Electrical Impedance Tomography of Known Targets

Electrical impedance tomographs (showing magnitude and phase) of known, laboratory-scale targets are reported. Also presented is a generalization of a proven electrical resistance tomography (ERT) algorithm, to account for electrical impedance. Three methods are used to reconstruct electrical impedance data and their results compared. The first two methods employ approximate relationships between the measurements and reconstructed tomogragh while the third approach employs fully complex algebra to account for the real and imaginary components of electrical impedance data. The electrical impedance tomography (EIT) and the perturbation analysis (PA) algorithms provided useful magnitude and phase images for the frequency range of 0.0625 to 64 Hz; images for 256 and 1024 Hz are also presented but these were not reliable. The frequency effect (FE) approach did not produce reliable phase images. Comparisons of the ERT and EIT magnitude images show that both methods provided equivalent results for the water blank, copper rod and PVC rod targets. The EIT magnitude images showed better spatial resolution for the sand-lead mixture target. Phase images from both methods located reasonably well anomalies of both high and low contrast induced polarization (IP) and provided better spatial resolution than the magnitude images. When IP was absent from the data, the EIT and PA algorithms reconstructed phase values consistent with the data noise levels.