How to get the fibers running through some specific fixels?

Hi all,
I ran the fixel-based analysis to compare two groups, and have got the statistical differences in some fixels. Now, I want to know which set of fibers run through these fixels. Is there an easy way to do this in MRtrix?

Hi Zonglei,

If you are looking to select only the streamline segments that exist within statistically-significant fixels, this can currently be achieved using the fixel2tsf command - at least to the extent that this can be used for visualisation.

If you want to select those streamlines for which any part of the streamline is attributed to a statistically significant fixel, but output the entire streamline, this is essentially using a “fixel Region of Interest”. This is currently in development.


Hi Rob,
Thanks for your response. I guess the second option is what I want. I want to get the entire streamlines which pass the significant fixel(even just touch only one) and plot the FD along the streamlines.

When the “fixel Region of Interest” option will released? Besides this, if I want to write code to do this, how to implement it step by step?.


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It’s really difficult to estimate a timeline for the fixel ROI capability, since it’s one component of a larger set of changes that’s just one of many development branches I have going at once. I wouldn’t be holding your breath…

If you wanted to code something up to get yourself by, the best place to start would be the code in cmd/fixel2tsf.cpp. You’d need to modify this to select streamlines based on the input fixel data file, and output the selected streamlines to a track file (there’s a class in src/dwi/tractography/file.h for performing the output).

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