Bioimpedance spectroscopy and dielectric properties of biological tissues

Abstract

Event Abstract Back to Event Bioimpedance spectroscopy and dielectric properties of biological tissues Igor Lackovic1* 1 University of Zagreb, Faculty of Electrical Engineering and Computing, Netherlands Aim: For accurate forward and inverse modelling in EEG and MEG head tissues dielectric properties are of utmost importance. The purpose of this presentation is: (i) to give an overview of impedance spectroscopy, a powerful method for characterizing dielectric properties and (ii) to present a survey of dielectric properties of various tissues. Methods: Biompedance spectroscopy, which is measurement of dielectric properties (electric conductivity and permittivity) as a function of frequency, requires special attention and careful calibration of measurement equipment. To interface the instrument (LCR bridge, impedance analyzer, network analyzer) to biological sample, various configurations of electrodes, impedance cells and open-end coaxial probes are used. When measuring dielectric properties at low frequencies (up to a few kHz) electrode polarization is the main problem since electric double layers that form at the electrode-electrolyte interface cause large capacitance which has to be corrected for. Electrochemical processes at electrodes are very complicated and depend on electrode material, state of electrode surface, current density, etc. On the other hand, biological tissue, as a measurement object, is very complex in terms of conduction/polarization mechanisms and is generally inhomogeneous (properties vary with space coordinates), anisotropic (properties are different for different directions of propagations), dispersive (properties depend on the frequency of the field) and nonlinear (properties depend on the intensity of the field). At low frequencies biological tissue is predominantly an electrolytic conductor since there are always free ions to migrate. At the same time, biological tissue, due to its complex structure, exhibits in the presence of electric field characteristics of dielectric materials such as polarization. Besides, tissue electrical properties are temperature dependent. Moreover, pathological processes (e.g. tumours) can alter tissue electrical properties. Additionally, as measurements cannot always be performed in vivo post-mortem tissue changes should also be considered. Results: Based on our experimental studies and literature data we illustrate all the above mentioned tissue characteristics (inhomogenity, anisotropy, dispersions, nonlinearity, post mortem changes etc.) and factors affecting accuracy of conductivity and permittivity measurements. We also present results from literature survey on various head tissue conductivities. Apart from results obtained by bioimpedance spectroscopy, which is the main focus of this presentation, we also cover recent magnetic resonance electrical impedance tomography (MR EIT) studies for imaging head tissues conductivity distribution. Conclusion: Results of this presentation may carry important information for EEG/MEG source imaging since accurate solution of EEG/MEG inverse problem depends on accurate values of head tissues conductivities. Conference: NeuroMath COST Action BM0601: Neurodynamic Insight into Functional Connectivity, Cognition, and Consciousness, Dubrovnik, Croatia, 27 Mar - 28 Mar, 2010. Presentation Type: Oral Presentation Topic: Talks Citation: Lackovic I (2010). Bioimpedance spectroscopy and dielectric properties of biological tissues. Front. Neurosci. Conference Abstract: NeuroMath COST Action BM0601: Neurodynamic Insight into Functional Connectivity, Cognition, and Consciousness. doi: 10.3389/conf.fnins.2010.05.00004 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: 24 Jul 2010; Published Online: 24 Jul 2010. * Correspondence: Igor Lackovic, University of Zagreb, Faculty of Electrical Engineering and Computing, Atlanta, Netherlands, igor.lackovic@fer.hr 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 Igor Lackovic Google Igor Lackovic Google Scholar Igor Lackovic PubMed Igor Lackovic 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.