by gaps in practitioners' knowledge pertaining to radiation safety," wrote the authors. "Targeted educational programs are needed to better disseminate patient-centered radiation safety practices and effectively incorporate these principles into clinical practice."

"Einstein and colleagues are to be applauded for bravely tackling this difficult problem from within the nuclear cardiology profession," wrote Rita F. Redberg, MD, MSc, FACC, editor of JAMA Internal Medicine. "Because there are more than 10 million nuclear stress tests performed annually, a profession-led campaign to decrease radiation exposure would maintain the benefits of testing but lower the rate of cancers due to these procedures. According to Redberg, "documenting the current practice is the first and an important step in the move to reduce radiation exposure for our patients."

"The report by Einstein et al points out that despite the efforts of ACC and ASNC to encourage radiation reduction methods in cardiac imaging, additional efforts to limit radiation exposure in patients are needed," said Robert Hendel, MD, FACC, director of the Cardiovascular Intensive Care Unit University of Miami Hospital Director of Cardiac Imaging and Outpatient Services. "The optimal method of radiation reduction in some cases is not to perform the test at all, a practice that should be guided by appropriate use criteria. An additional strategy is to eliminate the use of dual isotope imaging entirely, a policy adopted by ASNC. Noting the potential hazard of ionizing radiation, albeit very low for diagnostic imaging, is worthwhile but the well-documented benefits and impact of nuclear cardiology should not be minimized."

Kim Allan Williams, Sr., MD, FACC, vice president of the American College of Cardiology, adds that "the survey also shows that we still have a major growth opportunity for educating our membership on radiation reduction techniques. In terms of tracers, dual isotope SPECT perfusion technique for rest-stress imaging was the standard for a decade and gives a quick yet thorough evaluation, but with a radiation dose that is far too high, more than twice the radiation of a single isotope evaluation with technetum-99m. Patients can be selected for stress only imaging when they are relatively low-risk or when they have had a previous rest-stress exam and no clinical reason to suspect that the resting study would have changed. Lastly there are new software algorithms (e.g., resolution recovery and iterative reconstruction) and new high-speed digital cameras that will allow dramatic reduction in the amount of radioactivity injected. If payment for nuclear imaging is stabilized, laboratories can plan to upgrade their cameras and software to incorporate these advances into their practices."

Keywords: Neoplasms, Radiation, Ionizing, Outpatients, Tomography, Emission-Computed, Single-Photon, Cardiology, Diagnostic Imaging, Radiation Dosage, United States, Exercise Test