If the original brik is 161 X 191 X 151, in mm, and the RAS space is 256 X 256 X 256, where do the additional voxles come from? I thought that the original space was stretched to fit 256^3, but from your replay it looks like it is just padded?
thanks, Rutvik
On Wed, 26 May 2004, Bruce Fischl wrote:
Hi Rutvik,
I'm not sure I understand - the nodes live in a mm RAS coordinate so distances between them should be intrinsically in mm.
Bruce
On Wed, 26 May 2004, Rutvik Desai wrote:
Hello,
I have FreeSurfer surface models created from Talairached AFNI (+tlrc) briks. I am interested in computing distances between nodes on these (orig or smoothwm) surfaces in mm units. The +tlrc briks are 161mm (R-L) X 191mm (A-P) X 151mm (I-S). with 1X1X1 mm^3 voxels. talairach.xfm or any such files or transformations were not used. As I understand, FreeSurfer would resample this brik into a 256 X 256 X 256 RAS coordinate space. There are the coordinates you see when you look at say a ?h.smoothwm.asc file. To interpret these coordinates in terms of mm, one could multiply the X coordinate by 161/256, Y by 191/25, and Z by 151/256. The distance between two nodes computed with these modified coordinates should be in mm. Is this correct or am I missing something?
thanks, Rutvik _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer