Development of Multichannel Thermometer with Implantable Sensors for the Hyperthermia

Up to date, thermocouple sensors have been applied in temperature monitoring during hyperthermia. However, using thermocouple sensors, infection and metastasis may be caused by inserting and removing the sensing wires. We have therefore developed a completely implantable temperature sensor which does not require a battery. The sensor consists of a coil which transmits signals to the receiver coil outside the body and a quartz resonator. And its resonance frequency varies with ambient temperature. The resonance frequency to the corresponding temperature can be measured from the outside of the body. Heat accumulates not only in the cancer but also in the normal tissue with RF hyperthermia system. Therefore, a multichannel thermometer with implantable sensors having different resonance frequency each other has been developed in the present. Sensors are implanted at various sites and sensor coils are gathered in a bundle pairing with a receiver coil. Then, the resonance frequency of sensors is measured in order. If the difference among the resonance frequency of sensors is higher than 100kHz, errors caused by interference among sensors will be negligible. The temperatures at 10 points can be sequentially measured with this thermometer and the required time is about one second per channel