RC two-phase electrical impedance imaging system

Electrical impedance imaging is one of the computed tomography techniques for reconstructing the image of internal resistivity or conductivity distribution using the electrical measurements made on the periphery of a body. There are two components of impedance for the tissues, the resistive and reactive parts, respectively. In this article, a microcomputer-based electrical impedance imaging system was designed for producing both the resistivity and permittivity images of a cross-section inside the body. The current patterns modulated by the 15 KHz sinusoidal signal were applied to the surface of the body via an array of 32 electrodes. The resulting voltage patterns were then measured both in-phase and quadrature using the same array of electrodes. From the applied currents and measured voltages, the images of resistivity and permittivity distributions could be produced using the same reconstruction algorithm. This algorithm was also developed based upon the Newton-Raphson method and finite element method. Both the system and reconstruction algorithm were validated with a simulation saline phantom containing insulators and conductors.