Recent efforts to reduce radiation exposure for single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) appear to be successful, according to research presented May 7 at the International Conference on Nuclear Cardiology and Cardiac CT in Vienna, Austria, and simultaneously published in JACC: Cardiovascular Imaging.

Randall C. Thompson, MD, FACC, and colleagues examined data from SPECT MPI studies performed at the Saint Luke's Mid America Heart Institute nuclear cardiology laboratories from January 2009 to September 2016 (n = 18,162). In 2009, all studies were on large field of view Anger cameras. By early 2011, Tl-201 protocols were completely eliminated. New camera models equipped with advanced post processing software replaced older generation large field of view cameras between spring 2010 and fall 2012. Over that time, protocols designed to minimize radiotracer were employed and low-dose stress-first became a default protocol for most patients.

Results showed that after the elimination of Tl-201 and before the widespread usage of new camera technologies, mean effective dose decreased from 17.9 in 2009 to a mean of 12.1 mSv. Since the fall of 2012, the mean effective dose of the studies conducted on small FOV cameras with APPS was 5.6 mSv, and in the studies performed on CZT cameras, mean effective dose was 2.8 mSv. Over 69 percent of MPI studies were performed using low-dose, stress-only imaging. Mean body mass index (BMI) and mean effective dose were much higher for the patients imaged on large field of view cameras since 2014. Over the course of the study, the overall effective dose decreased 60 percent and the median effective dose decreased 76 percent. From 2014-2016, the mean dose of radiotracer rose slightly, as did mean BMI.

"This study demonstrates the compelling impact of a comprehensive radiation reduction strategy in a large nuclear cardiology laboratory network," the authors write. "The data presented here demonstrate that adoption of widely available hardware and software options, and implementation of stress-first/stress-only protocols are practical in real-world daily practice and can result in very low radiation exposures for SPECT MPI."

Keywords: Body Mass Index, Gamma Cameras, Myocardial Perfusion Imaging, Radiation, Tomography, Emission-Computed, Single-Photon, Tomography, X-Ray Computed

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