Across the 15 tissue ROIs, the CV for the sequential method was 3.0% and for the independent method was 9.4%. This difference was significant with the Wilcoxon test (Z=2.953, p=.0031), favoring the sequential method. As a further test of the robustness of the sequential method, we reversed the temporal order of the intra-subject registration with the SRI24 atlas, so that the reformatting sequence was SRI24 - MRI 2 - MRI 1. The average CVs for this reversed sequence was 4.2% and also was significantly lower than that of the direct method (Z=2.272, p=.0231) but not significantly different from that of the forward sequential method (Z=0.568, p=.5701). The CVs for the ICV was 9.7% for both the direct and sequential methods.
