Lessons for Nuclear Cardiology from the DCRI/ACCF/AHA radiation think tank
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This issue of the Journal contains a summary1 of proceedings of a think tank on patient radiation safety in adult cardiology, held in Tyson’s Corner, Virginia in February 2011. The summit was convened by the Duke Clinical Research Institute together with the American College of Cardiology and American Heart Association, and included participation by numerous professional societies sharing this concern, including ASNC. The think tank included a plenary session with talks on various aspects of the problem of patient radiation safety by luminaries in cardiac imaging as well as by industry and regulatory experts, a friendly debate on the benefits and risks of ionizing radiation for cardiovascular care, and breakout groups which developed goals—and strategies for accomplishing these goals—related to four critical issues: risk estimation, measuring and reporting radiation dose, dose-reduction strategies, and education and communication about radiation.
Stakeholders in the radiological protection of patients
Basic and applied science
Academic medical centers
Postgraduate and continuing medical education
ASNC/Choosing Wisely’s list of five commonly used nuclear cardiology procedures whose necessity should be questioned or discussed
1. Do not perform stress cardiac imaging or coronary angiography in patients without cardiac symptoms, unless high-risk markers are present
2. Do not perform cardiac imaging for patients who are at low risk including younger individuals
3. Do not perform radionuclide imaging as part of routine follow-up in asymptomatic patients
4. Do not perform cardiac imaging as a pre-operative assessment in patients scheduled to undergo low or intermediate risk non-cardiac surgery
5. Use methods to reduce radiation exposure in cardiac imaging, whenever possible, including not performing such tests when limited benefits are likely
Illustrating the importance of such cooperation, this clinically driven think tank identified as a priority the intensification of basic and translational research into mechanisms of low-dose radiation effects. Such mechanisms include the bystander effect, a phenomenon through which irradiated cells can induce mutagenesis in neighboring unirradiated cells,5 the adaptive response, through which previous exposure to a low “priming” dose of radiation may be cytoprotective against a subsequent larger dose,6 and genomic instability, by which radiation exposure induces cellular instability that is transmitted to progeny cells, persistently increasing their rates of genetic changes.7 These phenomena and their convergence may result in cancer risks from low-dose radiation that are lower or higher than would be expected from the linear-no-threshold (LNT) hypothesis,8 and thus their elucidation have potentially important clinical implications. The think tank proceedings communicate the need, as perceived by practicing physicians, for support of research into basic radiobiology. In fact, the primary mechanism for funding such research, the Low Dose Radiation Research Program of the Department of Energy’s Office of Science, has been threatened by recent budget cuts.9 Ultimately the interests of patients would be best served here by cooperation between stakeholders as varied as nuclear cardiologists, geneticists, and legislators.
Appropriately, the think tank proceedings provide recommendations aimed at all stakeholders, not just cardiologists. What are some take-home messages that this document delivers specifically for the practitioner? The breakout group on reporting dose recommended ensuring consistent and complete recording in reports of radiation exposure and parameters required to estimate dose. For nuclear cardiology studies, this means we need to document in our reports the radiopharmaceutical(s) used and their administered activities (mCi). The breakout group on dose reduction strategies emphasized education to create a more uniform understanding and approach to dose minimization techniques. For nuclear cardiologists, ASNC has published several documents addressing dose reduction approaches and strategies,10-12 which are worthy of study and implementation in our practices, and numerous talks at the annual meeting in Baltimore will focus on radiological protection, including an entire session on the theme of “Radiation Safety in Nuclear Cardiology and Cardiac CT.” The breakout group on education and communication identified the need to disseminate best practices, including use of appropriateness guidelines and laboratory accreditation. Such appropriate use criteria exist and are regularly updated for radionuclide imaging13; these also merit careful study and implementation. Three organizations—the Intersocietal Accreditation Commission, the American College of Radiology, and the Joint Commission—offer the opportunity to have our laboratories accredited.
Thus, by taking concrete efforts to improve radiation safety in our own practices, and by working together with a wide range of stakeholders to create a culture of safety, we can move towards the twin goals of keeping radiation doses as low as reasonably achievable (ALARA), and keeping the benefits-to-risks balance of cardiac imaging as high as reasonably achievable (AHARA).1 As pointed out in the think tank proceedings, this is an ongoing process. While the Tyson’s Corner think tank represented neither a beginning nor an end of this journey, it served as an important meeting point to share ideas and set goals with a broad spectrum of experts, and a milestone along the road of progress for radiation protection in cardiovascular medicine.
Conflict of interest
Dr. Einstein was supported in part by National Institute of Health Grant 1R01 HL109711.