Experimental evaluation of image plane selectivity in electrical impedance tomography

The problem of image plane selection in electrical impedance tomography is discussed from a practical standpoint. Spherical nonconducting targets (1.9 cm radius) are placed in a saline-filled tank similar in size to an adult human torso. Impedance data are acquired with a computer-based system that sequentially applies current to pairs of electrodes located on two horizontal planes and records voltages simultaneously from 16 electrodes on a third, central, plane, Sensitivity curves relating the contrast produced on the reconstructed images by a target to the vertical position of the target are determined. For any radius position within a critical radius, it is found that sensitivity is maximum when the target is in the plane of the recording electrodes (z=0) and decreases monotonically as it is moved away. Two experiments illustrate how sensitivity curves could be used to predict, in a first approximation, the projection of a 3-D conductivity distribution on the z=0 plane