Cardiac PET Perfusion Tracers: Current Status and Future Directions

摘要

Positron emission tomography (PET) myocardial perfusion imaging (MPI) is increasingly used for non-invasive detection and evaluation of coronary artery disease (CAD). However, the widespread use of PET MPI has been limited by shortcomings of the current PET perfusion tracers. Availability of these tracers is limited by need for an on-site (¹⁵O water and ¹³N ammonia) or nearby (¹³N ammonia) cyclotron or commitment to costly generators (⁸²Rb). Due to short half-lives ranging from 76sec for ⁸²Rb, to 2.1min for ¹⁵O water and 10min for ¹³N ammonia, their use in conjunction with treadmill exercise stress testing is either not possible (⁸²Rb and ¹⁵O water) or is not practical (¹³N ammonia). Furthermore, the long positron range of ⁸²Rb makes image resolution suboptimal and its low extraction limits its defect resolution.In recent years, development of an ¹⁸F labeled PET perfusion tracer has gathered considerable interest. The longer half-life of ¹⁸F (108 minutes) would make the tracer available as a unit dose from regional cyclotrons and allow use in conjunction with treadmill exercise testing. Furthermore, the short positron range of ¹⁸F would result in better image resolution. ¹⁸F flurpiridaz is by far the most thoroughly studied in animal models, and is the only F18-based PET MPI radiotracer currently undergoing clinical evaluation. Pre-clinical and clinical experience with ¹⁸F flurpiridaz demonstrated a high myocardial extraction fraction, high image and defect resolution, high myocardial uptake, slow myocardial clearance, and high myocardial-to-background contrast which was stable over time – important properties of an ideal PET MPI radiotracer. Pre-clinical data from other ¹⁸F labeled myocardial perfusion tracers are encouraging.