MAPT and Alzheimer disease: The use of these tracers across the clinical spectrum is critical to understanding how AD pathology emerges and spreads, but each tau-PET tracer has known off-target binding leading to patterns of off-target signal (OTS) which makes quantification in some regions more challenging (Baker et al., 2019; Betthauser et al., 2019; Choi et al., 2018; Marquié et al., 2015; Smith et al., 2021).