MAPT and Alzheimer disease: Using [18F]flortaucipir, the most widely studied tau PET tracer to date, significant tracer retention has been observed in the basal ganglia, thalamus, and the choroid plexus, regions not shown to exhibit AD-like tau aggregates.16,17,18 As a result, novel tau PET tracers with reduced off-target binding in these regions have been developed,19 including [18F]PI-2620, [18F]GTP1, [18F]MK6240, and [18F]RO948.