Data from: Microstructure and cerebral blood flow within white matter of the human brain: a TBSS analysis

Background: White matter (WM) fibers connect different brain regions and are critical for proper brain function. However, little is known about the cerebral blood flow in WM and its relation to WM microstructure. Recent improvements in measuring cerebral blood flow (CBF) by means of arterial spin labeling (ASL) suggest that the signal in white matter may be detected. Its implications for physiology needs to be extensively explored. For this purpose, CBF and its relation to anisotropic diffusion was analyzed across subjects on a voxel-wise basis with tract-based spatial statistics (TBSS) and also across white matter tracts within subjects. Methods: Diffusion tensor imaging and ASL were acquired in 43 healthy subjects (mean age = 26.3 years). Results: CBF in WM was observed to correlate positively with fractional anisotropy across subjects in parts of the splenium of corpus callosum, the right posterior thalamic radiation (including the optic radiation), the forceps major, the right inferior fronto-occipital fasciculus, the right inferior longitudinal fasciculus and the right superior longitudinal fasciculus. Furthermore, radial diffusivity correlated negatively with CBF across subjects in similar regions. Moreover, CBF and FA correlated positively across white matter tracts within subjects. Conclusion: The currently observed findings on a macroscopic level might reflect the metabolic demand of white matter on a microscopic level involving myelination processes or axonal function. However, the exact underlying physiological mechanism of this relationship needs further evaluation.

研究背景：白质（white matter, WM）纤维连接不同脑区，对维持大脑正常功能至关重要。但目前学界对白质内脑血流量及其与白质微结构的关联尚缺乏深入认知。近年来，借助动脉自旋标记（arterial spin labeling, ASL）技术测量脑血流量（cerebral blood flow, CBF）的方法取得进展，提示可检测到白质内的相关信号，但其生理学意义仍有待广泛探索。为此，本研究采用基于纤维束的空间统计（tract-based spatial statistics, TBSS）方法，在体素层面分析了43名健康受试者的脑血流量及其各向异性弥散的相关性，并在受试者个体内的白质纤维束层面开展了关联分析。
研究方法：对43名健康受试者（平均年龄26.3岁）采集弥散张量成像（diffusion tensor imaging, DTI）及动脉自旋标记数据。
研究结果：跨受试者分析显示，在胼胝体压部、右侧丘脑后辐射（含视辐射）、胼胝体大钳、右侧额枕下束、右侧下纵束及右侧上纵束等脑区，白质内脑血流量与各向异性分数（fractional anisotropy, FA）呈正相关；同时，在类似脑区，径向弥散率与脑血流量呈负相关。此外，在受试者个体内的白质纤维束层面，脑血流量与各向异性分数同样呈正相关。
研究结论：本研究在宏观层面观测到的上述关联，可能反映了微观层面白质的代谢需求，涉及髓鞘形成过程或轴突功能。但该关联的确切潜在生理学机制仍有待进一步研究验证。