Simulation study for the non-contact measurement of the impedance of biological tissue using an axial gradiometer

The measurement of the impedance of biological tissue can be a non-invasive method to find new data of diagnostic relevance. A system for a noncontact measurement of the electrical impedance of biological tissue is presented. The system consists of an excitation coil and two sensing coils coupled together as a gradiometer. The excitation coil is driven by an alternating current. Due to this alternating magnetic field eddy currents are generated in the tissue that create a secondary magnetic field. Due to the geometrical arrangement, the induced voltage of the secondary field in the upper and the lower coil is different. Numerical experiments are carried out to calculate the fields, eddy current distributions and induced voltages. Hereby tests with different frequencies of the excitation current and different conductivities of a tissue block are used.