AI 中文总结
该研究利用OGSE编码在体表征人类大脑随时间变化的径向扩散率，发现短扩散时间和长扩散时间间的径向扩散率变化在皮质脊髓束中值高，对大轴突直径敏感，为神经疾病中神经元微观结构改变研究建立了基线。
AI 中文摘要
扩散时间依赖性，即扩散率和/或扩散峰度随扩散时间的变化，已成为表征组织微观结构特征的有价值的非侵入性成像标记。在白质中，已证实在离体脊髓组织中，径向扩散率（RD，垂直于纤维束的扩散率）在短扩散时间和长扩散时间之间的时间依赖性变化与平均轴突直径密切相关，并能揭示小鼠胼胝体的脱髓鞘情况。尽管这些利用振荡梯度自旋回波（OGSE）在短扩散时间获得的新图像对比度有潜力非侵入性地揭示神经元微观结构以改善神经疾病的评估和靶向治疗，但直到最近才通过高性能梯度MRI系统在人体体内研究中变得可行。在这项初步研究中，我们利用OGSE编码在体表征了人类大脑中随时间变化的RD。短扩散时间和长扩散时间之间的径向扩散率变化（delta_RD）在皮质脊髓束中始终表现出高值，表明delta_RD对人类大脑中较大轴突直径具有高敏感性。在100Hz的高OGSE频率和800s/mm2的中等b值下成像，在皮质脊髓束中产生了最高的delta_RD。本研究为未来神经疾病中神经元微观结构改变的研究建立了基线。
英文摘要
Diffusion time-dependence, defined as variations in diffusivity and/or diffusional kurtosis with diffusion time, has emerged as a valuable non-invasive imaging marker for characterizing tissue microstructural features, such as cell size, density, packing disorder, and membrane permeability. In white matter, diffusion time-dependent changes between the short diffusion time and long diffusion time in radial diffusivity (RD), defined as the diffusivity perpendicular to fiber tracts, were demonstrated to correlate strongly with mean axon diameter in ex vivo spinal cord tissues, and to reveal demyelination in mouse corpus callosum. Despite their potential to non-invasively unveil neuronal microstructures to improve the assessment and targeted therapy of neurological diseases, these novel image contrasts obtained at short diffusion times using oscillating gradient spin echo (OGSE) have only recently become feasible for human in vivo studies with high-performance gradient MRI systems. In this preliminary study, we characterized time-dependent RD with OGSE encoding in the human brain in vivo. The change in radial diffusivity between short diffusion time and long diffusion time (delta_RD) consistently exhibited high values in the corticospinal tract, indicating high sensitivity of delta_RD to large axon diameter in human brains. Imaging at a high OGSE frequency of 100 Hz and a moderate b-value of 800 s/mm2 produced the highest delta_RD in the corticospinal tract. This study established a baseline for future investigations of neuronal microstructural alterations in neurological disorders and diseases.
Comments27 pages, 7 figures, 2 tables
