MAPT and Alzheimer disease: Among these tracers, PBB3 is reported to bind tovarious types of tau fibrils with comparable binding affinities.In contrast, tau tracer AV-1451 is reported to bind to specific typesof tau fibrils (in particular to AD-associated and CTE) with higherbinding affinity and only show nonspecific or weaker binding towardtau fibrils dominant with 3R isoforms (associated with PiD).