Hallez, Hans

Montes Restrepo, Victoria Eugenia

Staelens, Steven

van Mierlo, Pieter

English

Ghent University Academic Bibliography

Accurate(skull(modeling(from(MRI(for(EEG(source(localization!! V.!Montes*Restrepo,!P.!van!Mierlo,!H.!Hallez,!S.!Staelens!!Keywords:! Realistic! head! modeling,! Finite! Difference! Method! (FDM),! skull!inhomogeneities!!!Abstract(!In!EEG!source!localization,!the!skull!plays!an!important!role!due!to!its!low!conductivity!compared!to!other!tissues!in!the!model!and!due!to!its!inhomogeneity!as!thickness!and!conductivity! varies! throughout! its! structure.! While! MRI! is! the! most! used! imaging!modality! for! the! visualization! of! the! head! structure,! it! does! not! allow! an! exact!distinction! of! the! skull! and! its! tissue! types.! Conversely,! CT! is! the! modality! that! can!accurately! describe! the! geometry! of! the! skull! but! is! not! commonly! performed! on!patients!due!to!ionizing!radiation.!We!investigated!the!effect!of!using!MR*based!models!for!the!skull!as!opposed!to!a!ground!truth!CT*based!skull!model.!A!head!model!with!an!accurately!segmented!skull!from!CT,!including!compact!and!spongy!bones!as!well!as!air!cavities,!was! used! as! reference.! To! analyze! the! influence! of! using!MR*based! skulls,! 4!models! were! constructed! with! skull! geometry! and! air! cavities! segmented! from! MRI!using! SPM! toolbox:!M1! –! isotropic! inhomogeneous,! the! spongy!bone!was!modeled! as!eroded! compact;! M2! –! anisotropic! homogeneous;! M3! –! hybrid,! isotropic!inhomogeneous!in!the!vault!(as!M1)!and!anisotropic!in!the!base!(as!M2);!M4!–!isotropic!homogeneous.!The!forward!problem!was!solved!through!FDM!with!Reciprocity!using!128!electrodes.!The!estimated!dipole!parameters!were!chosen!as! the!ones! that!best! fitted! the!surface!potential.! Large! errors! in! the! temporo*basal! region!were! seen! in! Figs.! 1(a)! and! 1(d)!where! the! difference! in! shape! between! MR! and! CT*based! skulls! is! particularly!noticeable.!In!Fig.!1(b),!the!errors!were!smaller!in!the!basal!region!but!more!distributed!in! the!whole!volume.!The!hybrid!model,!Fig.!1(c),! showed!overall! lower!errors.!When!the!geometry!of!the!skull!cannot!be!accurately!segmented,!the!isotropic!inhomogeneous!model! (M1)! can! better! model! the! cranial! vault! but! anisotropic! conductivity! (M2)! is!appropriate! in! regions! such! as! the! skull! base.! Then,! for! a! patient*specific! MR*based!head!model,!the!skull!will!be!better!modeled!as!in!M3.!!!!!!!!((((((((((((((((((((

Accurate skull modeling from MRI for EEG source localization

https://biblio.ugent.be/publication/3239245/file/3239306.pdf

Accurate skull modeling from MRI for EEG source localization

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Ghent University Academic Bibliography