Montes Restrepo, Victoria Eugenia

Vandenberghe, Stefaan

English

Ghent University Academic Bibliography

Localizing sources in the brain: How should wemodel the skull?Victoria Eugenia Montes RestrepoElectronics and Information Systems, Ghent UniversitySupervisor(s): Stefaan VandenbergheThe electroencephalogram (EEG) is the primary tool in the diagnosis of epilepsy, a neurolog-ical disease affecting about 1% of the people worldwide. In most cases, epilepsy can be treatedwith anti-epileptic drugs. When patients do not respond to medication, one of the treatments tobe considered is the surgical removal of the epileptogenic focus, i.e., the zone in the brain origi-nating the epileptic events. To detect this focus and to decide whether surgery can be performed,a presurgical evaluation is needed. As part of this evaluation, engineers have developed a mathe-matical technique called EEG source localization (ESL), which aims at localizing the sources inthe brain from the potentials measured on the scalp. In ESL, the scalp potentials for a given sourceare first computed (forward problem) and then the source parameters that best fit those potentialsare estimated (inverse problem). Solving the forward problem requires an accurate model of thehuman head. The skull is a crucial part of this model due to its high resistivity and complex struc-ture, compared to the other tissues in the head. However, the segmentation of the skull geometryremains unresolved due to the poor visualization of bone in magnetic resonance imaging (MRI).Computed tomography (CT) accurately images the skull but is not commonly performed on pa-tients due to the ionizing radiation. In this work, we analyze the influence of using simplifiedmodels for the skull on ESL. For this purpose, MR and CT images of one patient are used. Ahead model with an accurately segmented skull, including spongy and compact bone as well assome air-filled cavities, is incorporated in the analysis as the reference model. Conductivity andgeometrical simplifications are performed on the skull, generating different models. Based on thesource estimation errors found for these models, we can determine guidelines for skull modelingin the generation of subject-specific head models in a clinical setup of epilepsy.

Localizing sources in the brain: how should we model the skull?

https://biblio.ugent.be/publication/3239185/file/3239209.pdf

Localizing sources in the brain: how should we model the skull?

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Ghent University Academic Bibliography