Multiplexing Error and Noise Reduction in Electrical Impedance Tomography Imaging

Abstract

Electrical Impedance Tomography design can be simplified to obtain a low cost 16 electrodes edema monitoring clinical instrument by using voltage measurement multiplexing. Multiplexers introduce errors, which we have estimated by consecutive phantom measurements both using voltage multiplexers and by selecting the electrodes by hand, all other things being the same. Noise is taken care of by averaging. The EIDORS reconstruction of the phantom with multiplexed measurements is compared to the hand-selected electrode measurements reconstruction. The difference image obtained is considered an estimation of the multiplexer induced error. This measurement error is subtracted from the multiplexed object measurement matrix, giving a modified reconstruction which is closer to the hand-selected electrodes measurement based reconstruction than the multiplexed reconstruction. The quality factor of the uncorrected multiplexer obtained image of 57% is increased to 83% which is the best increase of three methods described. This suggests the benefit of a “calibration” phase for all 16 electrodes, prior to EIT reconstruction, using a set-up-specific “error matrix” to correct the data matrix before submission to the reconstruction method.