MAPT and Alzheimer disease: In the present study, we investigated the possibility that the discrepancies between the above [18F]-PI-2620 in vivo and the autoradiography observations of a low binding affinity of this tracer for tau inclusions predominantly made of 4-repeat tau in non-AD tauopathies—similar to that of Flortaucipir and MK-6240—could be due to the removal of some weaker specific PI-2620 binding by the ethanol washing steps that are routinely used in autoradiography protocols to remove unbound radiotracer.