MAPT and Alzheimer disease: Alzheimer disease (AD) is believed to be caused by the accumulation of amyloid-β (Aβ) in the brain1,2,3 followed by a gradual spread of tau pathology across the brain as the clinical symptoms emerge.4,5,6 Aβ positron emission tomography (PET) for determining the presence of Aβ pathological changes in the brain has been available for more than a decade and there are now several tracers available for clinical use (eg, [18F]florbetapir, [18F]flutemetamol, and [18F]florbetaben).