Copper-62-labeled pyruvaldehyde bis(N4-methylthiosemicarbazonato)copper(II): synthesis and evaluation as a positron emission tomography tracer for cerebral and myocardial perfusion

Abstract

Generator produced positron-emitting radionuclides could potentially expand the application of positron emission tomography (PET) to centers that do not have access to a local cyclotron. The zinc-62/copper-62 radionuclide generator system could serve as a source of positron-emitting copper-62 (62Cu) (t1/2 = 9.74 min) for physiologic imaging. Accordingly, we have prepared zinc-62/copper-62 generators capable of high output (greater than 300 mCi) and used the no-carrier-added eluate in a rapid high yield synthesis of [62Cu] Cu(PTSM) that provides the radiopharmaceutical in a form suitable for intravenous injection (where Cu(PTSM) = pyruvaldehyde bis(N4-methylthiosemicarbazonato) copper(II]. We then demonstrated in pilot studies that [62Cu]Cu(PTSM) provides high quality brain and heart images with PET, accurately delineating cerebral and myocardial perfusion in both experimental animals and in humans (corroborating results of previous experimental studies utilizing longer-lived copper isotopes). The results of this work demonstrate that 62Cu can be conveniently obtained from high-level generators and, when used to label Cu(PTSM), provides a generator-produced radiopharmaceutical capable of providing estimates of cerebral and myocardial perfusion independent of cyclotron-produced radionuclides.