| | JULY 202319UTLOOKHealthcare Tech Myocardial perfusion imaging (MPI) refers to the use of radiotracers to image regional myocardial perfusion from coronary artery blood flow to the heart muscle. When effectively used, MPI can provide the clinician with a noninvasive technique that yields not only significant diagnostic information, but powerful prognostic data regarding the functional significance of anatomic coronary artery disease. With this data in hand, MPI can help guide the clinician in therapeutic decision-making by risk stratifying patients with respect to future possibility of adverse outcomes.The development of MPI has been a road paved by many twists and turns over the years. It has been a dynamic process involving the development of advances in perfusion radio pharmaceuticals, pharmacologic stress agents, hardware technology, and imaging and processing software. It was not very long ago when the application of physiologic functional imaging added to exercise stress in order to increase the sensitivity of coronary artery disease detection was considered an innovation. From early planar imaging of thallium-201 with rectolinear gamma cameras to now fully digital hybrid SPECT and PET systems with CT, Nuclear Cardiology has come a long way from its original roots.SPECTThe introduction of single photon emission computed tomography (SPECT) capacity in gamma cameras significantly improved the sensitivity and diagnostic accuracy of the technique over early generation rectolinear planar scanners, allowing for better assessment of ischemic burden and/or infarct size in the left ventricle. The development of several technetium-99m based tracers, most notably FDA approval of Tc-99m sestamibi and Tc-99m tetrofosmin, further improved image quality over thallium-201 while reducing total radiation exposure secondary to better inherent imaging characteristics secondary to higher photon energy and significantly lower radioisotope half-lives. A subsequent advancement was the addition of ECG-gating to image acquisition which allowed assessment of left ventricular functional information to further improve interpretation including evaluation of left ventricular size, wall motion, and ejection fraction. Additionally, functional information could aid in the interpretation of perfusion findings improving differentiation of true perfusion abnormalities from artifactual findings related to attenuation and technical factors.PETPositron emission tomography (PET) has arose as another tomographic imaging technique similar to SPECT, but with important unique imaging advantages related to the hardware design and radiation characteristics of positron emitting isotopes, including intrinsically higher image resolution and the capacity for dynamic image and quantitative information acquisition. Pioneering work demonstrating the advantages of myocardial perfusion imaging capabilities of PET did not result in immediate adoption of the technology, primarily due to the limited availability of equipment and PET radio pharmaceuticals. With the greater availability of hardware and PET radiopharmaceutical, this has now changed and PET has gained utilization in the diagnostic imaging mainstream. For cardiology applications, PET offers improved image resolution when compared with SPECT, enhancing detection of abnormalities in regional myocardial perfusion and The Evolution of Myocardial Perfusion Imaging By Patrick Wojtylak, BS HCL CNMT, Supervisor, Nuclear Medicine Department and Arash Kardan, MD, Director of Regional Hospitals Nuclear Medicine, University Hospitals Arash KardanCXO INSIGHTS
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