Cited by 103EEG and Brain-Computer InterfacesNumerical methods in inverse problemsDirection-of-Arrival Estimation Techniques

On MEG forward modelling using multipolar expansions

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Jerbi, K, Mosher, J C, Baillet, S, Leahy, R M·2002·Physics in Medicine and Biology

Abstract

Magnetoencephalography (MEG) is a non-invasive functional imaging modality based on the measurement of the external magnetic field produced by neural current sources within the brain. The reconstruction of the underlying sources is a severely ill-posed inverse problem typically tackled using either low-dimensional parametric source models, such as an equivalent current dipole (ECD), or high-dimensional minimum-norm imaging techniques. The inability of the ECD to properly represent non-focal sources and the over-smoothed solutions obtained by minimum-norm methods underline the need for an alternative approach. Multipole expansion methods have the advantages of the parametric approach while at the same time adequately describing sources with significant spatial extent and arbitrary activation patterns. In this paper we first present a comparative review of spherical harmonic and Cartesian multipole expansion methods that can be used in MEG. The equations are given for the general case of arbitrary conductors and realistic sensor configurations and also for the special cases of spherically symmetric conductors and radially oriented sensors. We then report the results of computer simulations used to investigate the ability of a first-order multipole model (dipole and quadrupole) to represent spatially extended sources, which are simulated by 2D and 3D clusters of elemental dipoles. The overall field of a cluster is analysed using singular value decomposition and compared to the unit fields of a multipole, centred in the middle of the cluster, using subspace correlation metrics. Our results demonstrate the superior utility of the multipolar source model over ECD models in providing source representations of extended regions of activity.

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Research works printed but not linked: 4

  1. Ernè S N, Trahms L and Trontelj Z 1988 Current multipoles as sources of biomagnetic fields Biomagnetism '87 ed K Atsumi et al (Tokyo: Denki University Press) pp 302-5
  2. Haberkorn W 1998 Biomagnetic inverse solutions in terms of multipoles Studies in Applied Electromagnetics and Mechanics 13 ed V Kose and J Sievert (Amsterdam: IOS Press) pp 29-32
  3. Mosher J C, Leahy R M, Schattuck D and Baillet S 1999a MEG Source Imaging Using Multipolar Expansions (Lecture Notes in Computer Science) (Berlin: Springer) pp 98-111
  4. Purcell C, Mashiko T, Odaka K and Ueno K 2000 Describing head shape with harmonic expansion IEEE Trans. Biomed. Eng. 38 303-6

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Authors
Jerbi, K., Mosher, J. C., Baillet, S., & Leahy, R. M.
Affiliations
  • University of Southern California (US)
  • Los Alamos National Laboratory (US)
  • Centre National de la Recherche Scientifique (FR)
Venue
Physics in Medicine and Biology
Published
2002-01-31
Volume
47
Issue
4
Pages
523-555
ISSN
  • 0031-9155 (ISSN-L)
  • 1361-6560
OpenAlex
W2008589555
Cited by
103
References
38
Citations by year
2026: 1 · 2024: 1 · 2023: 1 · 2022: 1 · 2021: 1 · 2020: 3 · 2019: 5 · 2018: 2 · 2017: 3 · 2016: 1 · 2015: 3 · 2014: 4 · 2013: 2 · 2012: 10
FWCI
2.34
Type
journal article
Language
en
Open access
Locations
  • Physics in Medicine and Biology (publishedVersion)
  • PubMed (publishedVersion)
Funders
  • U.S. Department of Energy (W-7405, W-7405-ENG-36)
  • National Institute of Mental Health (R01-MH53213, R01MH053213)
  • Los Alamos National Laboratory (W‐7405‐ENG‐36)
Topics
  • Life Sciences › Neuroscience › Cognitive Neuroscience › EEG and Brain-Computer Interfaces
  • Physical Sciences › Mathematics › Mathematical Physics › Numerical methods in inverse problems
  • Physical Sciences › Computer Science › Signal Processing › Direction-of-Arrival Estimation Techniques
Keywords
magnetoencephalography, multipole expansion, spherical harmonics, equivalent current dipole, source localization, singular value decomposition, realistic head model
MeSH terms
Biophysics, Humans, Magnetics, Models, Theoretical, Magnetoencephalography, Models, Statistical, Biophysical Phenomena

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