International Journal on Magnetic Particle Imaging IJMPI
Vol. 10 No. 1 Suppl 1 (2024): Int J Mag Part Imag

Proceedings Articles

Towards an MPI-MRI-MEG fused neuroimaging system
Acquisition of MR images at 300 kHz with a newly developed compact OPM

Main Article Content

Tetsuo Kobayashi (Kyoto University)


Optically pumped magnetometer (OPM) is a promising magnetic sensor alternative to SQUID that enables the measurement of very small magnetic signals. In addition, OPMs have the intrinsic advantage of not requiring cryogenic cooling. We have been developing a compact and portable OPM module with a pump-probe arrangement. Since sensitivity of OPM does not depend on frequency, it is suitable to be used as a receiving sensor for magnetic particle imaging (MPI) and ultra-low-field (ULF) MRI systems. In a previous study, we demonstrated the possibility of remotely detecting magnetic fields generated from super-paramagnetic iron oxide nanoparticles using an OPM with a flux transformer [1].  Here, we introduce our newly developed miniaturized OPM module having its noise floor less than 20 fT/Hz1/2 as well as the first magnetic shieldless OPM-based ULF-MRI scanner with an OPM operating at a Larmor frequency of 300 kHz.

Article Details


[1] T. Oida, K. Kato, Y. Ito and T. Kobayashi: “Remote detection of magnetic signals with a compact atomic magnetometer for use in MRI-MPI hybrid systems”, Inter. J. on Magnetic Particle Imaging, vol. 5, no.1, Article ID 1906001, 7 pages, 2019.
[2] Y. Mamishin, Y. Ito and T. Kobayashi, “A novel method to accomplish simultaneous multilocation magnetic field measurements based on pump beam modulation of an atomic magnetometer”, IEEE Trans. on Magnetics, vol. 53, no. 5, pp. 1-6, 2017.
[3] K. Nishi, Y. Ito and T. Kobayashi, “Development of a high-sensitivity multi-channel probe beam detector towards MEG measurements of small animals with an optically pumped K-Rb hybrid atomic magnetometer”, Optics Express, vol. 26, no. 2, pp. 1988-1996, 2018.
[4] I. Hilschenz, H. Natsukawa, Y. Ito, T. Oida, T. Yamamoto and T. Kobayashi, “Remote detected low-field MRI using an optically pumped atomic magnetometer combined with a liquid cooled pre-polarization coil”, Journal of Magnetic Resonance, vol. 274, pp. 89-94, 2017.
[5] S. Hori, T. Oida, T. Moriya. A. Saito, M. Suyama, and T. Kobayashi, “Magnetic shieldless ultra-low-field MRI with an optically pumped magnetometer,” Journal of Magnetic Resonance, vol. 343, 107280, 2022.
[6] N. Kato, M. Yamada, K. Otani, Y. Ito, and T. Kobayashi, “Development of an optically pumped magnetometer module for biomagnetic measurements (in Japanese),” Bulletin of Topical Symposium of the Magnetics Society of Japan, vol. 234, pp. 13-17, 2021.
[7] Y. Ito, M. Ueno and T. Kobayashi, “Neural magnetic field dependent fMRI toward direct functional connectivity measurements: A phantom study”, Scientific Reports, vol.10, 5463, 2020.