Analysis of Sensor Field in Electromagnetic Tomography

Electromagnetic tomography (EMT) is a recent imaging technique. Its purpose is to determine the distribution of electrical conductivity and magnetic permeability in a given region of interest. EMT is based on the principle of electromagnetic induction. This distribution is computed from the measurements of the induced voltages at several coils placed around the region, which are produced by the application of different excitation patterns . Usually images are obtained through inversion of the projection data. The measurement sensitive field of EMT sensor is affected greatly by medium distribution. Such soft field character is one of major difficulties in image reconstruction of EMT. Through the analysis of sensitivity distribution, the rule of soft field is discussed. The results show that different resistance medium distribution affects the sensitivity polarity slightly, but the change of sensitivity value is related not only to medium distribution, but also to its location in sensitivity filed.