Improving penetration depth and spatial resolution for in vivo deep imaging of mouse brain using 2200 nm Optical Coherence Microscopy

摘要： 皮质下病理是衰老、阿尔茨海默病和血管性痴呆的共同特征，但一直以来 在体内以微米分辨率进行研究具有挑战性。光学方法，如双光子显微镜，成像 浅层皮质在微米级，但这些传统的显微镜方法的分辨率下降 成像深度迅速超过600微米。标准的全脑磁共振成像(MRI)方法 还不能提供蜂窝级别的分辨率，而且价格昂贵。因此，迫切需要各种方法来 在微观层面评估深层皮质和皮质下的血流灌注和细胞损伤，从而弥合差距 在现有的表面光学显微镜和宏观成像之间。这项提案将制定、验证、 并展示了用于皮质下结构纵向成像的先进光学显微镜方法 用2200 nm光学相干显微镜观察小鼠脑。2200 nm成像，其中组织散射是 分别与1300 nm和1700 nm相比降低2.5x和1.5x，将增强 弹道(而不是多次散射)光子到焦点，并提高光子的比例 在没有进一步散射的情况下被检测到的焦点的反向散射。这两个好处都将 大幅提高成像时的信号定位、空间分辨率和信背景比 在大脑深处。这些方法将进一步深入到活着的小鼠大脑中，成像 皮质下结构(即海马体和齿状回)和病理学的分辨率高于 以前都是可能的。

Abstract: Subcortical pathology is a common feature in aging, Alzheimer's disease and vascular dementia but has been challenging to study with micron resolution in vivo. Optical methods such as two-photon microscopy image the superficial cortex at the micron-scale, but the resolution of these conventional microscopic methods degrades rapidly beyond 600 microns imaging depth. Standard whole-brain magnetic resonance imaging (MRI) methods do not yet provide cellular-level resolution and are expensive. Thus, there is a pressing need for methods to assess deep cortical and subcortical perfusion and cellular injury at the microscopic level, thus bridging the gap between existing superficial optical microscopy and macroscopic imaging. This proposal will develop, validate, and demonstrate advanced optical microscopy methods for longitudinal imaging of subcortical structures in the mouse brain using 2200 nm Optical Coherence Microscopy. 2200 nm imaging, in which tissue scattering is reduced by 2.5× and 1.5× compared to 1300 nm and 1700 nm, respectively, will enhance the delivery of ballistic (as opposed to multiply-scattered) photons to the focal spot, and enhance the proportion of photons backscattered from the focus that are detected without further scattering. Both of these benefits will substantially improve the signal localization, spatial resolution and signal-to background ratio when imaging deep in the brain. These methods will push penetration depths further into the living mouse brain, imaging subcortical structures (i.e. hippocampal proper and dentate gyrus) and pathology at higher resolutions than were previously possible.