Magnetoencephalography signals are influenced by skull defects.


Author: Lau S1, Flemming L2, Haueisen J3.

Affiliation: 1Institute of Biomedical Engineering and Informatics, Ilmenau University of Technology, P.O. Box 100565, D-98684 Ilmenau, Germany; Biomagnetic Center, Department of Neurology, Jena University Hospital, Erlanger Allee 101, D-07747 Jena, Germany; NeuroEngineering Laboratory, Department of Electrical & Electronic Engineering, The University of Melbourne, Parkville 3010, Australia; Department of Medicine - St. Vincent's Hospital, The University of Melbourne, Fitzroy 3057, Australia. Electronic address: stephan.lau@tu-ilmenau.de. 2Biomagnetic Center, Department of Neurology, Jena University Hospital, Erlanger Allee 101, D-07747 Jena, Germany; Department of Traumatology and Orthopedics, Robert-Koch-Hospital, Jenaer Straße 66, D-99510 Apolda, Germany. 3Institute of Biomedical Engineering and Informatics, Ilmenau University of Technology, P.O. Box 100565, D-98684 Ilmenau, Germany; Biomagnetic Center, Department of Neurology, Jena University Hospital, Erlanger Allee 101, D-07747 Jena, Germany.
Conference/Journal: Clin Neurophysiol.
Date published: 2013 Dec 29
Other:
  Pages: S1388-2457(13)01356-4   ,  Special Notes: doi: 10.1016/j.clinph.2013.12.099   ,  Word Count: 215  
    

OBJECTIVE:

Magnetoencephalography (MEG) signals had previously been hypothesized to have negligible sensitivity to skull defects. The objective is to experimentally investigate the influence of conducting skull defects on MEG and EEG signals.

METHODS:

A miniaturized electric dipole was implanted in vivo into rabbit brains. Simultaneous recording using 64-channel EEG and 16-channel MEG was conducted, first above the intact skull and then above a skull defect. Skull defects were filled with agar gels, which had been formulated to have tissue-like homogeneous conductivities. The dipole was moved beneath the skull defects, and measurements were taken at regularly spaced points.

RESULTS:

The EEG signal amplitude increased 2-10 times, whereas the MEG signal amplitude reduced by as much as 20%. The EEG signal amplitude deviated more when the source was under the edge of the defect, whereas the MEG signal amplitude deviated more when the source was central under the defect. The change in MEG field-map topography (relative difference measure, RDM∗=0.15) was geometrically related to the skull defect edge.

CONCLUSIONS:

MEG and EEG signals can be substantially affected by skull defects.

SIGNIFICANCE:

MEG source modeling requires realistic volume conductor head models that incorporate skull defects.

Copyright © 2013 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

KEYWORDS:

Biomagnetism, Breach rhythm, Electroencephalography, Magnetoencephalography, Skull hole, Volume conduction



PMID: 24418220