Department of Radiology, MGH/MIT/HMS Athinuola A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts, USA.
J Cereb Blood Flow Metab. 2011 Apr;31(4):1051-63. doi: 10.1038/jcbfm.2010.227. Epub 2010 Dec 22.
Measuring cerebral oxygen delivery and metabolism microscopically is important for interpreting macroscopic functional magnetic resonance imaging (fMRI) data and identifying pathological changes associated with stroke, Alzheimer's disease, and brain injury. Here, we present simultaneous, microscopic measurements of cerebral blood flow (CBF) and oxygen partial pressure (pO(2)) in cortical microvessels of anesthetized rats under baseline conditions and during somatosensory stimulation. Using a custom-built imaging system, we measured CBF with Fourier-domain optical coherence tomography (OCT), and vascular pO(2) with confocal phosphorescence lifetime microscopy. Cerebral blood flow and pO(2) measurements displayed heterogeneity over distances irresolvable with fMRI and positron emission tomography. Baseline measurements indicate O(2) extraction from pial arterioles and homogeneity of ascending venule pO(2) despite large variation in microvessel flows. Oxygen extraction is linearly related to flow in ascending venules, suggesting that flow in ascending venules closely matches oxygen demand of the drained territory. Oxygen partial pressure and relative CBF transients during somatosensory stimulation further indicate arteriolar O(2) extraction and suggest that arterioles contribute to the fMRI blood oxygen level dependent response. Understanding O(2) supply on a microscopic level will yield better insight into brain function and the underlying mechanisms of various neuropathologies.
从微观层面上测量脑氧输送和代谢对于解释宏观功能磁共振成像 (fMRI) 数据以及识别与中风、阿尔茨海默病和脑损伤相关的病理变化非常重要。在这里，我们在麻醉大鼠的皮层微血管中同时进行了微观测量，以获得基线条件下和体感刺激期间的脑血流 (CBF) 和氧分压 (pO(2))。我们使用定制的成像系统，使用傅里叶域光相干断层扫描 (OCT) 测量 CBF，并使用共焦磷光寿命显微镜测量血管 pO(2)。CBF 和 pO(2) 的测量值在距离上表现出不均匀性，这是 fMRI 和正电子发射断层扫描无法解决的。基线测量表明，尽管微血管流量存在很大差异，但从软脑膜小动脉中提取 O(2)，并且上升静脉的 pO(2)均匀。氧提取与上升静脉中的流量呈线性相关，表明上升静脉中的流量与引流区域的氧气需求密切匹配。体感刺激期间的氧分压和相对 CBF 瞬变进一步表明小动脉中的 O(2)提取，并表明小动脉有助于 fMRI 血氧水平依赖反应。从微观层面上了解氧供应将更好地了解大脑功能和各种神经病理学的潜在机制。
