Application ofq-Space Diffusion MRI for the Visualization of White Matter

Abstract

White matter abnormalities in the CNS have been reported recently in various neurological and psychiatric disorders. Quantitation of nonGaussianity for water diffusion by q-space diffusional MRI (QSI) renders biological diffusion barriers such as myelin sheaths; however, the time-consuming nature of this method hinders its clinical application. In the current study, we aimed to refine QSI protocols to enable their clinical application and to visualize myelin signals in a clinical setting. For this purpose, animal studies were first performed to optimize the acquisition protocol of a non-Gaussian QSI metric. The heat map of standardized kurtosis values derived from optimal QSI (myelin map) was then created. Histological validation of the myelin map was performed in myelin-deficient mice and in a nonhuman primate by monitoring its variation during demyelination and remyelination after chemical spinal cord injury. The results demonstrated that it was sensitive enough to depict dysmyelination, demyelination, and remyelination in animal models. Finally, its utility in clinical practice was assessed by a pilot clinical study in a selected group of patients with multiple sclerosis (MS). The human myelin map could be obtained within 10 min with a 3 T MR scanner. Use of the myelin map was practical for visualizing white matter and it sensitively detected reappearance of myelin signals after demyelination, possibly reflecting remyelination in MS patients. Our results together suggest that the myelin map, a kurtosis-related heat map obtainable with time-saving QSI, may be a novel and clinically useful means of visualizing myelin in the human CNS.

Applications of induced pluripotent stem cell technologies in spinal cord injury

“…Recently, we established a novel technique for visualizing white matter area by q ‐space diffusional magnetic resonance imaging, and named it ‘myelin mapping’ (Fujiyoshi et al . ). Myelin maps depict de‐ and remyelination status in animal models and patients with multiple sclerosis.…”

Worldwide initiatives to advance brain research

“…Hideyuki Okano’s lab at RIKEN/Keio University has been working on high-resolution structural and diffusion imaging of the marmoset brain 8,9 and has also developed an eight-channel phased array coil to record visually evoked functional blood-oxygen-level dependent (BOLD) responses in awake animals. Efforts from Noritaka Ichinohe’s lab at RIKEN to develop methods for tracer injection and from Tetsuro Yamamori’s group to study the prefrontal cortex are being integrated with the macroscopic MRI-based brain model.…”

Neuroscience Research Using Non-human Primate Models and Genome Editing

“…Magnetic resonance imaging (MRI) is a non-invasive imaging technique to visualize various organs in detail. We have adapted a number of MRI techniques, including diffusion tensor tractography (DTT; Fujiyoshi et al 2007;Hikishima et al 2015) and voxel based morphometric (VBM) analysis (Hikishima et al , 2015, and a new method for the visualization of myelin (Myelin Map; Fujiyoshi et al 2016). …”