MAPT and early-onset autosomal dominant Alzheimer disease: In the last decade, beginning with the development of 18F-flortaucipir and more recently with the advent of radioligands such as 18F-PI-2620, tau PET imaging has enabled imaging of tau neurofibrillary tangles in people with Alzheimer’s disease as well as co-morbid tau in people with LBD and other neurodegenerative diseases.