Estimation of Multi-Layer Tissue Conductivities from Non-invasively Measured Bioresistances Using Divided Electrodes

Xueli ZHAO  Yohsuke KINOUCHI  Tadamitsu IRITANI  Tadaoki MORIMOTO  Mieko TAKEUCHI  

IEICE TRANSACTIONS on Information and Systems   Vol.E85-D   No.6   pp.1031-1038
Publication Date: 2002/06/01
Online ISSN: 
Print ISSN: 0916-8532
Type of Manuscript: PAPER
Category: Medical Engineering
bioimpedance,  FEM,  FDM,  divided electrodes,  tissue conductivity,  

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To estimate inner multi-layer tissue conductivity distribution in a cross section of the local tissue by using bioresistance data measured noninvasively on the surface of the tissue, a measurement method using divided electrodes is proposed, where a current electrode is divided into several parts. The method is evaluated by computer simulations using a three-dimension (3D) model and two two-dimension (2D) models. In this paper, conductivity distributions of the simplified (2D) model are analyzed based on a combination of a finite difference method (FDM) and a steepest descent method (SDM). Simulation results show that conductivity values for skin, fat and muscle layers can be estimated with an error less than 0.1%. Even though different strength random noise is added to measured resistance values, the conductivities are estimated with reasonable precise, e.g., the average error is about 4.25% for 10% noise. The configuration of the divided electrodes are examined in terms of dividing pattern and the size of surrounding guard electrodes to confine and control the input currents from the divided electrodes within a cross sectional area in the tissue.