Microscale Oxygenation Mapping During Stroke

项目总结 缺血性卒中后脑损伤的程度是一个时间和空间依赖的函数 缺氧的症状。尽管已经对缺血损伤的氧阈值进行了研究 多年来，局部血氧水平与神经元结构变化之间的详细关系 而在体内研究功能一直是极具挑战性的。树突刺是特别有趣的。 因为它们可能在脑损伤后皮质可塑性中起关键作用，并可能成为 康复训练策略。然而，氧水平在单个树枝晶水平上的作用是 人们对此知之甚少，这在很大程度上是因为缺乏能够用微米来量化氧合的方法 三维比例分辨率。尽管氧气敏感电极能够实现精确的氧气 在单一位置进行测量，其侵袭性使其无法进行慢性研究和 绘制氧气分布图。氧敏磷光染料的最新进展 在啮齿动物模型中结合多光子技术为无创氧映射提供了新的可能性 激动人心。尽管这种方法有可能对微血管氧合产生新的见解，但Low 信号水平限制了氧合测量的速度和渗透深度。因此， 本项目的目标是开发一种改进的成像方法，用于三维测量 血管内和血管外氧合水平与树突形态成像同时进行 使用这个系统来量化局部氧气水平和树突重塑之间的关系 在脑缺血后。氧气测绘的技术进步将涉及两个方面 组件。首先，我们将通过以下方式提高氧敏探测器的磷光信号电平 开发一种空间多路复用再生放大器激励源，将产生几个 在空间上偏移激发点。空间分辨率的最小折衷将被 在时间分辨率和成像深度方面有相当大的提高。第二，我们将提炼一种方法来 使用微泡辅助聚焦超声瞬时破坏血脑屏障，这将 允许将染料输送到血管外空间。这些进步加在一起将使慢性 以微米级分辨率测量氧气水平。然后我们将使用这些工具来量化 体表动脉和穿透小动脉的纵向氧梯度及引流 在基础状态下和闭塞单个小动脉后形成小静脉。最后，我们将量化 单个树突周围的氧水平与这些树突形态变化的关系 急性和慢性缺血时的树突。

PROJECT SUMMARY The extent of brain injury following ischemic stroke is a time and space dependent function of the degree of oxygen deprivation. Although oxygen thresholds for ischemic damage have been investigated for many years, the detailed relationship between local oxygen levels and alterations in neuronal structure and function has been extremely challenging to study in vivo. Dendritic spines are of particular interest since they likely play a key role in cortical plasticity following brain injury and are a potential target for rehabilitative training strategies. However, the role of oxygen levels at the level of single dendrites is poorly understood, in large part due to a lack of methods capable of quantifying oxygenation with micron scale resolution in three dimensions. Although oxygen sensitive electrodes enable precise oxygen measurement at a single location, their invasive nature precludes them from chronic studies and for mapping oxygen distributions. Recent advances in oxygen sensitive phosphorescent dyes have opened up new possibilities for noninvasive oxygen mapping in rodent models when combined with multiphoton excitation. Despite the potential for this approach to yield new insight into microvascular oxygenation, low signals levels limit the speed and penetration depth of the oxygenation measurements. Therefore, the goal of this project is to develop an improved imaging method for three-dimensional determination of intra- and extra-vascular oxygenation levels simultaneously with imaging of dendritic morphology and to use this system to quantify the relationship between local oxygen levels and dendritic remodeling following cerebral ischemia. The technological advances in oxygen mapping will involve two components. First, we will improve the phosphorescence signal levels of the oxygen sensitive probe by developing a spatially multiplexed regenerative amplifier excitation source that will produce several spatially offset excitation spots. The minimal tradeoff in spatial resolution will be offset by the considerable gain in temporal resolution and imaging depth. Second, we will refine a method to transiently disrupt the blood brain barrier using microbubble-assisted focused ultrasound, which will permit delivery of the dye to the extravascular space. Together these advances will enable chronic measurement of oxygen levels with micron scale resolution. We will then use these tools to quantify the longitudinal oxygen gradients from surface and penetrating arterioles through capillaries and draining venules under baseline conditions and after occlusion of a single arteriole. Finally, we will quantify the relationship between oxygen levels surrounding individual dendrites and morphological changes in these dendrites during both acute and chronic ischemia.