MAPT and Alzheimer disease: Although tau-PET has faced some problems, such as difficulty in developing a probe with a high affinity for AD-tau and a low affinity for Aβ1–42 (Valotassiou et al., 2018), multiple nuclides, including 11C-PBB3/18F-PM-PBB (Maruyama et al., 2013; Tagai et al., 2021) and 18F-flortaucipir (Leuzy et al., 2019) are now available.