The design of an indirect heating source for the treatment of malignant brain tumors is presented. A high Q resonant tank working at 25 kHz generates a magnetic field of 16,000 ampere-turn/meter (peak) which is used to heat metallic implants by a combination of hysteresis and induced current heating. The resonant tank is used in a feedback loop of the power driver to maintain the driver at the resonant frequency, thus minimizing the power losses that inevitably occur in open loop systems due to reference oscillator drifts and/or varying load and tank conditions. Because of the high field strengths required and the relatively small power dissipation that occurs in the metallic implants, the overall system design differs substantially from standard induction heating applications.