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Principles of Magnetoencephalography

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Clinical Applications of Magnetoencephalography

Abstract

Magnetoencephalography (MEG) is a neuroimaging tool which obverts functional brain maps or pathognomonic signs with millisecond order, but some computational technique appears to be a black box. To relax such complex matter for general readers, we introduce the principles of MEG computation briefly. This chapter consists of three steps: first, we introduce the basic concept of MEG; next, we describe forward solution; and finally, we address inverse problem for understanding of MEG source localization concept. MEG detects varying magnetic fluxes derived from enormous amount of intracellular currents within pyramidal layer in folded cortices, and estimation of these source activities is essential to the MEG utilization. Here, we introduce typical three source localization algorithms: equivalent current dipole (ECD), minimum norm estimation, and adaptive beam former. To estimate ECDs from measured sensor signals, repeated seeking operation is undertaken so that errors between measured signals and calculated signals are minimized. Fundamental concept of minimum norm estimation has constraint subject to minimizing total currents of all nodes. Minimum variance estimation, the so-called adaptive beam former, has constraint subject to minimizing the variance of time-series current at one node. We hope that this introduction might help readers to understand the basic theory of MEG source localization.

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Author information

Authors and Affiliations

  1. Department of Neurosurgery, Hiroshima University, 1-2-3 Kasumi, Minami-Ku, Hiroshima, 734-8551, Japan

    Akira Hashizume

  2. Takanobashi Central Hospital, Hiroshima, Japan

    Akira Hashizume

  3. Department of Clinical Neurophysiology, Kyushu University, Fukuoka, Japan

    Naruhito Hironaga

Authors
  1. Akira Hashizume
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  2. Naruhito Hironaga
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Correspondence to Akira Hashizume .

Editor information

Editors and Affiliations

  1. Department of Clinical Neurophysiology, Kyushu University, Higashi-ku, Fukuoka, Japan

    Shozo Tobimatsu

  2. Natl. Inst. for Physiological Scien, Dept. of Integrative Physiology, Okazaki, Aichi, Japan

    Ryusuke Kakigi

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Hashizume, A., Hironaga, N. (2016). Principles of Magnetoencephalography. In: Tobimatsu, S., Kakigi, R. (eds) Clinical Applications of Magnetoencephalography. Springer, Tokyo. https://doi.org/10.1007/978-4-431-55729-6_1

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  • DOI: https://doi.org/10.1007/978-4-431-55729-6_1

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  • Publisher Name: Springer, Tokyo

  • Print ISBN: 978-4-431-55728-9

  • Online ISBN: 978-4-431-55729-6

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