Measurement of Blood Flow Velocity in Cerebral Microvessels by a Fiber-Optic Laser-Doppler Anemometer Microscope

本研究项目旨在建立我们研制的光纤激光多普勒风速显微镜（FLDAM）在测量脑脊膜微血管内红细胞速度的适用性，并分析颅内压升高时的血流动力学。在大鼠顶骨区一侧植入封闭的颅窗，观察颅底微循环。用FLDAM成功地测量了直径为10 ~ 230 μ m的单头微血管中的红细胞流速。小动脉内红细胞流速随心跳同步有规律脉动，幅度可达平均流速的46%，而小静脉内红细胞流速仅呈小幅度随机波动。速度脉动幅度定义为总体平均速度最大值与最小值之差的一半。小动脉的时间平均流速随着直径的增加而增加。直径为10 mm和50 mm的小动脉平均流速分别为3.5和14 mm/s。小动脉流速相对于股动脉压力的滞后时间随着沿血管从上游到下游距离的增加而增加，表明血流脉冲沿小动脉传播。测定了数条动脉的血流脉冲传播速度。速度在10到115厘米/秒之间。通过改变封闭颅窗植入大鼠的内压，研究颅内压对颅底微循环的影响。当ICP从0 ~ 50 mmHg升高时，小静脉的平均直径从1.1单调下降到0.78，其中直径由ICP=5mmHg时的直径归一化。另一方面，小静脉的时间平均流速从0.85单调增加到1.91。结果表明，小静脉的体积流速随ICP变化不明显。与小静脉相比，ICP对小动脉的影响较小。在一定的ICP值（ICP_<cr'>）下，随血管位置的不同，小动脉流速脉动幅度随ICP逐渐增大。ICP_<cr>随血管直径增大而增大，沿小动脉由上游向下游递减，说明ICP_<cr>代表了小动脉脉动某一阶段的血管内压力。少

This research project was aimed to establish the applicability of our developed fiber-optic laser-Doppler anemometer microscope (FLDAM) to the measurement of red cell velocity in the cerebral pial microvessels and was also aimed to analyze the blood flow dynamics under the increased intracranial pressures.A closed cranial window was implanted on one side of the parietal region of rats to observe the brain pial microcirculation. The red cell velocity in single pial microvessels with diameter range from 10 to 230 mum was successfully measured by the FLDAM.The red cell velocity in arterioles showed regular pulsation synchronous with the heart beats with amplitude up to 46 % of the mean velocity, while the velocity in venules only showed random fluctuations with small amplitude. The amplitude of velocity pulsation was defined as the half of the difference betweenthe maximum and minimum of the ensemble average velocity. The temporal mean velocity in the arterioles increased with increasing … More diameter. It was 3.5 and 14 mm/s for the arteriole with 10 and 50 mum in diameter, respectively, on an average. The time lag of the velocity in the arteriole relative to the femoral arterial pressure increased with the distance along the vessel from upstream to downstream, which indicates the propagation of flow pulse along the arteriole. The propagation velocity of flow pulse was determined for several pial arterioles. It ranged between 10 and 115 cm/s.Effects of intracranial pressure (ICP) on the pial microcirculation were studied by changing the internal pressure of the closed cranial window implanted in the rats. The average diameter of venules decreased monotonically from 1.1 to 0.78 as the ICP increased from 0 to 50 mmHg, where the diameter is normalized by the diameter at ICP=5mmHg. On the other hand, the temporal mean velocity in venules increased monotonically from 0.85 to 1.91. As a result, the volume flow rate in venules did not change significantly with ICP.The changes of arterioles with ICP were small compared with those of venules. The amplitude of velocity pulsation in arterioles showed stepwise increase with ICP at a certain value of ICP,ICP_<cr'> which depended on the location of the vessel. ICP_<cr> increased with increasing vessel diameter and decreased from upstream to downstream along an arteriole, suggesting that ICP_<cr> represents the intravascular pressure of the arteriole at a certain phase of pulsation. Less