IMPEDANCE SPECTRA OF TUMOR-TISSUE IN COMPARISON WITH NORMAL TISSUE - A POSSIBLE CLINICAL-APPLICATION FOR ELECTRICAL-IMPEDANCE TOMOGRAPHY

Electrical characteristics of living tissues have been investigated fo r a long time in the search for further methods to complement the trad itional investigations of pathology and physiology. Tumour tissue has been shown to exhibit a larger permittivity and conductivity than norm al tissues. This might be associated with the fact that tumour cells h ave a higher water content and sodium concentration than normal cells, as well as different electrochemical properties of their cell membran es. To our knowledge only a few contributions on this subject have bee n published. This study describes an additional application on measure ments of the complex impedance of tumour and normal tissues, in order to compare the impedance features of the two tissue types. The tissue sample is placed in a measuring cell in which the temperature is contr olled. The measuring cell is connected to an impedance meter able to m easure the complex impedance in terms of real and imaginary part curve s for frequencies from 1.5 kHz to 700 kHz. The four-electrode principl e is used with the current injected by the outer electrodes and the vo ltage difference measured between the inner electrodes. The current ca n be altered up to 1 mA. The instrument can be calibrated with known r esistance and capacitance networks connected to the input of the instr ument in order to minimize the measurement errors. The calibration rou tine uses a polynomial adaptation and can be applied interactively. Me asurements performed by the instrument show promising results. Prelimi nary results show that this method can be extended to a new applicatio n for detection of tumour tissue by electrical impedance tomography (E IT).