In vivo measurement of temperature dependent permittivity of tissues in asmall region

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A new method for measuring the temperature dependence of tissue permittivity in the small region has been developed by use of the small coaxial probe, vector network analyzer, and RF power source. The developed coaxial probe is used not only for permittivity measurement but also for increasing temperature in the small region of measurement. Temperature coefficients of the permittivity are calculated from complex permittivity measured at different temperatures. Throughout the research, we have obtained the following results.1. Region of the measurement by the coaxial probe has been clarified.2. The coaxial probe equipped with four small temperature sensors has been developed for permittivity measurement and heat generation in the small region of interest.3. The measuring method of the temperature distribution under the coaxial probe has been developed.4.We have proposed a method to estimate the average temperature change in the region of measurement.5.The estimated temperature coefficients show a good agreement with temperature coefficients of complex permittivity of the phantom model of simulated tissues obtained by the other method.In conclusion, we have developed the method for in vivo measurement of temperature coefficient of the tissue permittivity. The method can practically be used for measuring temperature dependent permittivity of various tissues. Information on the temperature dependence is utilized for non-invasive temperature mapping by the microwave computed tomography and control of electromagnetic hyperthermia equipments.