Four-Terminal Imaging Using a Two-Terminal Electrical Impedance Tomography System

Electrical impedance tomography (EIT) is a promising visualization measurement technique to reconstruct media distribution in a region of interest (ROI) through impedance measurements on its boundary. In this paper, a two-to-four-terminal mode is proposed for a two-terminal EIT system to take advantage of the four-terminal imaging mechanism. Using the two-to-four-terminal mode, data are acquired using the two-terminal EIT system, whereas the imaging mechanism is based on the four-terminal mode. To realize four-terminal imaging using a two-terminal EIT system, the mapping formulas of data from the two- to four-terminal mode and vice versa are derived. A novel imaging method based on two-to-four-terminal mode is proposed to decrease the ill conditionedness of the relevant inverse problem and implemented with the conjugate gradient iteration algorithm and the Tikhonov regularization algorithm, respectively. Simulation and experimental results validate the feasibility and effectiveness of the proposed method in reconstructing inclusions within the ROI clearly and exactly in both shape and location. Compared with the method based on two-terminal mode, the quality of the images reconstructed using the proposed method can be improved in terms of contrast, resolution, and antiartifact, i.e., reducing the artifacts in the reconstructed images, especially when distinguishing complicated distributions. Meanwhile, the imaging speed is also increased. Moreover, the availability of four-terminal imaging mechanism in a two-terminal EIT system makes it more flexible to choose an appropriate mode according to the application requirements and available instruments.