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Design of electrodes and current limits for low frequency electrical impedance tomography of the brain

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Abstract

For the novel application of recording of resistivity changes related to neuronal depolarization in the brain with electrical impedance tomography, optimal recording is with applied currents below 100 Hz, which might cause neural stimulation of skin or underlying brain. The purpose of this work was to develop a method for application of low frequency currents to the scalp, which delivered the maximum current without significant stimulation of skin or underlying brain. We propose a recessed electrode design which enabled current injection with an acceptable skin sensation to be increased from 100 μA using EEG electrodes, to 1 mA in 16 normal volunteers. The effect of current delivered to the brain was assessed with an anatomically realistic finite element model of the adult head. The modelled peak cerebral current density was 0.3 A/m2, which was 5 to 25-fold less than the threshold for stimulation of the brain estimated from literature review.

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Acknowledgments

The authors would like to acknowledge Ilan Gilad from the Ben-Gurion University of the Negev, Israel, for manufacturing the recessed electrodes and Solange Akselrod2 for her comments during the preparation of this manuscript. This study was funded by the Epilepsy Research Foundation, UK, the Ministry of Science & Technology, Israel and by grant NIH 1R01EB006597-01 from The National Institutes of Health, US.

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  1. Department of Medical Physics and Bioengineering, Malet Place Engineering Building, University College London, Gower Street, London, WC1E 6BT, UK

    O. Gilad, L. Horesh & D. S. Holder

  2. Raymond and Beverly Sackler Faculty of Exact Sciences, School of Physics and Astronomy, Abramson Center for Medical Physics, Tel Aviv University, P.O. Box 39040, Tel Aviv, 69978, Israel

    O. Gilad

  3. Scientific Computing, Mathematics and Computer Science, Emory University, Atlanta, GA, USA

    L. Horesh

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Gilad, O., Horesh, L. & Holder, D.S. Design of electrodes and current limits for low frequency electrical impedance tomography of the brain. Med Bio Eng Comput 45, 621–633 (2007). https://doi.org/10.1007/s11517-007-0209-7

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