Heating Characteristics of RF Capacitive-type Heating Device

Abstract

RF Capacitive-type heating device (8 MHz) manufactured by Yamamoto Vinita Co., Ltd., improved the generator from EX edition with self-excited oscillator using tube to GR edition with solid-state amplifier using crystal oscillation, which led to downsizing. To prove heating characteristics of the new device, we compared the heating performance of both devices on basic heating characteristics and assumed clinical use using agar phantoms. 1) Waveforms of RF generated by both devices were similar, and those were not distorted. 2) In the experiment using a phantom for measuring the heating electricity, both devices were able to uniformly heat the phantom, and those heating efficiencies were 63 and 64%, respectively. 3) A phantom was sandwiched between a pair of electrodes, the diameter of lower electrode was fixed at 30 cm, and that of upper electrode was changed from 30 to 7 cm. The range of the heating area became shallower as the electrode became smaller. Those phenomena were same on both devices. 4) In case of a protrusion on upper side of the phantom, the temperature rise of the protrusion was higher than its surroundings. Those tendencies were same on both devices. 5) When there was an air cavity in the phantom, the temperature rises in the phantom near the air cavity facing the electrode was small, and that not facing the electrode was large. Those phenomena were the same on both devices. 6) When there was a bone in the phantom, the temperature rises in the phantom near the bone facing the electrode was small, and that not facing it was large. The temperature of the bone itself rose a little. Those phenomena were same on both devices. 7) Regardless of electrodes set in parallel or not parallel, the temperature distributions of the depth direction were same. But the temperature rises in one side of the phantom at the closer distance between two electrodes rose larger than the opposite side. Those phenomena were same on both devices. From the above, the heating device GR edition using the solid-state amplifier is upward compatible with respect to the heating device EX edition using the oscillating tube.