It is hard to say. The 0.25mm may be throwing it off. You can try adding -r
0.25. This will increase the force that repels the pial surface from the white
by a factor of 10. That might be enough. But there are a lot of places where
mris_make_surfaces assumes that the voxels are 1mm. Sometimes people will
change the voxel size in the header to 1mm (so no change to the pixel data,
just a change to the header) and then run that.
On 12/12/2019 7:07 AM, Ardesch, D.J. wrote:
External Email - Use Caution
Dear FreeSurfers,
I’m trying to create surface reconstructions for some small monkey scans (about
half the size of a rhesus macaque). The white surfaces look fine, but I can’t
seem to get the pial surfaces to extend properly to the edge of the gray
matter. Is there a way to ‘force’ the mris_make_surfaces command to place the
pial surface along a certain voxel intensity or intensity gradient?
As I understand it, mris_make_surfaces takes the ?h.orig surface and extends it
into the gray matter until it finds the gray matter/csf boundary. I’ve
therefore tried to edit the brain.finalsurfs.mgz and brainmask.mgz volumes such
that all white matter voxels have an intensity of 110 and all other brain
voxels have an intensity of 80, and added some smoothing to create an intensity
gradient, but this did not make a difference. The gray matter surface is still
placed about 1/5th of the way between the gray/white boundary and the gray/csf
boundary. Adding a T2 scan did not help either.
My setup is the following:
* FreeSurfer v6.0.0
* MacOS 10.14.6
* Running FreeSurfer with the -hires flag (voxel size is 0.25 mm isotropic)
With some manual editing I’ve been able to complete all pipeline steps until
the surface reconstruction, except the topology fixing because it created large
inaccuracies in the occipital lobe (including the topology fixing step did not
solve the problem either).
Any help would be greatly appreciated!
With kind regards,
Dirk Jan
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