Problem comparison! peak1 = peak 1 or peak 2 of another measurement?


Dear Mrtrix Team,
I have a question concerning the relationship of estimated orientation 1 and 2 (peak1 and peak2). I would like to compare the peaks of different measurements (various b-values etc.).

I already registered all directions to one template. But when I want to consult areas where both proportion of orientation are almost the same I have the problem that I don’t know how I can compare the directions correctly because how can I be sure that peak 1 of measurement 1 is not equivalent to peak 2 of measurement 2?

So my questions are:

  1. Is there a function which resort my orientations hence I can carefully compare orientations per voxel from different measurements? So that in the end all peak1 are corresponding to peak 1.

Thank you


Hi Max,

This is precisely the issue addressed by the fixelcorrespondence command. While that command requires fixel data, “peaks” images (i.e. images with 3xN volumes, where N is the maximum number of peaks in a voxel, and each triplet of volumes correspond to X, Y and Z components of a peak direction) are essentially fixel data; just stored in a different format.



Thank you for your help,
Sorry for asking again but is there a function which creates fixel data out of my peak files without doing fod2fixel, because I have also peak data from another model which doesn’t create fod’s previously? I tried to do voxel2fixel but for that I need already a fixel input is that correct?
Thank you


Unfortunately no. It would be a relatively trivial command to implement ("peaks2fixel"), but nevertheless would require someone to implement and provide that command.

voxel2fixel simply generates a fixel data file where the value in each fixel corresponds to the value stored in the voxel within that fixel resides. So that won’t serve your purpose.