The problem of finding the optimum current under different constraints in electrical impedance tomography is cast into a non-linear optimization problem. Optimum currents are investigated for a two-dimensional cylindrical body with a concentric or an eccentric inhomogeneity under the constraints of constant dissipated power and constant total injected current. For a concentric inhomogeneity, it is shown that the opposite drive results in a better distinguishability than the cosine current pattern under the constant-injected-current constraint. The results for the concentric case are extended to the eccentric case directly using the properties of the conformal transformation and of the constraints involved. Distinguishability and the minimum detectable object size achieved by the optimized currents are compared with the ones achieved by the cosine current pattern for conductivity distributions with the concentric and eccentric inhomogeneity.

The distinguishability of a discrete coil induced current electrical impedance tomography system is analysed. The solution methodology of the forward problem of this system is explained. An optimization procedure using this forward problem solution is developed to find optimum currents that maximize the distinguishability. For the concentric inhomogeneity problem, it is shown that the coil currents can be optimized to focus the current density in any desired location, in the field of view. Optimum coil currents under the constraints of limited peak coil currents and limited total power are determined. Examples that demonstrate the performance of the system are presented.

An accurate Method of Moments (MOM) model is developed and implemented for the analysis of the linearly tapered slot antenna (LTSA). The model employs an unequal size reactangular sectioning for conducting parts of the antenna. Piecewise sinusoidal basis functions are used for the expansion of conductor current. The effect of the dielectric is incorporated in the model by using equivalent volume polarization current density and solving the equivalent problem in free space. The feed section of the antenna including the microstripline is handled rigorously in the MOM model by including slotline short-circuit and microstripline currents among the unknowns. Comparison with measurements is made to demonstrate the validity of the model for both the air case and the dielectric case. Numerical results for the effect of the dielectric permittivity are presented. 0

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A distinguishability measure is defined for magnetic resonance-electrical impedance tomography (MR-EIT) based on magnetic flux density measurements. This general definition is valid for 2D and 3D structures of any shape. As a specific case, a 2D cylindrical body with concentric inhomogeneity is considered and a bound of the distinguishability is analytically formulated. Distinguishabilities obtained with potential and magnetic flux density measurements are compared.