GRN and frontotemporal dementia: We aim to address the following research questions: can regional MRI volumetry and FDG-PET hypometabolism differentiate (1) FTD patients from healthy controls; (2) sporadic cases of FTD from healthy controls; (3) genetic cases of FTD (MAPT, GRN, and C9orf72 mutations); and (4) underlying neuropathology, specifically discriminating between tau- and TDP-43-based FTD?