Body motion artifact reduction method using rotary scanning for accuracy improvement of wireless temperature measurement

In hyperthermia treatment, the accurate temperature measurement of tumor region is vital to determine the therapeutic effectiveness of heating. Conventional methods require thermal probes to be inserted invasively into tumor region. However, by using Ferromagnetic Implant with Low Curie Temperature (FILCT) as thermal probe, we have developed a wireless temperature measurement method that can noninvasively measure the temperature of tumor region from outside of the body. To make the approach feasible in clinical settings, challenges remain when dealing with body motion artifact. When the material is injected into tumor region, the relative position between the magnetic field supply and detection (MFSD) unit and the material is supposed to fluctuate with periodic respiration and heartbeat. In physical experiments, the FILCT temperature cannot be detected, because the detection voltage was buried by the artifact noise (SN ratio=-3.1 dB). Hence, this study proposed a body motion artifact reduction method by rotating scanning the MFSD unit in a different period cycle from body motion. By extracting the power spectrum synchronized with the rotary scanning, we confirmed that regardless of presence of body motion, the change of the power around Curie point is sufficiently large to detect whether treatment temperature has been reached.