Study of wireless temperature measurement induction heating system using magnetic properties of Au-coated ferromagnetic implant with low curie temperature

In this paper, we aim to build wireless temperature measurement induction heating system for hyperthermia using "Au-coated Ferromagnetic Implant with Low Curie Temperature (Au-FILCT)". Using this system we clarified the distance-dependent characteristic of voltage used for detecting temperature in heating process of Au-FILCT under high-frequency magnetic field applied. The tumor temperature is measurable utilizing the property in which the magnetism of Au-FILCT changes depending on its temperature. We measured the voltage and temperature of Au-FILCT, while placed at distances of 1.0, 2.0, 3.0 and 4.0 cm from the top surface of the drive coil. We confirmed that the Au-FILCT was heated above the treatable temperature of 45°C within 145.0 seconds up to the distance of 3.0 cm and the accuracy of voltage was improved with the S/N ratio 18.3 dB at 3.0 cm. In addition, the correlation of the voltage with either the temperature or distance was high. All the contribution ratios of their approximate expressions were above 0.97. We propose a method of estimating the temperature from the voltage measured even if the distance to the Au-FILCT is unknown, assuming the core body temperature is stable at about 37°C.