Positron emission tomography (PET) has contributed significantly to advancing our understanding of heart physiology and pathophysiology for more than 25 years. Despite its clear success in research applications, the restricted availability of this technology, its increased cost and limited data supporting its use and reimbursement have all contributed to the relatively limited clinical acceptance of it. However, the rapid dissemination of PET/computed tomography (CT) systems initially dedicated to oncology imaging, along with increasing evidence of PET’s clinical efficacy in cardiology and changes in reimbursement, are all contributing to help advance its clinical role in cardiovascular medicine. Additionally, the emergence of integrated PET/CT technology as the dominant configuration of clinical PET scanners also holds great promise for cardiac imaging as it provides a potential opportunity to delineate the anatomical extent and physiological severity of coronary atherosclerosis in a single setting. The objective of this review is to provide the reader with an update on the applications and promises of PET and PET/CT in cardiovascular medicine.
Myocardial Perfusion Imaging Agents for PET
Several myocardial perfusion tracers are approved by the US Food and Drug Administration (FDA) and are available for clinical use, including cyclotron-produced radiopharmaceuticals (N-13-ammonia) and generator-produced rubidium-82. Rb-82 is a potassium analogue with a physical half-life of 76 seconds and kinetic properties similar to those of thallium-201.1 Due to the distinct advantage of not requiring an on-site cyclotron, Rb-82 is the most widely used radionuclide for the assessment of myocardial perfusion with PET. Its parent radionuclide is strontium-82, which has a physical half-life of 26 days. Consequently, the Sr-82/Rb-82 generator is replaced every four weeks. N-13 ammonia is a cyclotron product and has a physical half-life of 9.96 minutes. After injection,13Nammonia rapidly disappears from the circulation, permitting the acquisition of images of excellent quality. The main disadvantage of PET is the need of an on-site cyclotron, which adds cost and is logistically demanding. The recent development of a fluorine-18-labelled (~two-hour half-life) myocardial perfusion imaging (MPI) agent with excellent physiological and imaging properties may facilitate the unit-dose distribution model used for fluorodeoxyglucose (FDG), and thus improve the availability of cardiac PET imaging.2,3
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