Measurement Error Generated by the Electrode System in Impedance Spectroscopy

The process of introducing a needle into biological tissues is associated with certain difficulties, which can lead to post-injection complications and injuries. The method of impedance spectroscopy is one of the most promising tools for position guidance of a needle in biological tissues. The aim of this paper is to evaluate the measurement error, created by electrical properties of materials, used in the electrode system for impedance study. Using numerical simulation by the finite element method of a low-frequency electric field, the distribution of potentials during the flow of probing currents through the biological tissues was analyzed. Maxwell's equations, Ohm's law and fundamental material relations were used to solve the physical problem. The amplitude and frequency of the probing signal were fixed. By varying such a parameter as the electrical conductivity of the dielectric, the value of the measured impedance changed. The resulting curve made it possible to determine the allowable conductivity value at which the electrode system create a minimum measurement error. The results of this study may be useful in the development of electrode systems with different geometric characteristics and the choice of materials for conductors and dielectrics.