Harmonic detection and noise suppression in a magnetic nanoparticle thermometer

Magnetic nanoparticle (MNP) thermometry will be necessary for safe therapeutic implementation of magnetic nanoparticle hyperthermia, a developing cancer treatment. One realization of a MNP thermometer works by detecting harmonic signal (the fundamental f and 3f harmonics) generated by MNPs exposed to ac magnetic field. In this paper, we aim to measure accurately the harmonic signal in a MNP thermometer, which are contaminated with, or even buried in strong noise including wideband Gaussian, and industry frequency noise. The relations between the temperature error of a MNP thermometer and the measurement error of the harmonic signal are first studied. Furthermore, the theoretical model of a synchronous detector for measuring harmonic signal is then described in detail. Next, the ability of the synchronous harmonic detector to decrease noise (Gaussian, and industrial frequency noise) is assessed from simulations. Last, the experimental results showed effectiveness of the synchronous harmonic detector used in the MNP thermometer.