Low-Field Neuroimaging: Opportunities and Limitations.
Magnetic resonance imaging (MRI) at low magnetic field strengths (under 1 T) has seen renewed interest, driven by technological advances that enhance accessibility, affordability, and versatility. Improvements in design, gradient performance, and artificial intelligence (AI)-assisted reconstruction enable diagnostic-quality neuroimaging at well under 1 T, disrupting the once-peerless dominance of high-field imaging. Modern low-field systems offer advantages in patient comfort, siting flexibility, and/or portability. Reduced infrastructure and safety constraints enable scanning in diverse settings, including outpatient, emergency, and intensive care environments. Lower susceptibility improves imaging near air-bone interfaces, metallic implants, and the skull base, while markedly lowering specific absorption rate (SAR) and acoustic noise. Clinical neurological applications extend across the brain, spine, and skull base and include pediatric or fetal imaging, where improved tolerance and reduced motion artifacts are particularly useful. Lower signal-to-noise ratio (SNR) and limited spatial resolution remain challenges. AI-enhanced reconstruction, optimized pulse sequences, and higher relaxivity of contrast agents help mitigate these drawbacks. Portable low-field MRI also enables point-of-care neuroimaging and intraoperative use, offering real-time insights to expedite diagnosis. However, it is critical to acknowledge that, while low-field applications have found important roles in terms of quality, speed, and performance, higher-field-strength scanners will remain the diagnostic standard for the foreseeable future.