MAPT and supranuclear palsy, progressive, 1: Although some controversy existed regarding the specificity for 4R tauopathies [6, 9], recent studies have highlighted the potential of [18F]PI-2620 to detect 4R tau pathology in primary tauopathies, showing significantly elevated [18F]PI-2620 uptake in PSP target regions, which correlated with AT8-positive 4R tau aggregates [4, 8].