Improvement of SNR in magnetic particle imaging based on magnetization signal generated by external vibration of magnetic nanoparticle

Recently, magnetic particle imaging (MPI) has been proposed as a newmedical imaging technology for diagnosing cancer and cardiovascular diseases. When magnetic nanoparticles (MNP) are injected into a living body, the MNP circulate in the blood vessels and accumulate in a cancer cell. In MPI, the MNP distribution is reconstructed by detecting the magnetization signals generated by changing the magnetization state of the MNP using an externally applied alternating magnetic field. However, in this signal detection method, because both the magnetization signals and the alternating magnetic field are simultaneously detected, it is necessary to separate them. Consequently, the same component with the same frequency as the alternating magnetic field is removed, and this component constitutes the majority of the magnetization signals. Hence, the signals of the MNP after separation become small and the signal-to-noise ratio (SNR) deteriorates. Therefore, we propose a magnetization signal detection method based on vibration of the MNP, without using the alternating magnetic field. In this method, because it is not necessary to separate the component with the same frequency as the alternating magnetic field from the magnetization signals, larger signals can be detected compared to that obtained by the conventional method, and the SNR can be improved. In this study, in order to confirm the efficacy of the proposed method, the SNRs of the conventional and the proposed methods were evaluated experimentally. Based on the results obtained, we confirmed that the SNR of the proposed method improved by 11.3 dB compared to the conventional method. © 2019, Japan Soc. of Med. Electronics and Biol. Engineering. All rights reserved.