Layer-Specific Functional & Perfusion Imaging of Retina

描述（由申请人提供）： 视网膜约300 μ m厚，代谢非常活跃。由于能量储备有限，它只能依靠持续的氧气和营养供应来维持其功能和结构的完整性。视网膜由两个血液供应，即视网膜和脉络膜循环，滋养内部（即，神经节细胞）和外部（即，光感受器）视网膜。氧进入高度结构化的视网膜细胞层的运输在很大程度上依赖于扩散。因此，在正常条件下，内层和外层视网膜之间的氧张力接近缺氧水平，因此，视网膜非常容易受到缺血性损伤。氧合和灌注缺陷与许多视网膜疾病有关。一种非侵入性的方法来映射视网膜和脉络膜氧合和灌注的变化将是有价值的。非侵入性磁共振成像（MRI）已被广泛用于研究动物和人类的解剖学，生理学和功能。虽然组织氧合和灌注成像是研究大脑功能的常规方法，但由于视网膜薄且靠近充满空气的颅腔，因此将其应用于眼睛在技术上是困难的。我们实验室的最新数据表明，血氧水平依赖（BOLD）功能性MRI可以动态映射视网膜中氧合的视觉诱发变化。该提案的主要目标是：1）开发和验证高分辨率（58x58x1000 mu m3）MRI模式，以映射脉络膜和视网膜的氧合和灌注在视网膜中，和2）通过测量脉络膜与视网膜氧合和灌注的变化，研究视觉诱发的层特异性响应感光细胞与神经节细胞活性的差异激活。将使用4.7特斯拉扫描仪对猫进行研究。

DESCRIPTION (provided by applicant): The retina is approximately 300 mu m thick and is metabolically very active. With limited energy reserve, it depends solely on a continuous supply of oxygen and nutrients to maintain its functional and structural integrity. The retina is nourished by two blood supplies, namely, the retinal and choroidal circulation, that feed the inner (i.e., ganglion cells) and the outer (i.e., photoreceptors) retina, respectively. Oxygen transport into the highly structured retinal cell layers relies heavily on diffusion. As such, the oxygen tension midway between the inner and outer retina is close to hypoxic level under normal conditions and, thus, the retina is very susceptible to ischemic injury. Oxygenation and perfusion deficits have been implicated in numerous retinal diseases. A non-invasive method to map changes in retinal and choroidal oxygenation and perfusion would be valuable. Non-invasive magnetic resonance imaging (MRI) has been widely used for investigating anatomy, physiology and function in both animals and humans. While tissue oxygenation and perfusion imaging is routine for studying brain functions, its application to the eye is technically difficult due to the thin retina and its proximity to the air-filled cranial cavity. Recent data from our lab demonstrate that blood-oxygenation-level-dependent (BOLD) functional MRI can dynamically map visual-evoked changes in oxygenation in the retina. The main goals of this proposal are: 1) to develop and validate high-resolution (58x58x1000 mu m3) MRI modalities to map choroidal and retinal oxygenation and perfusion in the retina, and 2) to investigate the visual-evoked layer-specific responses to differential activations of photoreceptor versus ganglion cell activity by measuring changes in the choroidal versus retinal oxygenation and perfusion. Studies will be performed on cats using a 4.7 Tesla scanner.