Hello everybody, I have a doubt with the coordinate system of the brainstorm, i’ve read in the tutorial that when we load the surfaces sensors and other points they are all converted into the CTF system, but i can’t really undestand the whole thing, for example i recently have the opportunity to work with MRI images with fiducials markers to mark the positions of the nasion, INION, LPA, RPA and Cz or middle point of the head so if I import the MRI and I mark those points later on when I tried to use the templates for the standar channel positions they are going to be referenced to them?
Because I wanted to know for sure if those points NAS LPA LRA are the ones who define the coordinate system and also the positions of the channels that I import?
Another question is if there is any way to use fiducial markers for each of the channel positions and then translate those markers to the channel positions in the brainstorm? (because we have plenty of fiducial marker for example for a configuration 10-20 of at least 26 channels)
I ve attached two pictures of the fiducial marker in the mri images. I know that the brainvisa is not your program but since you recommended in your tutorial maybe you know the answer, I had made several 3D brain models with brainvisa but with this fiducial markers the program doesn’t allow me to construct the brain model. Could be a problem related to those fiducial markers?
Note that you markers do not indicate the actual NAS/LPA/RPA. However, I don’t think it can be a problem anywhere.
In BrainVISA: you don’t need those points, you need to set IC/PC/IH/Left hemisphere.
I’ve asked that because I don’t have the Polhemus interface I’m working with signals that a friend hospital is giving me and our only option to have the localization of those points is using fiducials markers.
My brainvisa question is because when I try to obtain the segmented brain model the program always crash tell me that there is no enough memory for allocation and doesn’t happen to me when I’m working with MRI images that don’t have fiducials marker. Maybe there is a problem in the segmentation pipeline when it encounters those markers.
Do you think that it could be possible?
Your data: If you are sure that the points used for the electrodes digitization are the ones you placed in the MRI, it’s what matters.
Check the positions you get in the end (right-click on channel file > MRI registrations > Check).
You can adjust the position of the electrodes and project them on the scalp surface: right-click >MRI Registration > Edit… Read the tooltips of the buttons for help.
BrainVISA: I can’t help you with that, please post your question on their forum.