MAPT and Alzheimer disease: The second generation of tau PET radiotracers, including (18F)JNJ64349311 [144], (18F)APN-1607 ((18F)PM-PBB3) [145], (18F)MK-6240 [146,147,148], (18F)GTPI [149], (18F)PI-2620 [150] and (18F)RO-948 [151,152,153], offer promising in vivo tools to aid the differential diagnosis between AD and non-AD tau pathology and aid the development of novel pharmacotherapies.