Dear all,
Thanks for your replies and suggestions.
We are automatically extracting SEEG channel coordinates from the post-implant CT scans (see http://www.biomedcentral.com/1471-2105/16/99 for details.)
After channel segmentation, we apply rigid transformations to bring channel positions in Freesurfer (SurfaceRAS) space. We are importing channel positions as text file using ASCII Name, X ,Y ,Z format. What is confusing now, is that channel positions are correctly aligned to Freesurfer space if visualized in other tools (e.g. Freeview or 3DSlicer). when imported in Braistorm it seems that we are missing a translation.
We noticed that our volume (i.e. channel positions) is defined with origin in its center (X/2;Y/2;Z/2) while Brainstorm’s CTF space has its origin in the midpoint between RPA and LPA line. So what probably is missing is just the origin translation along Z axis on the channel volume.
Freesurfer surfaces are correctly aligned to MRI,how can we apply the same trasformation to channel positions?
g.