A Fundamental Numerical Analysis for Noninvasive Thermometry Integrated in a Heating Applicator Based on the Reentrant Cavity

To improve the efficacy of hyperthermia treatment, a novel method of noninvasive measurement of body temperature change is proposed. The proposed technology, thermometry, is based on changes in the electromagnetic field distribution inside the heating applicator with temperature changes and the temperature dependence of the dielectric constant. In addition, an image of the temperature change distribution inside a body is reconstructed by applying a computed tomography (CT) algorithm. The proposed thermometry method can serve as a possible noninvasive method to monitor the temperature change distribution inside the body without the use of enormous thermometers such as in the case of magnetic resonance imaging (MRI). Furthermore, this temperature monitoring method can be easily combined with a heating applicator based on a cavity resonator, and the novel integrated treatment system can possibly be used to treat cancer effectively while noninvasively monitoring the heating effect. In this paper, the phase change distributions of the electromagnetic field with temperature changes are simulated by numerical analysis using the finite difference time domain (FDTD) method. Moreover, to estimate the phase change distributions inside a target body, the phase change distributions with temperature changes are reconstructed by a filtered back-projection. In addition, the reconstruction accuracy of the converted temperature change distribution from the phase change is evaluated