Sensitivity of beamformer source analysis to deficiencies in forward modeling

Abstract

Event Abstract Back to Event Sensitivity of beamformer source analysis to deficiencies in forward modeling Olaf Steinstraeter1*, Stephanie Sillekens1, Markus Junghoefer1, Martin Burger2 and Carsten Wolters1 1 University of Muenster, Institute for Biomagnetism and Biosignalanalysis, Germany 2 University of Muenster, Institute for Computational and Applied Mathematics, Germany Beamforming approaches recently developed for the electro- (EEG) and magnetoencephalography (MEG) source analysis are already widely used. Nevertheless, some fundamental methodological aspects are still quite unclear. Here, we present a systematic study on the influence of improper volume conductor modeling on the source reconstruction performance of an EEG-data driven synthetic aperture magnetometry (SAM) beamforming approach. Simulations were based on a detailed realistically-shaped three-layer (skin, skull, brain) finite element (FE) model of a human head derived from multimodal MR images. Different models for the skull conductivity were used to investigate anisotropy effects. A spherical head model was fitted to study the influence of geometrical misspecifications. The SAM reconstructions were based on pseudo-Z values. Localization errors up to 37 mm were found with a spatial distribution depending on the geometric deviations to the exact model: local differences to spherical shape (spherical head model), local skull thickness. The effect of scull anisotropy was dominated by the radial skull component of the conductivity tensor. By using the exact volume conductor model, the distribution of amplitude and width of the SAM peaks reflected the local signal-to-noise ratio of the sources (pseudo-Z values). For inexact models we found large differences depending on the noise level: The influence of the model differences to amplitude and width of the peaks was large for low noise but less important for higher noise levels. We conclude that depending on source position and sensor coverage, deficiencies in volume conductor modeling might lead to localization errors up to several centimeters. The spatial distribution of peak amplitude and width, important for the assessment of the local relevance of beamformer results, strongly depends on the noise level in the case of inaccurate volume conductor models and becomes nearly unpredictable if the signal-to-noise ratio is high. Conference: Biomag 2010 - 17th International Conference on Biomagnetism , Dubrovnik, Croatia, 28 Mar - 1 Apr, 2010. Presentation Type: Poster Presentation Topic: MEG Modeling Citation: Steinstraeter O, Sillekens S, Junghoefer M, Burger M and Wolters C (2010). Sensitivity of beamformer source analysis to deficiencies in forward modeling. Front. Neurosci. Conference Abstract: Biomag 2010 - 17th International Conference on Biomagnetism . doi: 10.3389/conf.fnins.2010.06.00051 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 21 Mar 2010; Published Online: 21 Mar 2010. * Correspondence: Olaf Steinstraeter, University of Muenster, Institute for Biomagnetism and Biosignalanalysis, Muenster, Germany, Olaf.Steinstraeter@uni-muenster.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Olaf Steinstraeter Stephanie Sillekens Markus Junghoefer Martin Burger Carsten Wolters Google Olaf Steinstraeter Stephanie Sillekens Markus Junghoefer Martin Burger Carsten Wolters Google Scholar Olaf Steinstraeter Stephanie Sillekens Markus Junghoefer Martin Burger Carsten Wolters PubMed Olaf Steinstraeter Stephanie Sillekens Markus Junghoefer Martin Burger Carsten Wolters Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.