MAPT and supranuclear palsy, progressive, 1: Recently, it is suggested that 11C-PBB3 and 18F-AV-1451 radioligands may show differential selectivity for the different tau isoforms, with 18F-AV-1451 binding predominantly to AD-type tau deposits, whereas 11C-PBB3 and the THK family of tracers exhibiting a higher affinity for non-AD tau aggregates (i.e., 4R as seen in CBD/PSP) (316, 317).