Effect of electrode size on impedance images of two- and three-dimensional objects

The sensitivity of an impedance imaging system to small cylindrical inhomogeneities in two-dimensional (2-D) and three-dimensional (3-D) saline tanks was studied for different height electrodes and different height targets. Experimental results were compared with analytical models. Inhomogeneities in the 3-D tank having limited vertical extent were detected by electrodes of vertical size comparable to that of the inhomogeneity. Taller electrodes had increased sensitivity to short targets to only a limited extent. When the electrode height was more than twice that of the target, sensitivity decreased or remained the same with further increases in electrode height. The system was less sensitive to inhomogeneities in the 3-D tank than to those in the 2-D tank. The distinguishability of conductors was greater than that of insulators in the 3-D tank, and the opposite was true in the 2-D tank, consistent with an analytical result.