Hi all!
First of all, happy holidays!
Next, I have a question regarding the different types of surfaces that can be obtained with an MRI: BEM, FEM, and the other choices for MRI segmentation (CAT, BrainSuite...).
I (barely) understand the differences between BEM surfaces and FEM meshes, but.. what is the difference between these two, and the other options?. All of these surfaces could be use in the same scenarios?
This question raised because FEM meshes have a different icon. Do this way of generating "surfaces" has different limitations (regarding its usage in Brainstorm)?. Furthermore, The last 4 options in "MRI Segmentation" are sepparated, so this also makes me to wonder the differences between them and BEM/FEM.
PS: I understand that FEM do not generate surfaces but areas. Nonetheless, for simplicity I use the word "surfaces" for areas too.
Thank you in advance!!
BEM and FEM are different approaches to the computation of the forward model.
https://neuroimage.usc.edu/brainstorm/Tutorials/HeadModel#Forward_model
BEM: Boundary Element Methods represent the head as a set of concentric layers of tissues, each of them having homogeneous conductivity properties (e.g. same value of conductivity along all the directions at each point of the skull). The boundaries between these homogeneous tissues are represented with triangular surfaces, which can be computed with two different algorithms (Brainstorm or FieldTrip approaches).
https://neuroimage.usc.edu/brainstorm/Tutorials/TutBem
FEM: Finite Element Methods represent the head as a large number of volume elements (tetrahedrons), each element having its own properties (tissue category and conductivity along each direction). The FEM mesh are 3D tetrahedral meshes, representing the entire head volume.
https://neuroimage.usc.edu/brainstorm/Tutorials/Duneuro