[FieldTrip] accommodating air pockets in FEM head model

[Carsten Wolters]

Hi Jeff,

Q3:
yes, FEM can model anisotropy and white matter is anisotropic, but skull 
is a three-layered-structure
consisting of spongiosa and compacta, see
http://www.ncbi.nlm.nih.gov/pubmed/20690140

For Q4:
FEM allows geometry-adaptation, see
http://www.ncbi.nlm.nih.gov/pubmed/17694865
As far as I know, modeling using irregular meshes might get difficult to 
implement within an FDM framework.

For Q1 and Q2:
Mainly tissues between sources and electrodes are important to be 
modeled (so white matter anisotropy
is only important for deeper sources) and FSL and freesurfer can do a 
good job on segmentation.
Air-compartments can possibly best be modeled by hand-correction of the 
FSL output.
Please see
http://www.ncbi.nlm.nih.gov/pubmed/24671208
on how we solve forward modeling to be able to combine EEG and MEG.

More infos are available in the two following theses:
http://www.sci.utah.edu/~wolters/PaperWolters/2014/Lanfer_Dissertation_July2-2014.pdf
http://www.sci.utah.edu/~wolters/PaperWolters/2015/Umit_Aydin_Dissertation_2015.pdf


Best regards
      Carsten

Am 02.12.2015 um 03:04 schrieb K Jeffrey Eriksen:
>
> Hi,
>
> I am reading the FieldTrip documentation on creating an FEM model and 
> see that the following tissue types are output from the segmentation 
> process:
>
> Gray
>
> White
>
> Csf
>
> Skull
>
> Scalp
>
> Q1: Since I am using a 256 channel EGI system with electrodes over the 
> lower part of the head and face, I absolutely need to be able to 
> include air voxels as well. Anyone have any knowledge of such a 
> possibility?
>
> Q2: Beyond that I would also like to include other tissue types such 
> as fat, muscle, and eyeball (vitrious). I suppose I could find other 
> segmentation software to simply create a more varied segmentation and 
> insert it in the processing pipeline, but would like to know if that 
> would mess anything up.
>
> Q3: Next, can the FEM handle anisotropic conductivities for white 
> matter and skull?
>
> Q4: has anyone out there actually used the FDM model?
>
> Thanks,
>
> -Jeff Eriksen
>
>
>
> _______________________________________________
> fieldtrip mailing list
> fieldtrip at donders.ru.nl
> http://mailman.science.ru.nl/mailman/listinfo/fieldtrip

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