【作者】 冯哲；

【导师】 曾绍群；

【作者基本信息】 华中科技大学 ， 生物医学工程， 2005， 硕士

【摘要】 局灶性脑缺血是常见的脑血管疾病之一,致残率和致死率高,研究其病理机制和防治措施具有重大意义。光学成像方法能够实现在体实时监测局灶性脑缺血的动力学过程,其中,基于内源信号的光学成像技术是到目前为止的具有最高的空间分辨率和适用的时间分辨率的在体脑功能成像技术,为研究局灶性脑缺血过程中皮层的功能活动提供了有力的工具; 此外,激光散斑光学成像技术用于测量局部脑皮层血流分布时可获得较高的时间分辨率和空间分辨率,在测量血流上有优势。通过对局灶性脑缺血动力学过程的研究,可以了解脑缺血性损伤的病理生理学机制,对临床诊断、治疗及判断预后等具有重要的指导作用。本文利用内源信号光学成像观测缺血过程中的自发皮层扩散性抑制波,以光信号特征来反映缺血半暗带并监测其动态发展,并应用激光散斑技术实时监测脑缺血及缺血再灌注的血流动力学过程,以研究缺血皮层区域损伤的发展规律及转归。主要研究内容和研究结果如下: (1)采用550 nm内源信号光学成像监测大脑中动脉栓塞局灶性脑缺血模型的血流动力学过程。大脑中动脉栓塞后4小时内,在顶叶皮层观测到一系列自发扩散性抑制波(10.3±4.6次)。前两小时内的扩散性抑制波通常会侵袭整个左侧顶叶皮层,但光信号有明显的区域差异。后两小时内的扩散性抑制波局限于顶叶皮层中央区域,且传播面积逐次减少; 旁侧区域光强基线逐步升高,4小时末,反射光强升高8.4±1.2%。随后TTC染色证明上述旁侧区域已经梗死。实验表明内源信号光学成像技术为确定缺血半暗带并监测其动态发展提供了一种有效方法。(2)使用激光散斑衬比成像技术实时监测大脑中动脉栓塞局灶性脑缺血及再灌注模型的血流动力学过程。观测了缺血30分钟和60分钟脑血流的变化情况,观测到了低灌注、无灌注及过度灌注现象。研究了不同栓塞时间对栓塞后脑血流及再灌注后脑血流的影响。实验结果表明:脑缺血30分钟后,脑血流下降到基值的35±3%,脑缺血60分钟后,脑血流下降到基值的20±3%,解除栓塞后首先出现快速充血过程,持续10～15分钟,充血恢复的灌注量是栓塞前的80±10%,充血过程后低灌注状态维持在基值的60～70%,缺血60～分钟的低灌注水平要比缺血30分钟的低灌注水平低10%。上述实验结果验证了低灌注状态与脑缺血时间相关,缺血时间越长,低灌注水平越低,低更多还原

【Abstract】 Focal cerebral ischemia is one of a common brain blood vessel disease with very high disabled and death ratio. It’s very important to study the pathology mechanism and the prevention and cure method of the disease. Optical imaging method can in vivo examine the dynamic process of focal cerebral ischemia at real time. Thereinto, as a brain functional imaging technique in vivo, the optical imaging based on intrinsic signals (OISI) offers the highest spatial resolution and proper temporal resolution thus far obtained. Moreover, laser speckle contrast imaging (LSCI) shows its advantage on measuring the blood flow with high spatiotemporal resolution. It can be used to investigate the focal cerebral cortical blood flow. By studying the dynamic process of focal cerebral ischemia, we can get to know the pathobiology mechanism of the ischemic damage. It’s instructive for us to make the diagnosis, therapy and prognosis. In this thesis we apply the OISI to examine the spontaneous spreading depression (SD) waves during the focal cerebral ischemia, the character of optical signals are used to reflect the ischemic penumbra and its dynamic development. We apply the LSCI to investigate the dynamic changes of blood flow during ischemic reperfusion of focal cerebral ischemia and post-ischemia hypoperfusion to study the development rule of cortical ischemic region. The overall review and conclusions of the thesis are listed as following: (1) The optical intrinsic signal imaging (OISI) at 550nm was applied to examine the parietal cortex of focal cerebral ischemia rats with the left middle cerebral artery occlusion (MCAO). A series of spontaneous spreading depression (SD) waves (10.3±4.6 times) were observed during the next 4 hours after MCAO. In the earlier 2 hours, the SD waves usually spread across the whole left parietal cortex, however, the optical signals showed significant regional differences. During the later 2 hours, the waves were restricted in the central parietal cortex, and the propagated area decreased reversely with the increasing times of SD waves. The baseline intensity in the lateral area increased steadily, up to 8.4±1.2% at the end of 4 hours. By TTC staining, the lateral area proved to infract focus. The results suggested the optical imaging supplied an effective method to identify the ischemic penumbra and monitor its dynamic evolution. (2) LSCI was applied to investigate the dynamic changes of blood flow during ischemic reperfusion of focal cerebral ischemia and post-ischemia hypoperfusion. The effect of various ischemic duration on post-ischemic and reperfusion cerebral blood flow has been studied. During 60 min MCAO ischemia, perfusion of cerebral blood flow decreased to 20±3% of baseline while perfusion of cerebral blood flow decreased to 35±3% during 30 min MCAO ischemia. After the occlusion was released , there was a brief period(10～15 min)of post-ischemic hyperemia, perfusion recovered to 80±10% and hypoperfusion maintained at low level of 60～70%. The result showed that hypoperfusion in 60 min group was approximately 10% less than that in 30 min group. And the result demonstrated the status of hypoperfusion is dependent on the duration of cerebral ischemia. The longer is the ischemia, the later is the onset of hypoperfusion and the lower of hypoperfusion. Monitoring the dynamic changes of cerebral blood flow help us to understand and investigate the hemodynamic mechanism of hypoperfusion damage after ischemia.更多还原