I am trying to map tumour+oedema lesion masks (generated with ITKSnap) to subjects' freesurfer surface (in native space) using mri_vol2surf.

This is an example of the command I am using for a specific subject:

mri_vol2surf --mov CI_01_t+oedema_corrected.nii \

--fwhm 0 \

--regheader CI_01 \

--hemi lh --surf pial \

--projdist-max 0 1 0.1 \

--interp trilinear \

--surfreg sphere.reg \

--icoorder 5 \

--out CI_01_t+oedema_corrected_lh.mgh

However, I get this error message:

IcoOrder = 5, nIcoVtxs = 10242
srcvol = CI_01_t+oedema_corrected.nii
srcreg unspecified
srcregold = 0
srcwarp unspecified
surf = pial
hemi = lh
ProjDist = 0.5
reshape = 0
interp = trilinear
float2int = round
GetProjMax = 1
INFO: float2int code = 0
INFO: this is an unsiged short. I'll try to read it, but
     
it might not work if there are values over 32k
INFO: using NIfTI-1 qform 
INFO: changing type to float
Done loading volume
Computing registration from header.
 
Using /subjects/CI_01/mri/orig.mgz as target reference.
error: mghRead(/subjects/CI_01/mri/orig.mgz, -1): could not open file
klp32e:7.1.1 Britta$

I have tried the same command with a different freesurfer version (6.0.0), which lead to the same problem. The /mri/orig.mgz loads in freeview and looks fine to me. I searched the mailing list but have not found a post with this error being reported.

I am using version: freesurfer-darwin-macOS-7.1.1-20200811-8b40551

on MacOS Mojave version 10.14.6

I would be very grateful for any advice.