Direct Detection of Magnetic Resonance Signals in Ultra-Low Field MRI Using Optically Pumped Atomic Magnetometer With Ferrite Shields: Magnetic Field Analysis and Simulation Studies

An ultra-low field (ULF) magnetic resonance imaging (MRI) system with an optically pumped atomic magnetometer (OPAM) has recently been proposed. However, to measure MR signals with high sensitivity in ULF-MRI systems with OPAMs, the resonant frequencies of a sample and an OPAM must be matched. In this study, we propose a direct detection method of the MR signals using ferrite shields. In addition, the magnetic field distribution analyses and MR signal intensity simulations were performed to improve the sensitivity of direct MR signal detection by using an OPAM with ferrite shields. The magnetic field distribution analyses and MR signal intensity simulations indicated that the MR signals could be detected by the proposed method and that the ferrite shields with high relative permeability improved the sensitivity of direct MR signal detection.