Conventional diffusion imaging uses pulsed gradient spin echo (PGSE) waveforms with diffusion times of tens of milliseconds (ms) to infer differences of white matter microstructure. The combined use of these long diffusion times with short diffusion times (<10 ms) enabled by oscillating gradient spin echo (OGSE) waveforms can enable more sensitivity to changes of restrictive boundaries on the scale of white matter microstructure (e.g. membranes reflecting the axon diameters). Here, PGSE and OGSE images were acquired at 4.7 T from 20 healthy volunteers aged 20-73 years (10 males). Mean, radial, and axial diffusivity, as well as fractional anisotropy were calculated in the genu, body and splenium of the corpus callosum (CC). Monte Carlo simulations were also conducted to examine the relationship of intra- and extra-axonal radial diffusivity with diffusion time over a range of axon diameters and distributions. The results showed elevated diffusivities with OGSE relative to PGSE in the genu and splenium (but not the body) in both males and females, but the OGSE-PGSE difference was greater in the genu for males. Females showed positive correlations OGSE-PGSE diffusivity difference with age across the CC, whereas there were no such age correlations in males. Simulations of radial diffusion demonstrated that for axon sizes in human brain both OGSE and PGSE diffusivities were dominated by extra-axonal water, but the OGSE-PGSE difference nonetheless increased with area-weighted outer-axon diameter. Therefore, the lack of OGSE-PGSE difference in the body is not entirely consistent with literature that suggests it is composed predominantly of axons with large diameter. The greater OGSE-PGSE difference in the genu of males could reflect larger axon diameters than females. The OGSE-PGSE difference correlation with age in females could reflect loss of smaller axons at older ages. The use of OGSE with short diffusion times to sample the microstructural scale of restriction implies regional differences of axon diameters along the corpus callosum with preliminary results suggesting a dependence on age and sex.

中文翻译：

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沿着人类胼胝体的扩散时间依赖性以及通过振荡梯度自旋回波扩散张量成像评估的年龄和性别差异的探索

传统的扩散成像使用具有数十毫秒 (ms) 扩散时间的脉冲梯度自旋回波 (PGSE) 波形来推断白质微结构的差异。通过振荡梯度自旋回波 (OGSE) 波形将这些长扩散时间与短扩散时间 (<10 ms) 结合使用，可以使对白质微结构尺度上限制性边界的变化更加敏感（例如，反映轴突直径的膜）。在这里，PGSE 和 OGSE 图像是从 20 名 20-73 岁的健康志愿者（10 名男性）以 4.7 T 获得的。计算了胼胝体 (CC) 的膝部、体部和脾脏的平均、径向和轴向扩散率以及各向异性分数。还进行了蒙特卡罗模拟，以检查轴突内和轴突外径向扩散率与扩散时间在一系列轴突直径和分布范围内的关系。结果表明，OGSE 相对于 PGSE 在男性和女性的膝部和脾脏（但不是身体）中的扩散率升高，但 OGSE-PGSE 差异在男性的膝部中更大。女性在整个 CC 中显示出 OGSE-PGSE 扩散率差异与年龄呈正相关，而男性则没有这种年龄相关性。径向扩散的模拟表明，对于人脑中的轴突大小，OGSE 和 PGSE 扩散率均受轴突外水的支配，但 OGSE-PGSE 差异仍然随着面积加权的外轴突直径而增加。所以，体内缺乏 OGSE-PGSE 差异与文献并不完全一致，文献表明它主要由大直径轴突组成。雄性属中较大的 OGSE-PGSE 差异可能反映了比雌性更大的轴突直径。OGSE-PGSE 与女性年龄的差异相关性可以反映年龄较大时较小轴突的丢失。使用具有短扩散时间的 OGSE 对限制的微观结构尺度进行采样意味着沿着胼胝体的轴突直径存在区域差异，初步结果表明对年龄和性别的依赖。OGSE-PGSE 与女性年龄的差异相关性可以反映年龄较大时较小轴突的丢失。使用具有短扩散时间的 OGSE 对限制的微观结构尺度进行采样意味着沿胼胝体的轴突直径存在区域差异，初步结果表明依赖于年龄和性别。OGSE-PGSE 与女性年龄的差异相关性可以反映年龄较大时较小轴突的丢失。使用具有短扩散时间的 OGSE 对限制的微观结构尺度进行采样意味着沿胼胝体的轴突直径存在区域差异，初步结果表明依赖于年龄和性别。