Investigation of noninvasive heating system using re-entrant type applicator for malignant brain tumor

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In order to reduce invasiveness of thermotherapy for malignant brain tumors, we have been investigating heating techniques using a re-entrant type applicator, which is a noninvasive heating apparatus.In 2001, we conducted experiments to control the extent of heating. By making some improvements to the trial apparatus and changing the diameter of the re-entrant area, we were able to confirm that the extent of heating can be controlled to a maximum of about 80% of the heated tissue.In 2002, while aiming for clinical use, a round window for inserting patients was placed on the lateral side of the re-entrant type applicator with a diameter of 120 cm and height of 120 cm that had been developed for research use. Initially, using three-dimensional computer simulation, we confirmed that electric field leakage to the outside area was below the allowance. We then measured electric field leakage using a phantom. We were able to confirm that the electric field was within the allowance at least 50 … More cm away from the window. This finding was presented at The 19th Annual Meeting of the Japanese Society of Hyperthermic Oncology.Furthermore, a phantom in the shape of a human body was heated, and the distribution of temperature was measured by infrared thermography. When thermotherapy was conducted at 30 W for 15 minutes, the temperature at the core of the phantom increased by 4.5 degrees, while that at the surrounding area was less than 2 degrees, and no problematic hot spot was seen. This finding was presented at The Annual Meeting of Denshi-johotsushin at Shinetsushibu.In an animal study, a beagle was inserted through the round window on the side of the re-entrant type applicator. Electric field leakage was also below the allowance at least 50 cm away from the window.If re-entrant type thermotherapy is applied clinically, thermotherapy can be repeatedly performed in a noninvasive manner, thus increasing the efficacy of thermotherapy. Noninvasive thermotherapy in the head region using a re-entrant type applicator appears to be promising, and it should be clinically useful. Less