Wired head mask after importing subject anatomy

Discussions
1

Dear Francois and BST users,

I'd like to ask a question about the head mask. After importing the subject's anatomy (freesurfer folder), I obtained an extremely wired head mask shown as follows:

without_cortex
without_cortex912×958 107 KB
with_cortex
with_cortex887×975 120 KB

I assume the 'rhinoceros horn' on the nose may be due to the small mirror in front of the face during MRI collecting. However, I have no idea about the 'spikes' on the scalp and what may cause it?
Is this head mask ok for further source estimation analysis? It seems that I can do nothing since all things are automatically imported from the freesurfer folder.
Looking forward to your kind reply and thanks in advance.

Best Regards,
CHEN CHENG

2

The head surface is not imported from FreeSurfer, it is reconstructed by Brainstorm. You can try different parameters to reduce the impact of the artifacts in the MRI (electrodes?):
https://neuroimage.usc.edu/brainstorm/Tutorials/LabelFreeSurfer#Handling_errors

Do your best with the head surface reconstruction, and go on with the source estimation, it should not alter the results too much. If you are using a BEM model, the local irregularities might cause some numerical instabilities. Look at the source maps carefully, check for abnormal values, compare with spherical models to make sure you are on the right tracks.

3

Dear Francois,

Sorry for my late reply and thanks so much. I will have a try to eliminate the artifact and will keep posting if any further problem.

Best Regards,
CHEN CHENG

4

Hi Francois & the Brainstorm team,

I was searching for a topic about odd head masks/models and came across this, as my participant's head mask and BEM head model seems odd.

Attached are screenshots first of the head mask and second of the BEM head model, respectively.

headMask_2024-01-04
headMask_2024-01-041744×542 28.3 KB

BEM_2024-01-04
BEM_2024-01-04928×354 20.4 KB

I'm wondering (1) why there seems to be the extra protrusions at the front and back of the head (MRI artifacts, possibly?), and (2) how much these protrusions might influence the results of sEEG source modeling (and electrode locations). Could you please provide any insights for these questions?

Thank you all very much for your help. We all appreciate it.

Adam