Modeling and experimental validation of parasitic capacitance effects on emulated bioimpedance measurements with high-impedance residuals

摘要

Parasitic capacitances and high-residual impedances (typical of electrode/tissue interfaces) have significant effects on estimated electrical impedances of tissues under study. This leads to deviations (especially at high frequency) from the true tissue impedance. This work outlines the circuit theory describing estimation errors occurring when one and two parasitic capacitances are present in tetrapolar electrode configurations typical for bioimpedance measurements. The described circuit theory was validated using both simulations and measurements of a fabricated printed circuit board that implemented the tetra-polar model. Using the presented model, correction procedures using (a) measurements of the source and sink excitation currents and (b) averaging measurements of forward and reverse electrode configurations have been validated in simulation showing reductions in the estimation errors at frequencies greater than 1 MHz.