In capacitive heating, an air gap between a human body and a bolus often causes a concentration of a current and brings an injury.An air gap frequently disrupts a treatment and inhibits an output power of the hyperthermic device. Therefore, an air gap filler material has been developed.
In this paper, we calculated some models to investigate relations between properties of air gap filler materials and their heating characteristics. In the process, we created several analytical models, which have different contact situations between the human body and the bolus. In the gap filler material insertion models, we developed various types of models, which have different electrical constants and sizes.
We calculated current distributions and the SAR distributions of these analytical models. From the results of calculations, we found that an air gap affects the heating characteristics and an air gap filler material can improve heating patterns. Moreover, we confirmed that an air gap filler material, which has low conductivity and larger diameter than bolus, is the most effective in this scenario.

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