Measurement of electrical impedance in different ex-vivo tissues.

Bioimpedance allows living tissues characterization and detection of pathological states. Although in previous years several methods have been proposed to assess bioimpedance, many instruments used in studies of living tissues characterization are commercial devices designed for the measurement of components or electronic circuits and therefore the measurement of biological tissues can be affected by electrical polarization. In order to test if electrical impedance spectroscopy may be helpful in providing further information about the structure and the properties of tissues, an impedance meter for living-tissues, able to avoid polarization, was developed. Subsequently, ex-vivo impedance measurements were performed by placing a needle-probe into 6 tissues (heart, kidney, lung, muscle, liver and fat) of 3 rabbits. Impedance was analyzed in terms of modulus and phase. In the range 2-10 kHz, considering both modulus and phase, it was possible to discriminate each tissue with statistical significance. In the lower considered range of frequencies (i.e., 10-100 Hz and 200-1000 Hz) this was not always the case. We conclude that the detailed analysis of modulus and phase in the frequency range of 2-10 kHz, by using an ad-hoc device able to avoid electrical polarization, allows to discriminate between several healthy living tissues.