Hi, Freesurfers,
Last time I asked about how to convert RAS position into correspongding position in Talairach coordinate of a *.label file. My prupose is to extract vertices with a Talairach coordinate y > 26 in the label.
Later I tried with matlab script freesurfer_label2tal.m. First using freesurfer_read_label, freesurfer_read_talxfm to read *.label and talairach.xfm seperately, then the script convert freesurfer label to Talairach coordinates using following command,
  MNIv = TalairachXFM * LABELv;
  MNIv = MNIv(1:3,:)'; % return Nx3 matrix
  TALv = mni2tal(MNIv')'
Finally I extract vertices with a Talairach coordinate y > 26, then kept these vertices from the original label, and write the result into a new label with freesurfer_write_label.
However, when I load the generated label, I found that it didn't included all vertices with Talairach coordinate y > 26.
eg. As attached, the green point is not in the label, but with a Talaich coordinate y=31.21
Why does this happen?
Is there anything wrong in the procedure?
Any help would be appreciated.
Best!
Jin

2010/11/5 Jin Li <liyuanyuan60@gmail.com>
Hi, Freesurfers,
As the *.label file provide the vertex number and R,A,S positions. How could I get the corresponding position in Talairach coordinates for each vertex?
That is, how could I convert the label in a subject's space into that in talairach space, considering the label is generated from a surface, like shown in the attachment?
I tried to use mri_label2label to convert the label into fsaverage space, but when shown in tksurfer, the RAS position was not similar to Talairach position in fsaverage.
Any help would be appreciated.
Best!
Jin