Event Abstract Back to Event A multipole beamformer for improved functional imaging of spontaneous MEG signals Stephen Robinson1* and Jiri Vrba2 1 Henry Ford Hospital, United States 2 Elekta, Finland A scalar LCMV beamformer using a 1st order current multipole (dipole plus quadrupole) forward solution constraint has been developed and tested. The current multipole expansion provides a compact parametric representation of MEG signals arising from sources having significant extent over a curved cortical surface. Although the dipole model has been useful for localizing simple focal sources, it is not optimal for beamformer imaging of spontaneous MEG signals. Epileptic activity and background brain rhythms arise from sources with extent comparable to the distance to the MEG sensors. For any specified coordinate the beamformer weights are computed by first determining the moment vector that maximizes signal-to-noise ratio (SNR). This is done using a variant of Sekiharaâs method, except that the dipole and quadrupole parts of the moment vector must be normalized independently in order to compute the forward solution for the scalar beamformer. This step accounts for their different physical units. All subsequent calculations of virtual sensor waveforms and functional images are derived from SNR to avoid representing activity in mixed units. We compared the multipole and dipole beamformers using simulated data and acquired MEG signals. The spatial selectivity of the multipole beamformer is nearly identical to that of the dipole beamformer for simulation of a single dipole plus noise. However, the multipole beamformer has been shown to be able to resolve two closely spaced dipole sources under conditions where the dipole beamformer could find only a single spatial peak between the sources. Using acquired MEG data the multipole beamformer is shown to localize activity closely to the cortical mantle whereas the dipole beamformer localized the same activity deeper â sometimes within the white matter. In each case, the multipole beamformer yielded higher SNR as a consequence of the improvement in modeling. This research was supported by NIH/NINDS Grant R01 NS30914. Conference: Biomag 2010 - 17th International Conference on Biomagnetism , Dubrovnik, Croatia, 28 Mar - 1 Apr, 2010. Presentation Type: Poster Presentation Topic: MEG Modeling Citation: Robinson S and Vrba J (2010). A multipole beamformer for improved functional imaging of spontaneous MEG signals. Front. Neurosci. Conference Abstract: Biomag 2010 - 17th International Conference on Biomagnetism . doi: 10.3389/conf.fnins.2010.06.00041 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: 19 Mar 2010; Published Online: 19 Mar 2010. * Correspondence: Stephen Robinson, Henry Ford Hospital, Detroit, United States, robinson@neurnis.neuro.hfh.edu 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 Stephen Robinson Jiri Vrba Google Stephen Robinson Jiri Vrba Google Scholar Stephen Robinson Jiri Vrba PubMed Stephen Robinson Jiri Vrba 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.