A simulation study on receivers of ultra-low field MRI with an optically pumped magnetometer

Abstract

Recently, ultra-low-field MRI (ULF-MRI) has attracted attention due to its potential of downsizing and low cost. The ULF-MRI has low resonance frequency and narrow bandwidth, so the receiving system should be selected with consideration of the frequency response. To clarify the performances of two different receivers: optically pumped magnetometer (OPM) combined with a flux transformer and conventional induction coil system, we created an MRI simulator and implemented the transfer function of two different receiving systems. The structural similarity with the original image (SSIM) and the signal-to-noise ratio (SNR) were as evaluation indices of the reconstructed images. In the evaluation based on reconstructed images, the OPM system had higher SNR than the induction coil in the frequency range less than several 100 kHz. It was also found that the OPM system has a high SNR even with a small number of coil turns.