Using deconvolved dispersion parameters for selecting EIT frequencies

The electrical impedance from 100 Hz to 40 MHz was measured for two types of human tumor xenografts. The measurements were made non-invasively, in vivo during hyperthermia treatments. Each impedance spectrum was fit using the sum of two Cole-Cole dispersions. The conductivity at the relaxation frequency (F/sub c/) of each dispersion (/spl sigma//sub Fc/), and the conductivity at 10 MHz (/spl sigma//sub 10M/) were selected for subsequent use. Using the /spl sigma/-ratios /spl sigma//sub 10M///spl sigma//sub Fc/ temperature-dependent effects were minimized and two different aspects of the cellular damage sequence were able to be followed during the hyperthermia treatments. Using each /spl sigma/ and its temperature coefficient, the temperature changes can be simultaneously estimated in the usual way.