It is difficult to heat deeper tumors using microwaves, because microwaves decrease rapidly in the muscle tissues. Nevertheless, it is possible to increase the penetration depth by controlling the electric field intensity and phase distribution on the aperture of the applicator in the range of low microwave frequency region.
In this paper, we developed the applicator at 430MHz which is partially loaded by the dielectric in the center and is loaded by the ferrites on the both sides of the dielectric. As ferrite permeability can be thanged by applying the external D.C. magnetic field to the ferrites, the electric field distribution on the aperture of the applicator can be changed. Therefore, the radiated microwave from the applicator can be controlled only by changing the D.C. magnetic field intensity to the ferrites. The experimental results of the heating of phantom modeling material show that the applicator is available for the microwave heating for hyperthermia.

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RF capacitive heating has been widely used in clinic. In order to heat a deep seated tumor effectively and safely, we must pay attention to overheating of the fat layer near the skin surface and also just under the edges of applicators during hyperthermia treatment.
We have investigated characteristics of RF capacitive heating with typical applicator arrangements by computer simulation. In these analyses, temperature dependence of the blood flow rate through tissues are partially taken into consideration.
Here, we present these results and it is confirmed that we should use the pair applicators 1.5 times larger than the gap length between them.

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We studied the effectiveness of hyperthermotherapy in the treatment of deep abdominal tumors using Thermotron-RF8.
Although the endotractal heating has been reported to be an effective therapy for esophageal cancer, it is difficult to obtain homogeneous distribution using this technique. In order to investigate methods of obtaining homogeneous distribution of heat during extracorporeal heating of the esophagus, a capacitive heating device, Thermotron-RF8, was used for basic trial on agar phantoms and swine. Heat was applied for 20-30 min. at 500-600 watts.
1) Trial were performed on models of the esophagus constructed by boring a cylindrical channel with a 2cm radius through the center of an agar phantom. Temperature distribution during hyperthermia was measured by thermography in the presence and absence of potato starch dissolved in physiological saline within the channel. 2) For trials performed in the swine model, temperature sensors were inserted via the stomach and placed at 3 sites within the lower esophageal lumen and at one site touching the esophageal wall. After placement of a double balloon catheter within the esophagus, the tempera-tures of the luminal surface and esophageal wall measured during application of hyperthermia in the presence and absence of potato starch within the esophageal lumen.
1) In agar phantoms, not containing starch, the RF wave was concentrated at the latemal portion of the channel, and hot areas formed. In filled channels, there was homogenous distribution of heat. 2) In swine esophagi, intraluminal temperatures in filled showed significant increases compared with that in empty lumina, and increases in esophageal wall temperatures in both filled and empty lumina showed similar patterns with no significant differences. In addition, in empty lumina temperatures of the wall showed significant increase compared with that of the lumen. In the filled lumina, temperatures in both the wall and the lumen showed no significant differences. These results indicate that more homogenous temperature distribution is obtained when the lumen is filled than when it is empty, and that measurement of the temperature within the lumen can be used as an indirect measurement of wall temperature.

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Between May 1986 and September 1991, 104 patients of advanced or recurrent cancer were treated with combination therapy of hyperthermia and irradiation at UOEH hospital. Twenty seven patients had superficial tumors and 77 patients had deep seated tumors. They were irradiated with conventional fractionation. Hyperthermia was performed within 30 minutes after each irradiation once or twice a week using RF capacitive heating equipment, Thermotron RF-8. Total number of heating was 791 times. The most frequent side effect was pain under the electrode. It was observed in 444/791 (56 %) but most of them were mild and severe pain was seen only in 2 %. Burn due to heating was observed in 13 patiens (13 %). Severe side effect was observed in 9 patients consisting of 4 cases of ileus needing hospitalization, 3 cases of bleeding from intestine and tumor and 2 cases of intestinal fistula. It was not clear whether those damages were due to the heating itself or tumor growth. No patients had cardiovascular side effects.

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To prevent the leakage of Radio Frequency wave (RF wave) during hyperthermia, magnetic material was used. A ferrite core in troidal shape as a magnetic material was put into the coaxial cable between Endoradiotherm100A^R and internal applicater. About 3.5-4dB loss of leakage was obtained.
This method might be effective for decreasing the leakage of RF wave.

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