Fixelcfestats: nonstationarity

I was trying fixelcfestats with the -nonstationary option and it seemed to have an “unrealistic” effect on the outcome with significant effects in many tracts but with little variation in pvalue. I am doing a group comparison (one sample ttest based on difference images calculated with fixelcalc; the data were preprocessed and analyzed according to the new documentation) and I know that there are global differences in FA - if that’s a clue - and I did the intensity normalization with a CSF mask. I would just like a bit more information on how the nonstationarity is calculated so that I can understand what is going on and if the results are correct.

Hi Örjan,
As documented in the citations section of the help, the method implemented is:

I added this as an option since it was fairly trivial to implement. However, unfortunately I have not had time to test it thoroughly. In my little experience, it reduced the spatial extent of my significant results. However, I guess this was to be expected since the diseases involved fairly large tracts.

Ideally it would be nice to test it with some simulated pathology. As mentioned in the CFE discussion, it would also be nice to explore if there is any orientational sensitivity issues (like TBSS), and if there is, determine if non-stationarity correction fixes this. Unfortunately I can’t see anyone in our lab getting time to look at this any time soon.

I should have seen that; I’ve always stopped scrolling at standard options :slight_smile: My bad.
Sorry to waste your time.