Wireless temperature measurement based on magnetic harmonic signal during magnetic heating operation for hyperthermia

We developed a wireless temperature measurement method based on magnetic harmonic signals during magnetic heating and evaluated highly concentrated magnetic nanoparticles (MNPs) for hyperthermia applications. XRD confirmed that the iron oxide composition of Resovist® remained unchanged after concentration, while TEM and DLS analyses demonstrated reversible dispersibility between concentrated and diluted states. Magnetization measurements showed an increase in saturation magnetization, and the AC hysteresis loop area of fourfold-concentrated Resovist® was 3.8 times larger than that of the original sample, indicating enhanced heating efficiency. The detectable distance and volume for temperature measurement improved from 5 mm to 12 mm and from 10 µL to 5 µL, respectively. The developed system achieved noninvasive temperature measurement with an error of 0.07°C and constant-temperature control with a deviation of 0.56°C, demonstrating sufficient precision for biomedical applications.