Figure 1. A. Composite scans used for paired longitudinal registration. Composite images have high T1-like contrast derived by combining GM, WM and CSF segmentation probability maps in native space (see text). Initial (a) and repeat (b) scans were often acquired at different orientations. The average image (c) represents the symmetric transformation of a & b into a common image space. B. Averaged shrinkage rate (d) and expansion rate (e) across all 84 subjects, demonstrating widespread GM loss in cortical and subcortical regions (d), and expansion in ventricular and sulcal CSF (e).