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Hi all, I was wondering what has been your experiences with tbss and mean diffusivity (or other non-FA) data. We've successfully used tbss on the FA data in our lab, but still have some trouble with MD. The recommended steps were followed through to tbss_non_FA to get the projected MD skeletons for individual subjects (based on the original FA skeleton, as recommended). Performing t-tests on our various data sets processed with this technique, "randomise" yielded wildly significant group differences (1-alpha > .99 for the majority of voxels) even with our "control vs. control" analyses. One thing that I find unusual is that the projected MD values on the skeleton are sometimes lower than the values before projection, which is counter-intuitive to my understanding of the "perpendicular search" strategy for the projection. Inspecting the projected FA values shows them to always be >= the values before projection. If this matters, my scaling factor for MD at step 1 was 2000 (our values range from about 0 to 5, with no negatives). Any advice/suggestions would be greatly appreciated. I'd also like to thank the FSL/TBSS team for the incredibly useful tools you made available. Win