The magnitude of elevations in binding potential was similar to those previously observed in MAPT mutation10 and progressive supranuclear palsy, but lower than those observed in Alzheimer’s disease.13 While this study did not directly compare FTD-TDP (in semantic dementia) to FTD-tau cases, the lack of selectivity of [18F]AV-1451 for tauopathies challenges the utility of this ligand for pathological differentiation in vivo. Here, MAPT is linked to semantic dementia.