Detection of tiny oscillatory magnetic fields using low-field MRI: A combined phantom and simulation study

• Published in: Journal of magnetic resonance (1997) 2020-10, Vol.319, p.106828-106828, Article 106828
• Main Authors: Ueda, Hiroyuki, Ito, Yosuke, Oida, Takenori, Taniguchi, Yo, Kobayashi, Tetsuo
• Format: Article
• Language: English
• Subjects: Bloch equation; Low-field fMRI; Spin-locked Mz; Stimulus-induced rotary saturation
• ISSN: 1090-7807; 1096-0856
• DOI: 10.1016/j.jmr.2020.106828

[Display omitted] •Comparison of two spin-lock methods for low-field functional MRI.•The analytical solution of the Bloch equation under these sequences.•The difference of the methods was clarified experimentally and theoretically.•With 0.3-T MRI scanner, we investigated the detectable strength of the two methods. We demonstrated the feasibility of the spin-lock preparation sequence using low-field magnetic resonance (MR) imaging that prevents interference from blood-oxygenation-level-dependent effects. We focused on two spin-lock preparations: spin-lock Mz (SL-Mz) and stimulus-induced rotary saturation (SIRS) and analyzed the magnetization dynamics during the sequences using the Bloch equation. Next, we performed phantom experiments using a loop coil to investigate the MR signal change as a function of the target signal strength and phase. Furthermore, we performed curve fittings to consider the radio frequency, which agreed with the experimental results. Then, we investigated the detectable strength of the magnetic field, and the SL-Mz detected a signal strength of 2.34 nT. In conclusion, our experimental results showed good agreement with the results obtained using the Bloch equation.