MAPT and supranuclear palsy, progressive, 1: A strength of this study is given by the use of the novel tau-PET tracer [18F]PI-2620 which proved absent of off-target binding to monoamine oxidases [76], high affinity to 3/4R-tau in AD [77] and also high affinity to recombinant 4R tau fibrils and PSP brain homogenate [76].