Hi FSL group,
I'm conducting an exploratory tractography analysis using probtrackx2 in 40 subjects. I'm interested in the pairwise comparisons between 16 ROIs. The ROIs are in MNI space. I'm using ROI_1 as a single mask and ROI_2 as a waypoint mask and termination mask with 5000 samples and am using anisotropy to constrain tracking. I've clicked seed space is not diffusion and have provided the appropriate transformations for a non-linear analysis.
I noticed that for the first 5 subjects it took about 2 days to run per subject and the results looked good with lots of tracks. However, for the next 35 subjects, instead of taking about 2 days to run it took 5 minutes per subject. When I looked at the output, the results were not at all similar to the first 5 subjects and there were hardly any tracks.
I've looked at the transformation files and they seem to be good. I also reran 1 of the first 5 subjects again and instead of the results looking like they did when I initially ran it, this subject now looks like the other 35. I know something is wrong but I can't think of what it might be. Does anyone have any suggestions?
Best,
Dana
|