Real-time extraction of tissue impedance model parameters for electrical impedance spectrometer

This paper presents a new algorithm for real-time extraction of tissue elec trical impedance model parameters from in vivo electrical impedance spectro scopic measurements. This algorithm was developed as a part of a system for muscle tissue ischemia measurements using electrical impedance spectroscop y. An iterative least square fitting method, biased with a priori knowledge of the impedance model was developed. It simultaneously uses both the real and imaginary impedance spectra to calculate tissue parameters R-0, R-infi nity, alpha and tau. The algorithm was tested with simulated data, and duri ng real-time in vivo ischemia experiments. Experimental results were achiev ed with standard deviations of sigma(R0) = 0.80%, sigma R-infinity = 0.84%, sigma(2) = 0.72%, and sigma(tau) = 1.26%. On a Pentium II based PC, the al gorithm converges to within 0.1% of the results in 17 ms. The results show that the algorithm possesses excellent parameter extraction capabilities, r epeatability, speed and noise rejection.