The longitudinal stability of the full-width half-maximum estimation in human brain images was evaluated by computing the maximum absolute difference of the resolution estimation across all time visits for each individual subject.

The figure shows this maximum difference metric for all subjects, where each color represents a unique site ID characterized by a unique manufacturer and scanner model.

In this figure, the maximum difference of 2.20 mm corresponds to axial full-width half-maximum estimations of 6.78 mm, 7.96 mm, and 5.76 mm for the baseline and two follow-up visits, respectively. Note, however, that the voxel size in the axial direction for those images was 3.27 mm, which means that the maximum longitudinal variability is less than a voxel size.