A Temperature Measuring System with an Implantable Sensor for the Hyperthermia

We have developed a temperature measuring system with an implantable sensor for the hyperthermia application. As the sensor does not require a battery, it can be implanted in a body for a long term and used repeatedly. The sensor consists of a coil and a quartz resonator whose resonance frequency varies with ambient temperature. The resonance frequency of the sensor can be measured sensitively from outside of the body by applying frequency modulated RF electromagnetic field. A microcomputer in the measuring system converts the resonance frequency to the corresponding temperature. Furthermore, the temperature data are displayed on a CRT display and stored in a floppy disk automatically. With this system, we have measured the temperature ranging from 35 to 50°C with errors less than ±0.1°C. The system operated properly while it was heated with 500W RF electromagnetic generator