Development of RF interstitial capacitive hyperthermic system for malignant brain tumor.

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In order to establish the hyperthermic system of RF interstitial capacitive heating, we studied development of RF antennas, operative technique for implant and clinical appling. A Pase I/II clinical trial has been initiated to determined the feasibility of an interstitial hyperthermia using 13.56MHz radiofrequency (RF) antennas in the treatment of malignant brain tumors. The needle type applicator (RF antennas) with diameter of 1.0mm was developed. A single or multiple (2-4) antennas were inserted into the brain tumor using a CT-guided stereotactic apparatus. The temperature of the brain and the tumor were monitored by the copper-constantan thermocouple sensors. The RF interstitial hyperthermia was performed on 30 patients with malignant brain tumors, 22 malignant gliomas (10 primary and 12 recurrent), 7 metastatic tumor and 1 malignant lymphoma. The rim of the tumors which were defined by contrast enhanced CT was heated at 43.0ﾟC for 60 minutes. The heating was repeated 3-9 (mean 5) times, once or twice a week, combined with conventional radiation or chemotherapy. The recurrent gliomas were treated with heat alone. The patients complained no local pain or heat sensation and well tolerated the repeated heating. No major complication occurred except liquorrhea in 2 cases, subcutaneous infection in one case, intratumoral hemorrhage in one case and trasient neurological symptoms in 2 cases. The anti-tumor effects were evaluated by CT and the treated tumors showd CR in 8, PR in 10, ST in 9 and PD in 3 cases, respectivery. In most of CR cases, the perifocal low density lesion also disappeared. These preliminary results indicated that the RF interstitial hyperthermia seemed to be effective in treatment of malignant brain tumors, this technique is less invasive and the tumors in aged or poor risk patients as well as deep-seated tumors can be good candidates for the application.