ABSTRACT Technology will be developed to enable future compact, mid-field (0.7 Tesla) magnetic resonance imaging (MRI) systems, for improving human health worldwide. MRI is an indispensable imaging tool that provides measurement capabilities unavailable with other modalities. Yet, due to its expense, large size, and demand on facility infrastructure, high quality MRI remains inaccessible to a large fraction of the world’s population, particularly in remote and resource-limited settings. The existence of portable, affordable, high-performing MRI technology will substantially expand its accessibility for both clinical care and neuroimaging research. Although low field (<0.1 Tesla) MRI scanners are now commercially available, to date they have not produced images of similar quality as those of mid- and high-field MRI scanners unless relying on intensive post-processing based on machine-learning and AI, which makes the reliability of these low field images uncertain at this time. As an alternative approach for increasing portability, and thus increasing access to mid-field MRI (0.1 - 1 Tesla), in this project we will further develop new technology called FREE (Frequency-modulated Rabi-Encoded Echoes) that has potential to eliminate one of the most expensive and massive hardware components of an MRI system; namely, the pulsed field gradients that are conventionally used to encode spatial information in MRI. Instead, the MR signals will be encoded by spatially varying radiofrequency (RF) fields, using specialized multi-channel RF coils and a novel frequency-swept pulse technique that performs spatial encoding using RF field gradients, even when the magnet produces a highly nonuniform field. Further, this project will build upon the previous innovations by this same team in a U01 grant that led to: 1) the capability to perform MRI with extreme magnetic field inhomogeneity (~2-3 orders of magnitude greater than what is commonly perceived to be necessary), 2) a unique compact high temperature superconducting (HTS) head-only magnet, and 3) a state-of-the-art multi-channel digital spectrometer for programming and controlling the MRI scanner. The research in this R56 project will involve computer simulations and experimental tests using the HTS head-only MRI scanner operating at 0.7 Tesla. We will develop a multichannel RF coil and multi-echo 2D-FREE imaging with parallel RF transmission and reception. Products will include new MRI methods, software, and hardware to achieve highly portable midfield MRI. Future portable mid-field MRI scanners based on this new technology will help people in remote, resource-limited settings to address health inequities.

Narrative Magnetic resonance imaging (MRI) has evolved into an indispensable tool in clinical medicine and biomedical research. Yet, due to its high cost to purchase, site, and maintain, access to MRI is limited to mainly well-funded medical centers or research institutions. This project will test a new silent MRI technology that simplifies the MRI system in terms of its hardware components, cost, size, weight, and infrastructure requirements. Future portable MRI scanners based on this technology have a chance of empowering communities in remote, resource-limited settings to address health inequities, build local capacity for better health, improve understanding of brain development and degeneration in diverse populations, and enable access to high quality clinical care worldwide.