Hello all,
I have a set of tractography points that were externally calculated in the patient's DTI-space. My goal is to map the tracts into MNI space, and I have endeavored to do this by deformation-mapping the individual points. I am having a problem with the results, as there are strange, wavy voids appearing in the resultant mapping.
I normalized the patient's diffusion-space ("s"-prefix) image to MNI space ("w"-prefix), generating a '*_sn.mat' file. I generated the 5-D inverse transform volume from the resultant Tr, and have been calculating the location of each s-point in w-space as follows:
for l=1:size(sVoxPath,1)
C=[sVoxPath(l,1) sVoxPath(l,2) sVoxPath(l,3)]; %C(x,y,z) is the diffusion coordinate in voxels
dC=squeeze(iy(C(1),C(2),C(3),1,:)); %iy is the inverse-deformation
N1=M1*[dC;1]; %M(i,:) are the rows of the inverse of the MNI-vox-to-coord transform
N2=M2*[dC;1];
N3=M3*[dC;1];
wVoxPath(l,:)=[N1 N2 N3]; %Resulting N1, N2, N3 should be the C-coord in MNI voxels
end
My result appears to be in the right space, but with these wavy artifacts that are obviously wrong (see attached image). Is there some step I'm missing? Please let me know if you would like the details of how I calculated the deformation map.
Much thanks,
Eve LoCastro
Research Programmer - IDEAL Lab
Radiology Department
Weill Cornell Medical College
515 E. 71st St S118
Tel: 212-746-1289
Fax: 212-746-4189
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