Several dihydrotetrabenazine (DTBZ) derivatives have been labeledwith 11C/18F and developed as PET radioligands.Affinity of dihydrotetrabenazine (DTBZ) toward VMAT2 binding is stereospecific,11 and the (+)-enantiomer showed 1000-fold betterbinding affinity (Ki = 0.97 ± 0.48nM) over the (−)-enantiomer (Ki = 2.2 ± 0.3 μM).12,13 Therefore, PET measurementshave been performed mostly with the (+)-enantiomer of DTBZ derivatives.Two VMAT2 radioligands, [11C]-(+)-DTBZ14,15 and [18F]FP-(+)-DTBZ ([18F]AV-133),16−18 have already been used in several studies in patients with PD. Here, SLC18A2 is linked to Parkinson disease.