Hello Dr. Greve,
I used the bbregister tool to register a BOLD EPI volume to the
surface with the --init-fsl option. The result looks good in
tkregister2. Using the resulting .dat file, I am trying to express the
vertex coordinates of the surface in EPI voxel space (EPI volume: 128
x 128 x 36 matrix, limits: -64 to 64, -64 to 64 and -18 to 18).
Given the following 4x4 matrices,
vox2ras_epi : vox2ras transformation matrix from the EPI volume header
bbregMat : transformation matrix from the .dat file created from
bbregister command
Given the vertices of the subject's surface (nVert x 4) : srfVert
I used the following transformation to express the surface in EPI
voxel coordinates:
srf_epiVox = srfVert * inv(bbregMat) * inv(vox2ras_epi)
When I view the results of this transformation in MATLAB, I can see
that the above expression is incorrect. I used imagesc to show one
slice of EPI and scatter to plot of all the vertices in that slice.
Can you please let me know what the mistake is? Am I applying the
transformation in an incorrect coordinate space? Am I missing any
transformations?
Looking forward for your reply. Thank you.
Yours Sincerely,
Praneeth