Design of electrode array for impedance measurement of lesions in arteries.

Use of impedance catheters can provide additional information about the composition and the morphology of early plaques in arteries. However, for a correct interpretation of the impedance data recorded inside a vessel, the extra-vessel conditions should not influence the measurement results. In this paper, we estimate the influence of the extra-vessel conditions on the impedance measurement of a vessel wall by using FEM simulation and a two-layer model. Therefore sensitivity fields are simulated. The simulations are validated by experiments and compared to analytical solutions. Further, the influence of the inner radius of a vessel on the measurement result is determined by FEM simulations. From experiments based on the two-layer model, it is found that the apparent resistance depends on the thickness of the first layer and the separation distance of the electrode structure. The measured result corresponds to the results of the FEM simulations, whereas the analytical solution assuming point electrodes is different from the measurement and simulation results. Under the assumption of homogenous and linear volume conductors, the FEM simulated distributions of sensitivity fields are determined. The inner diameter of the artery has no influence on the measurement results. The FEM simulation can support the design of electrode configuration and geometries for impedance catheters.