There has been a long-standing demand for noninvasive neuroimaging methods that can detect neuronal activity at both high temporal and high spatial resolution. We present a two-dimensional fast line-scan approach that enables direct imaging of neuronal activity with millisecond precision while retaining the high spatial resolution of magnetic resonance imaging (MRI). This approach was demonstrated through in vivo mouse brain imaging at 9.4 tesla during electrical whisker-pad stimulation. In vivo spike recording and optogenetics confirmed the high correlation of the observed MRI signal with neural activity. It also captured the sequential and laminar-specific propagation of neuronal activity along the thalamocortical pathway. This high-resolution, direct imaging of neuronal activity will open up new avenues in brain science by providing a deeper understanding of the brain’s functional organization, including the temporospatial dynamics of neural networks.

Myelin water imaging (MWI) is an MRI imaging biomarker for myelin. This method can generate an in vivo whole‐brain myelin water fraction map in approximately 10 minutes. It has been applied in various applications including neurodegenerative disease, neurodevelopmental, and neuroplasticity studies. In this review we start with a brief introduction of myelin biology and discuss the contributions of myelin in conventional MRI contrasts. Then the MRI properties of myelin water and four different MWI methods, which are categorized as T2‐, T2*‐, T1‐, and steady‐state‐based MWI, are summarized. After that, we cover more practical issues such as availability, interpretation, and validation of these methods. To illustrate the utility of MWI as a clinical research tool, MWI studies for two diseases, multiple sclerosis and neuromyelitis optica, are introduced. Additional topics about imaging myelin in gray matter and non‐MWI methods for myelin imaging are also included. Although technical and physiological limitations exist, MWI is a potent surrogate biomarker of myelin that carries valuable and useful information of myelin.Evidence Level: 5Technical Efficacy: 1J. MAGN. RESON. IMAGING 2021;53:360‐373.

In this study, the effect of the electric potential of lipid vesicle surfaces on MR relaxation times and magnetization transfer was investigated. Negatively charged multilamellar vesicles were formed, and their surface potential was adjusted by changing the sodium ion concentration. While the zeta potential changed from -57.0 mV to –21.6 mV, T2 increased from 48.2 ms to 67.4 ms, PSR decreased from 5.5% to 5.0%, kmf decreased from 82.7 Hz to 40.6 Hz, and T2b increased from 177.8 μs to 189.1 μs. These observations are expected to be utilized to image action potential generated in white matter.

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