Ultra-Low-Field Brain MRI for Point-of-Care Applications: A Technology Review

Magnetic resonance imaging (MRI) is a cornerstone of neurological care, serving as the gold standard for diagnosing pathologies, such as brain tumors and, together with computed tomography, stroke. However, the high capital costs, specialized infrastructure requirements such as expensive and bulky radiofrequency-shielding cages, and the operational complexity of conventional high-field scanners (1.5T and 3T) largely confine MRI to centralized imaging facilities. This scenario often leads to reliance on brain computed tomography or ultrasound in point-of-care settings, despite MRI's superior soft-tissue contrast for diagnosis and prognosis. In the past decade, there has been renewed interest in compact and simplified ultra-low-field (under 0.1T) MRI scanners, fueled by advances in engineering and computing. Here, we review the recent developments in ultra-low-field brain MRI, which enable imaging in open environments and demonstrate initial clinical applicability in point-of-care settings. We also envision future developments along 3 focus areas (ie, hardware, imaging protocols, and data-driven image formation and analysis) to address the current limitations of image quality and contrast in ultra-low-field brain MRI systems.