The temperature dependency of complex permittivity of biological tissues was measured and much information could be derived from a series of preliminary experimental results.
The temperature coefficient of conductivity was larger than tht of dielectric constant and fairly large temperature coefficients were observed in fatty tissues rather than nonfatty tissues. Although it depends on the frequency of a heating equipment, real-time control of the equipment may be required to keep the best condition for the treatment (e. g. a desirable temperature pattern). This also means that the temperature dependency must be taken into consideration in the computation of temperature distributions for planning of the treatment. The temperature dependency of the permittivity may be utilized for noninvasive temperature monitoring in the active imaging, but at the same time, it is undesirable in a passive method such as microwave radiomtry.
