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


#1

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
Best
Max


#2

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.

Rob


#3

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
Best
Max


#4

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.