MAPT and Alzheimer disease: While in vitro studies have shown [18F]AV1451 binds predominately to paired helical filament (PHF) of 3R-tau (Marquie et al. 2015) in AD brains, autoradiography studies in post-mortem CBS brains show low, but specific, [18F]AV1451 binding (Marquie et al. 2015; Sander et al. 2016; Lowe et al. 2016).