Zaharchuk G, Mandeville J B, Bogdanov A A, Weissleder R, Rosen B R, Marota J J
Harvard-MIT Division of Health Sciences and Technology, Harvard Medical School, Boston, Massachusetts, USA.
Stroke. 1999 Oct;30(10):2197-204; discussion 2204-5. doi: 10.1161/01.str.30.10.2197.
To determine how cerebral blood flow (CBF), total and microvascular cerebral blood volume (CBV), and blood oxygenation level-dependent (BOLD) contrast change during autoregulation and hypotension using hemodynamic MRI.
Using arterial spin labeling and steady-state susceptibility contrast, we measured CBF and changes in both total and microvascular CBV during hemorrhagic hypotension in the rat (n=9).
We observed CBF autoregulation for mean arterial blood pressure (MABP) between 50 and 140 mm Hg, at which average CBF was 1.27+/-0.44 mL. g(-1). min(-1) (mean+/-SD). During autoregulation, total and microvascular CBV changes were small and not significantly different from CBF changes. Consistent with this, no significant BOLD changes were observed. For MABP between 10 and 40 mm Hg, total CBV in the striatum increased slightly (+7+/-12%, P<0.05) whereas microvascular CBV decreased (-15+/-17%, P<0.01); on the cortical surface, total CBV increases were larger (+21+/-18%, P<0.01) and microvascular CBV was unchanged (3+/-22%, P>0.05). With severe hypotension, both total and microvascular CBV decreased significantly. Over the entire range of graded global hypoperfusion, there were increases in the CBV/CBF ratio.
Parenchymal CBV changes are smaller than those of previous reports but are consistent with the small arteriolar fraction of total blood volume. Such measurements allow a framework for understanding effective compensatory vasodilation during autoregulation and volume-flow relationships during hypoperfusion.
利用血流动力学磁共振成像确定在自动调节和低血压过程中脑血流量（CBF）、脑血容量总量及微血管脑血容量（CBV）以及血氧水平依赖（BOLD）对比如何变化。
使用动脉自旋标记和稳态磁化率对比，我们测量了大鼠（n = 9）出血性低血压期间的CBF以及脑血容量总量和微血管CBV的变化。
我们观察到平均动脉血压（MABP）在50至140 mmHg之间时存在CBF自动调节，此时平均CBF为1.27±0.44 mL·g⁻¹·min⁻¹（均值±标准差）。在自动调节期间，脑血容量总量及微血管CBV变化较小，且与CBF变化无显著差异。与此一致，未观察到明显的BOLD变化。对于MABP在10至40 mmHg之间时，纹状体中的脑血容量总量略有增加（+7±12%，P<0.05），而微血管CBV减少（-15±17%，P<0.01）；在皮质表面，脑血容量总量增加更大（+21±18%，P<0.01），微血管CBV无变化（3±22%，P>0.05）。在严重低血压时，脑血容量总量及微血管CBV均显著下降。在分级全身性灌注不足的整个范围内，CBV/CBF比值增加。
实质CBV变化比先前报告的小，但与总血容量中小动脉部分一致。此类测量为理解自动调节期间有效的代偿性血管舒张以及灌注不足期间的容量 - 流量关系提供了一个框架。
