Capacitively Coupled Phase-based Dielectric Spectroscopy Tomography

Yandan Jiang,Manuchehr Soleimani

doi:10.1038/s41598-018-35904-4

Abstract

Impedance imaging is an effective approach for non-intrusively reconstruct the distribution of dielectric parameters inside the region of interest. Most common form of impedance imaging is electrical impedance tomography (EIT), which requires direct contact with the medium via electrodes. In this work we present a novel impedance imaging using capacitive coupling which provides a contactless method, totally non-invasive and non-intrusive, by measuring the phase. There are less attentions in many prior works to the phase information of the voltage/current measurements. This work studies for the first time the capacitively coupled electrical phase spectroscopy for contactless dielectric parameter imaging. A 12-electrode capacitively coupled test phantom and a measurement system were used to obtain the phase measurements within a wideband frequency range from 200 kHz to 15 MHz. Background data with different conductivity levels were investigated in the experiments to show a broad application possibility. The forward modelling was implemented by simulation and the image reconstruction based on phase measurements was implemented with the total variation algorithm. The potentials, possibilities and challenges of such capacitively coupled dielectric spectroscopy tomography with phase data are discussed in this work.

Highlights

Electrical impedance tomography (EIT) is an important part in biomedical and industrial tomography due to its advantages of low cost, high speed and no hazard radiation[1]
Simulation results are obtained with the established model and experimental results are obtained with the real phantom
The conductivity of the background is 0.065 S/m. Phase measurements of these two cases obtained by simulation and by experiments are compared

Summary

Introduction

Electrical impedance tomography (EIT) is an important part in biomedical and industrial tomography due to its advantages of low cost, high speed and no hazard radiation[1]. Current research works and applications of EIT mainly focus on the real part or imaginary part of the measurement for separately conductivity or permittivity imaging[2,3,4] and more importantly by direct contact of electrodes to the object. By using two coupling capacitances, a measurement path can be developed for the AC excitation signal and detection signal can be obtained to implement contactless conductivity imaging[8]. This idea provides good references for other EIT-related research works. A capacitively coupled EIT phantom is developed for phase measurement, with 12 electrodes mounted equidistantly on the outer boundary of an insulating pipe. Where, Cc is the whole equivalent capacitance of the two coupling capacitances C1 and C2. ω and f are respectively the angular frequency and frequency of the excitation signal

Objectives

Methods

Results

Discussion

Conclusion