Recent advances in the understanding of frontotemporal dementia (FTD) and subsequently, the development of novel disease modifying treatments, has stimulated the need for tools to assess treatment efficacy. While perfusion imaging by arterial spin labeling (ASL) is an attractive approach, its sensitivity to detect longitudinal changes in perfusion in dementia patients remains unknown. Longitudinal variability in perfusion was assessed on a voxel-by-voxel basis over a month. Power analysis revealed ASL has the sensitivity to longitudinal changes as low as 7-8%. These results highlight the potential of ASL for detecting longitudinal changes in FTD populations.