Liu Bingxue, Shah Shashwat, Küreli Gülce, Devor Anna, Boas David A, Cheng Xiaojun
Neurophotonics Center, Boston University, Boston, Massachusetts 02215, USA.
Department of Electrical and Computer Engineering, Boston University, Boston, Massachusetts 02215, USA.
Biomed Opt Express. 2023 Aug 21;14(9):4790-4799. doi: 10.1364/BOE.497604. eCollection 2023 Sep 1.
Laser speckle contrast imaging (LSCI) measures 2D maps of cerebral blood flow (CBF) in small animal brains such as mice. The contrast measured in LSCI also includes the static and slow-varying components that contain information about brain tissue dynamics. But these components are less studied as compared to the fast dynamics of CBF. In traditional wide-field LSCI, the contrast measured in the tissue is largely contaminated by neighboring blood vessels, which reduces the sensitivity to these static and slow components. Our goal is to enhance the sensitivity of the contrast to static and slow tissue dynamics and test models to quantify the characteristics of these components. To achieve this, we have developed a short-separation speckle contrast optical spectroscopy (ss-SCOS) system by implementing point illumination and point detection using multi-mode fiber arrays to enhance the static and slow components in speckle contrast measurements as compared to traditional wide-field LSCI (WF-LSCI). We observed larger fractions of the static and slow components when measured in the tissue using ss-SCOS than in traditional LSCI for the same animal and region of interest. We have also established models to obtain the fractions of the static and slow components and quantify the decorrelation time constants of the intensity auto-correlation function for both fast blood flow and slower tissue dynamics. Using ss-SCOS, we demonstrate the variations of fast and slow brain dynamics in animals before and post-stroke, as well as within an hour post-euthanasia. This technique establishes the foundation to measure brain tissue dynamics other than CBF, such as intracellular motility.
激光散斑对比成像（LSCI）可测量小鼠等小动物大脑中的二维脑血流（CBF）图。LSCI中测量的对比度还包括包含脑组织动力学信息的静态和缓慢变化成分。但与CBF的快速动力学相比，这些成分的研究较少。在传统的宽场LSCI中，组织中测量的对比度在很大程度上受到相邻血管的污染，这降低了对这些静态和缓慢成分的敏感性。我们的目标是提高对静态和缓慢组织动力学对比度的敏感性，并测试模型以量化这些成分的特征。为了实现这一目标，我们开发了一种短距离散斑对比光谱学（ss-SCOS）系统，通过使用多模光纤阵列实现点照明和点检测，以增强散斑对比测量中的静态和缓慢成分，与传统的宽场LSCI（WF-LSCI）相比。对于同一动物和感兴趣区域，我们观察到使用ss-SCOS在组织中测量时，静态和缓慢成分的比例比传统LSCI中的更大。我们还建立了模型来获得静态和缓慢成分的比例，并量化快速血流和较慢组织动力学的强度自相关函数的去相关时间常数。使用ss-SCOS，我们展示了中风前后以及安乐死后一小时内动物快速和缓慢脑动力学的变化。这项技术为测量除CBF之外的脑组织动力学，如细胞内运动性，奠定了基础。
