Magnetic hyperthermia with magnetic nanoparticles (MNPs) has been introduced to selective treatment of tumor 1,2 and the MNPs also has demonstrated diagnosis 3, 4. For non-invasive treatment, a therapeutic system with a temperature monitoring that can avoid overheating in normal tissues is of vital importance. We have developed a temperature monitoring/control system with an optical fiber temperature probe in vivo 2. However, the optical fiber involves an invasive measurement due to the contact with the body. In this study, we have developed a wireless temperature monitoring system by utilizing the combination of magnetic harmonic signals of the MNPs for clinical trials. Figure 1 shows the developed wireless monitoring system with Resovist® (a clinically approved MNP). Under the application of alternating magnetic fields, the detected harmonics were analyzed to extract only temperature-dependent signals. Figure 2 shows the measured temperature of Resovist® phantom. We achieved an accurate measurement with an error of 0.18°C (Fig. 2(a)). For practical use on breast/oral cancer, a detectable distance of 10 mm is required. We measured the accurate temperature at a 10 mm distance (Fig. 2(b)). To demonstrate the feasibility toward clinical trials, we investigated the dependency on the detectable distance and the amount of Resovist®. The error is less than 0.5°C in a 10 mm distance (Fig. 2(c)). Resovist® travels to the whole body from the injection site via the lymphatic system, resulting in a decrement of the amount at the injection site. Our system can measure the correct temperature regardless of Resovist® amount (Fig. 2(d)). The results indicate that our system can apply to clinical trials. We will pursue further study of a temperature monitoring system under magnetic hyperthermia treatment.

References:

1 D. Kouzoudis et al., frontiers in Materials 8, 638019 (2021)
2 A. Shikano et al., T. Magn. Soc. Jpn. (Special Issues) 6, 100-104 (2022).
3 M. Sekino et al., Scientific Reports 8, 1195 (2018)
4 K. Taruno et al., J. Surg. Oncol. 120, 1391 (2019)