Localized electrical energy concentration method for multi-electrode bioimpedance measurement H. Kwon 1 , H. Wi 2 , B. Karki 2 , E.J. Lee 1 , A. McEwan 3 , E.J. Woo 2 , B. Harrach 4 , J.K. Seo 1 and T.I. Oh 2 1) Department of Computational Science and Engineering, Yonsei University, KOREA 2) Impedance Imaging Research Center and Department of Biomedical Engineering, Kyung Hee University, KOREA 3) The School of Electrical and Information Engineering, The University of Sydney, AUSTRALIA 4) Institut f¨ur Mathematik, University of W¨uurzburg, GERMANY Corresponding Author : H. Kwon,
[email protected] ABSTRACT Impedance spectrum in a biological sample may provide diagnostic information due to the changes of impedance related to physiological and pathological conditions. The tetrapolar electrode system on biomaterials has commonly used for measuring impedance to reduce the influence of electrode polarization effect. However, this method is still affected by negative sensitivity regions (It has low sensitivity ratio of conductivity contrast) and it doesn’t focus on detection in local region underneath the electrodes. The proposed BIS method effectively estimates the conductivity in a local region just underneath the probe. The main idea is to use a focused current pattern that produces a localized electrical energy concentrated in the local region underneath the probe. With these focused current patterns, the corresponding voltages are mainly depending on the conductivity distribution in the local region near the probe. Therefore, we may get some linear relation between the local conductivity and the voltage data induced by the focused current. In this paper, we describe the localized electrical energy concentration method for bioimpedance using multiple miniature electrodes and evaluate the method with experimental results. Also, it can estimate the anisotropic property of an object since bioimpedance of anisotropic object such as a muscle has different characteristics along the measurement direction. There is possible to provide incorrect results caused by anisotropy of testing objects. We have a plan to apply this method to collect spectrum from the biological tissues and apply for an imaging system in order to reconstruct the local region of interest (ROI) only. REFERENCES 1.
Gabriel S, Lau R W and Gabriel C, “The dielectric properties of biological tissues: II. Measurements in the frequency range 10 Hz to 20 GHz”, Phys. Med. Biol., Vol. 41, 1996, pp. 2251-2269.
2.
Blad B and Baldetorp B, “Impedance spectra of tumour tissue in comparison with normal tissue; a possible clinical application for electrical impedance tomography”, Physiol. Meas., Vol. 17, 1996, pp. A105-A115.
3.
Wang L L, Ahad M, McEwan A, Li J, Jafarpoor M, Rutkove S B., “Assessment of alterations in the electrical impedance of muscle after experimental nerve injury via finiteelement analysis”, IEEE Trans. Biomed. Eng., Vol. 58, 2011, pp. 1585-1591.
4.
Grimnes S and Martinsen O G, “Sources of error in tetrapolar impedance measurements on biomaterials and other ionic conductors”, J. Phys. D: Appl. Phys., Vol. 40, 2007, pp. 9-14.
5.
Keshtkar A, “Virtual bladder biopsy using bio-impedance spectroscopy at 62.500 Hz-1.024 MHz”, Measurement, Vol. 40, 2007, pp. 585-590.
6.
Brown B H, Wilson A J and Bertemes-Filho P, “Bipolar and tetrapolar transfer impedance measurements from volume conductor”, Electron. Lett., Vol. 36, 2000, pp. 2060-2062.
7.
Jones D M, Smallwood R H, Hose D R, Brown B H and Walker D C, “Modelling of epithelial tissue impedance measured using three different designs of probe”, Physiol. Meas., Vol. 24, 2003, pp. 605-623.
8.
Barber D C and Brown B H, “Applied potential tomography”, J. Phys. E: Sci. Instrum., Vol. 17, 1984, pp. 723-733.
9.
Grimnes S and Martinsen O G, Bioimpedance and Bioelectricity Basics, Academic Press, 2008.
10. Geddes L A and Baker L E, Applied Biomedical Instrumentation, Wiley Interscience, NY, 1989. 11. Holder D, Electrical Impedance Tomography: Methods, History and Applications, IOP Publishing, Bristol, UK, 2005. 12. Kwon H and Seo J K, “Local image reconstruction method for EIT with internal electrodes”, Proc. 13th Int. Conf. on Biomedical Applications of Electrical Impedance Tomography, Tianjin, China, April, 2012
