[FieldTrip] issue with FieldTrip-SimBio pipeline for EEG FEM forward solution

[Pierre Bastien Megevand]

Dear all,


I think I have found an inconsistency in the way Fieldtrip handles the building of a FEM forward solution. I am following the procedure described in Vorwerk, Oostenveld et al., The FieldTrip-SimBio pipeline for EEG forward solutions. Biomed Eng Online. 2018 (https://biomedical-engineering-online.biomedcentral.com/articles/10.1186/s12938-018-0463-y). This procedure suggests to build the forward solution by calling the following Fieldtrip functions:

ft_read_mri

ft_volumerealign

ft_volumereslice

ft_volumesegment

ft_prepare_mesh

ft_prepare_headmodel

    ft_read_header (to get electrode data)

    ft_electroderealign

ft_prepare_vol_sens

ft_prepare_sourcemodel

ft_prepare_leadfield


My issue is the following: the FieldTrip-SimBio pipeline explicitly calls ft_prepare_vol_sens, which takes very long to execute (over 6 hours in the case of the published paper, which used about 80 electrodes). However, ft_prepare_leadfield later calls (line 165) prepare_headmodel, which itself calls (line 113) ft_prepare_vol_sens again, with the same parameters as far as I can tell (and again taking ages to run).


Is this redundancy intended? If not, can it be circumvented?


Thank you in advance,


Pierre


Pierre Mégevand, MD, PhD
Senior research associate, Dept. of basic neurosciences
Faculty of medicine, University of Geneva, Switzerland
T. +41 76 693 65 22 | pierre.megevand at unige.ch

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https://doi.org/10.1371/journal.pcbi.1002202