Spatial Resolution in the Electrical Impedance Tomography for the Local Tissue

Electrical impedance tomography (EIT) is one of the medical tissue diagnosis devices and it creates a two- or three-dimensional image of electrical impedance distribution in a living tissue. It is used for imaging the information of tissue structures, and physiological functions and states of the tissue. However, there are several problems to achieve the practical use of EIT, which are an inverse algorithm for estimating parameters and electrode structure and so on. EIT is calculated from impedance data, which is measured non-invasively by surface electrodes. Therefore, it is important to choose a proper electrode structure to realize a practical EIT measurement system. In this study, we used a electrode structure, called "divided electrode", which is proposed for a short time measurement of bio-impedance in a cross section of the local tissue. Its capability is examined by computer simulations, where a distributed equivalent circuit is used as a model for the cross section tissue. Estimation of impedance parameters is carried out by use of the Newton method. The objective of this study is to examine the spatial resolution on the circuit model. Moreover, the current flowing in the circuit model is examined.