[Simnibs-discuss] Coil position

Mana Biabani mana.biabanimoghadam at monash.edu
Thu Jan 21 06:19:38 CET 2021


I am using SimNIBS to simulate TMS-induced e-field and had two questions :

1- Is there any method to measure the exact distance between the coil and scalp surface? The 4mm default distance is not appropriate for my experiment; as the participants have EEG cap on and also there is a foam between the coil and the cap. Also, I’d like to account for the differences in the amount of hair, etc.  I was thinking to measure the minimum euclidean distance between the coil centre and the scalp but as far as I understood the coil centre coordinates are actually scalp positions. So, it shouldn’t work.

2- My second question was about coil angle. I am using the angles that Brainsight provides to make the transformation matrix as below :

[ m0n0	-m0n1	m0n2 	coil.center(1)
 m1n0	-m1n1	m1n2	coil.center(2)
 m2n0	-m2n1	m2n2	coil.center(3)] . 

Could you please confirm if this matrix is correct.  My understanding is that I need to inverse the y axis in Brainsight and it does not need any transformations (like MNI to subject space). Is that correct?

Greatly appreciate your help in advance!

Kind Regards,

Research Fellow

Turner Institute for Brain and Mental Health
Monash University
18 Innovation Walk
Clayton VIC 3800

E: mana.biabanimoghadam at monash.edu <mailto:mana.biabanimoghadam at monash.edu>

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