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| In this tutorial we will compare the performance of the BEM, FEM forward computation in basic model (realistic head model 3 layer) and also within in a spherical head model with an analytical solution. | In this tutorial, we compare the head models computation using the methods available in brainstorm. At this time, the FEM implementation is available for the EEG and the MEG computation. We will integrate and test soon the FEM for sEEG and ECOG. == Spherical head model == In this part we used the spherical head model distributed by the duneuro team ([[https://gitlab.dune-project.org/duneuro/duneuro-tests/-/blob/master/src/test_sphere_tet.msh|sphere]]). The following figure shows on the left the surface model and on right the tetrahedral mesh. {{attachment:DuneuroModelMesh.JPG||height="300",width="600"}} The model has three layers, the brain (inner skull), the outer skull and the scalp. For the source space or dipole position, we will use a realistic cortex distributed with the ICBM default subject of brainstorm. {{attachment:DuneuroModelMeshAnCortex.JPG||height="300",width="600"}} Regarding the electrode's positions, we use the same position defined in this [[https://gitlab.dune-project.org/duneuro/duneuro-tests/-/blob/master/src/test_sphere_electrodes.txt|file]]. The total number of electrodes is 200 regularly distributed on the outer layer. {{attachment:DuneuroModelElectrode.JPG||height="300",width="350"}} the BEM, FEM forward computation in basic model (realistic head model 3 layer) and also within in a spherical head model with an analytical solution. |
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| Compare the performance of the mesh resolution vs the lead field approximation | |
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| v10, v1, v0.1 and v0.01 {{attachment:femMeshModels.JPG||height="400",width="700"}} v0.1 and V0.01 are almost the same .... difference appears on v10 {{attachment:sourceVsMeshResolution.JPG||height="400",width="700"}} in spherical head model same observation on the lf view {{attachment:lfview_v01andv001.JPG||height="400",width="700"}} difference appears on the v1 and worse for v10 |
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| In this example we compute the head model for the ICBM head model using the openmeeg method and then we generate the fem mesh for the same subject, then we compute the the leadfield using the Duneuro method. | In this example we compute the head model for the ICBM head model using the openmeeg method and then we generate the fem mesh for the same subject, then we compute the the leadfield using the Duneuro method v = 0.1 default value. MNorm {{attachment:sourcelocalisation.JPG||height="400",width="700"}} sloreta {{attachment:sourcelocalisationloreta.JPG||height="400",width="700"}} {{attachment:sourcelocalisationloreta2.JPG||height="400",width="700"}} |
In this tutorial, we compare the head models computation using the methods available in brainstorm.
At this time, the FEM implementation is available for the EEG and the MEG computation. We will integrate and test soon the FEM for sEEG and ECOG.
Spherical head model
In this part we used the spherical head model distributed by the duneuro team (sphere). The following figure shows on the left the surface model and on right the tetrahedral mesh. 
The model has three layers, the brain (inner skull), the outer skull and the scalp.
For the source space or dipole position, we will use a realistic cortex distributed with the ICBM default subject of brainstorm.
Regarding the electrode's positions, we use the same position defined in this file. The total number of electrodes is 200 regularly distributed on the outer layer.
the BEM, FEM forward computation in basic model (realistic head model 3 layer) and also within in a spherical head model with an analytical solution.
Describe femVSbem here.
Compare the performance of the mesh resolution vs the lead field approximation
v10, v1, v0.1 and v0.01 
v0.1 and V0.01 are almost the same ....
difference appears on v10
in spherical head model
same observation on the lf view 
difference appears on the v1 and worse for v10
EEG forward within 3 layers head model :
In this example we compute the head model for the ICBM head model using the openmeeg method and then we generate the fem mesh for the same subject, then we compute the the leadfield using the Duneuro method v = 0.1 default value. MNorm 
sloreta 
