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Brain Topography

, Volume 29, Issue 4, pp 572–589 | Cite as

The Role of Skull Modeling in EEG Source Imaging for Patients with Refractory Temporal Lobe Epilepsy

  • Victoria Montes-Restrepo
  • Evelien Carrette
  • Gregor Strobbe
  • Stefanie Gadeyne
  • Stefaan Vandenberghe
  • Paul Boon
  • Kristl Vonck
  • Pieter van Mierlo
Original Paper

Abstract

We investigated the influence of different skull modeling approaches on EEG source imaging (ESI), using data of six patients with refractory temporal lobe epilepsy who later underwent successful epilepsy surgery. Four realistic head models with different skull compartments, based on finite difference methods, were constructed for each patient: (i) Three models had skulls with compact and spongy bone compartments as well as air-filled cavities, segmented from either computed tomography (CT), magnetic resonance imaging (MRI) or a CT-template and (ii) one model included a MRI-based skull with a single compact bone compartment. In all patients we performed ESI of single and averaged spikes marked in the clinical 27-channel EEG by the epileptologist. To analyze at which time point the dipole estimations were closer to the resected zone, ESI was performed at two time instants: the half-rising phase and peak of the spike. The estimated sources for each model were validated against the resected area, as indicated by the postoperative MRI. Our results showed that single spike analysis was highly influenced by the signal-to-noise ratio (SNR), yielding estimations with smaller distances to the resected volume at the peak of the spike. Although averaging reduced the SNR effects, it did not always result in dipole estimations lying closer to the resection. The proposed skull modeling approaches did not lead to significant differences in the localization of the irritative zone from clinical EEG data with low spatial sampling density. Furthermore, we showed that a simple skull model (MRI-based) resulted in similar accuracy in dipole estimation compared to more complex head models (based on CT- or CT-template). Therefore, all the considered head models can be used in the presurgical evaluation of patients with temporal lobe epilepsy to localize the irritative zone from low-density clinical EEG recordings.

Keywords

EEG source imaging Skull modeling Refractory epilepsy Forward problem Inverse problem 

Notes

Acknowledgments

This work was carried out using the STEVIN Supercomputer Infrastructure at Ghent University, funded by Ghent University, the Flemish Supercomputer Center (VSC), the Hercules Foundation and the Flemish Government – department EWI

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Copyright information

© Springer Science+Business Media New York 2016

Authors and Affiliations

  • Victoria Montes-Restrepo
    • 1
  • Evelien Carrette
    • 2
  • Gregor Strobbe
    • 1
  • Stefanie Gadeyne
    • 2
  • Stefaan Vandenberghe
    • 1
  • Paul Boon
    • 2
  • Kristl Vonck
    • 2
  • Pieter van Mierlo
    • 1
  1. 1.Medical Image and Signal Processing (MEDISIP)Ghent University–iMinds Medical IT DepartmentGhentBelgium
  2. 2.Laboratory for Clinical and Experimental Neurophysiology, Neurobiology and NeuropsychologyGhent University HospitalGhentBelgium

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