First off thanks for providing the fixel-based analysis framework & documentation, I was able to implement this successfully for a cross-sectional study. Soon I will be attempting to use this framework using longitudinal data, and was wondering if this is currently possible using the existing statistical framework?
My question is more around implementing fixelcfestats for the statistical comparisons. For example, in FSL you can set up your GLM to handle repeated measures by either setting up a paired t-test to test a group difference (which I guess might be possible in CFE), but for a group-difference over time the 4D input file is subtracted over time (e.g. <all_FA_time2 - all_FA_time1>) to test a group difference over time. Given the input for fixelcfestats are individual fixel images, is it possible to generate this ‘subtracted’ fixel? I imagine this might get tricky when dealing with different fibre directions over time…
I think maybe the other option would be to generate whole-brain AFD maps and subtract them over time for a voxel-wise analysis, but I guess the voxel-averaged measure wouldn’t be specific to individual fibre populations. However, if this is the only way to do it at this stage - would it be feasible?
Thanks in advance, looking forward to hearing your suggestions!