VP15-03 Direct Magnetic Field Compensation with Multichannel Digital-to-Analog (D/A) Converter in Magnetic Particle Imaging
Creators: Tomoki Matsushita
Teruyoshi Sasayama
and Takashi Yoshida
Publisher: name: IEEE
Year: 2025

Magnetic particle imaging (MPI), which displays the concentration distribution of magnetic nanoparticles (MNPs), has gained attention as a new diagnostic imaging technology [1]. One problem with MPI is that it requires a strong gradient field, that causes peripheral nerve stimulation. In this study, the concentration distribution was obtained by arranging the detection coils in an array without a gradient field [2]. The voltage from the detection coil also contained a fundamental component derived from the external magnetic field, that interfered with the measurement. To solve this problem, a single-channel D/A converter and variable resistors were used to compensate for the fundamental component [3]. However, this compensation method is inaccurate. In this study, we propose a new compensation circuit that uses a multichannel digital-to-analog (D/A) converter. Fig. 1 shows the experimental setup. The excitation coil generated an oscillating field of 5400 Hz, that magnetized the Resovist MNP sample (500 μg-Fe / 150 μg). The voltage signal from a detection coil contained the third harmonic and fundamental components, that were the effects of the non-linear magnetization of the sample and oscillating field, respectively. The fundamental components were compensated for using a 5400 Hz voltage supply from a multichannel D/A converter and subtracting it with an instrumentation amplifier. The sample was moved in the x–y plane, and the harmonic signal amplified by an operational amplifier was detected at each point. Fig. 2 shows the two-dimensional distribution of the third harmonic signal from the sample at depths of 25 and 50 mm. The image at 50 mm was blurred compared with that at 25 mm because the magnetic flux derived from the oscillating magnetic field coupled to the sample was reduced. The fact that the image was acquired at 50 mm demonstrates the feasibility of MPI using the proposed method. This study was supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI Grant Numbers JP23K20939 and JP20H05652.References: [1] T. Knopp and T. M. Buzug, “Magnetic Particle Imaging—An Introduction to Imaging Principles and Scanner Instrumentation,” Springer, 2012. [2] T. Sasayama, T. Yoshida, and K. Enpuku, “Two-dimensional magnetic nanoparticle imaging using multiple magnetic sensors based on amplitude modulation,” J. Magn. Magn. Mater., vol. 505, Jul. 2020, Art. no. 166765. [3] T. Sasayama, N. Okamura, and T. Yoshida, “Sensitivity improvement of magnetic nanoparticle imaging by compensation with digital-to-analog converter” IEEE Trans. Magn., vol. 57, no. 2, Feb. 2021, Art. no. 5300605.
Magnetic particle imaging (MPI), which displays the concentration distribution of magnetic nanoparticles (MNPs), has gained attention as a new diagnostic imaging technology [1]. One problem with MPI is that it requires a strong gradient field, that causes peripheral nerve stimulation. In this study, the concentration distribution was obtained by arranging the detection coils in an array without a gradient field [2]. The voltage from the detection coil also contained a fundamental component derived from the external magnetic field, that interfered with the measurement. To solve this problem, a single-channel D/A converter and variable resistors were used to compensate for the fundamental component [3]. However, this compensation method is inaccurate. In this study, we propose a new compensation circuit that uses a multichannel digital-to-analog (D/A) converter. Fig. 1 shows the experimental setup. The excitation coil generated an oscillating field of 5400 Hz, that magnetized the Resovist MNP sample (500 μg-Fe / 150 μg). The voltage signal from a detection coil contained the third harmonic and fundamental components, that were the effects of the non-linear magnetization of the sample and oscillating field, respectively. The fundamental components were compensated for using a 5400 Hz voltage supply from a multichannel D/A converter and subtracting it with an instrumentation amplifier. The sample was moved in the x–y plane, and the harmonic signal amplified by an operational amplifier was detected at each point. Fig. 2 shows the two-dimensional distribution of the third harmonic signal from the sample at depths of 25 and 50 mm. The image at 50 mm was blurred compared with that at 25 mm because the magnetic flux derived from the oscillating magnetic field coupled to the sample was reduced. The fact that the image was acquired at 50 mm demonstrates the feasibility of MPI using the proposed method. This study was supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI Grant Numbers JP23K20939 and JP20H05652.References: [1] T. Knopp and T. M. Buzug, “Magnetic Particle Imaging—An Introduction to Imaging Principles and Scanner Instrumentation,” Springer, 2012. [2] T. Sasayama, T. Yoshida, and K. Enpuku, “Two-dimensional magnetic nanoparticle imaging using multiple magnetic sensors based on amplitude modulation,” J. Magn. Magn. Mater., vol. 505, Jul. 2020, Art. no. 166765. [3] T. Sasayama, N. Okamura, and T. Yoshida, “Sensitivity improvement of magnetic nanoparticle imaging by compensation with digital-to-analog converter” IEEE Trans. Magn., vol. 57, no. 2, Feb. 2021, Art. no. 5300605.