An Exploration of A Phased-array RF Coil for Very-low Field Brain MRI

Very-low magnetic field (VLF) magnetic resonance imaging (MRI) presents an affordable and easily deployable solution, facilitating MRI usage within inpatient wards, intensive care units (ICU), ambulances, and resource-limited areas. Despite the advantages, VLF MRI encounters challenges like a reduced signal-to-noise ratio (SNR). While high field MRI have employed phased-array RF coils to enhance SNR and expedite imaging, leveraging phased-array RF coil to improve imaging SNR and reduce scan time in VLF MRI has been highly expected. Compared to high field MRI, the dramatically reduced working frequency has a significant impact on the performance of the phased-array RF coil for VLF MRI. In this study, we attempted to evaluate the performance of phased-array RF coils for VLF MRI. Specifically, we built a phased-array RF coil system, which consists of an optimized 8-channel head RF coil, and a custom-made low input impedance (LII) preamplifier. We optimized the system based on impedance analysis and evaluate its performance by bench test, phantom imaging and healthy volunteer imaging. This paper presents the first attempt to develop phased-array RF coil for VLF MRI, and revealed the advantage of improving SNR by RF coil structure optimization and the challenge of phased-array decoupling in VLF MRI.