Gallium-68 Based Positron Emission Tomography (PET) Probes for Myocardial Perfusion Imaging

Abstract

Myocardial perfusion imaging (MPI) is routinely used for clinical evaluation and therapeutic guidance of myocardial ischemia (MI). So far, technetium-99m (99mTc) labeled Single Photon Emission Tomography (SPECT) imaging agents have been the mainstay of MPI, primarily due to the in-house availability of 99mTc radioisotope via generators and the ease of radiolabelling. Over the last decade, Positron Emission Tomography (PET) has emerged as a superior imaging technique with improved imaging quality and image quantification. To utilize the key features of PET in the diagnosis of MI, various Gallium-68 (68Ga) based PET imaging agents were designed and evaluated. Gallium-68 is a generatorbased positron-emitting nuclide and, like 99mTc, can be obtained on an as-needed basis from an in-house 68Ge/68Ga generator system. The ease of radiolabeling and optimal physical half-life of 68Ga (68 min) position it as an ideal PET isotope for MPI. The design of 68Ga-based MPI agents discussed in this review closely followed the physicochemical requirements established for clinically used 99mTc-based MPI agents. We compare and contrast various 68Ga-based complexes used in MPI animal studies and can conclude that select compounds meet the standards set by 99mTc-based MPI agents based on their physicochemical and in vivo properties. Keywords: Cardiac Imaging, Gallium-68, Lipophilic cation, Myocardium perfusion imaging (MPI), Nuclear Imaging, PET Imaging.