Magnetic resonance imaging (MRI) is one of the most important imaging modalities used in contemporary clinical radiology research and diagnostic practice due to its non-invasive nature, absence of ionizing radiation, high soft tissue contrast, and diverse imaging capabilities. Nevertheless, traditional MRI systems are limited by a relatively low signal-to-noise ratio (SNR), which can be enhanced by increasing the strength of the main magnetic field. Ultra-high field MRI (UHF-MRI) typically refers to MRI systems with a main magnetic field strength of 7 T or higher. The UHF-MRI improves image SNR and extends the boundaries of spatial resolution and detection sensitivity. These advancements not only provide clinicians with richer and more accurate physiological and pathological information but also open new avenues for research on life sciences and cognitive neuroscience.

Currently, the UHF-MRI plays a pivotal role in brain functional and metabolic imaging. In the brain function research, the implementation of high-resolution mesoscale functional imaging techniques has enabled the investigation of laminar-specific neuronal activity within cortical layers, including feedforward and feedback neural information processing pathways. In metabolic studies, the application of hydrogen and multi-nuclear spectroscopy and imaging has yielded more accurate metabolic data, thereby holding substantial promise for advancing our understanding of the pathophysiology underlying functional and metabolic diseases. However, the UHF-MRI is also subject to certain limitations, including issues related to radio-frequency (RF) field in homogeneity, elevated specific absorption ratio (SAR), and susceptibility artifacts.

In this paper, the historical evolution and theoretical underpinnings of UHF-MRI are reviewed, its principal advantages over low-field MRI is elucidated, and the contemporary research on UHF-MRI applications in human brain function and metabolic imaging research are integrated together. Furthermore, the technical limitations associated with UHF-MRI implementation are critically examined and the potential avenues are proposed for the future research direction.