MAPT and Alzheimer disease: Both clinical- imaging correlation14-18 and autoradiographic 38,39 evidence, points to AV1451 as a useful measure of the 3R/4R paired helical filament tau deposits that are characteristic of AD and primary age related tauopathy 35.Binding in primary tauopathies (except those that produce 3R/4R fibrillar tau deposits) is less certain.