Continuous and Longitudinal Monitoring of Cerebral Blood Flow and Metabolism in Freely Moving Rodents

摘要 测定脑血流量（CBF）和脑氧代谢率（CMRO 2）， 对大脑活动的反应允许研究潜在的兴奋性和抑制性神经反应， 优化神经系统疾病和脑血管疾病新疗法的关键。啮齿动物（小鼠 世纪以来，动物（包括老鼠）一直在帮助科学家研究人类疾病， 今天使用的动物模型。这些啮齿类动物模型的主要局限性是脑血流动力学不稳定。 主要在麻醉的动物中和在有限的时间点测量。然而，麻醉会影响大脑 血液动力学影响深远，并干扰行为健康、认知功能和睡眠障碍的研究。 在清醒的啮齿类动物中，可用于脑血流动力学监测的少数方法需要侵入性开颅术 通过在大脑上安装各种光电极/超声波探头， 测量过程中的身体在NIH（R21）的支持下，我们最近开发了一种创新的，非侵入性的， 低成本、无纤维、近红外漫射散斑对比血流计（DSCF）探头，固定在头部 用于连续监测CBF。本提案的目的是 扩展、优化和验证这种新技术，使其成为双波长、多通道、漫射散斑 对比血流血氧测定（DSCFO）系统，用于同时进行CBF、脑氧合和 CMRO 2在有意识、自由移动的啮齿动物中。DSCFO使用小型近红外激光二极管， 波长作为点光源，微型CMOS相机作为2D检测器阵列来检测空间动态光 通过红细胞的固有运动的散射（即，CBF）和氧合和脱氧血红蛋白的光衰减 [HbO 2]和[Hb]）。CBF、[HbO 2]和[Hb]的组合使得能够基于 建立模型。2D相机阵列能够在两个半球上进行大脑反应的2D映射 在啮齿动物头部的不同深度。重要的是，DSCFO探头和控制单元之间的连接 都是电线/电缆（即，无纤维），从而提供了连续脑监测的承诺， 自由移动的主题。利用模拟头模对DSCFO系统进行了标定和优化， 根据既定技术在麻醉啮齿动物中进行验证，我们将评估其性能， 在有或无缺血性脑损伤的清醒、自由活动啮齿动物中进行连续和纵向脑监测 中风侮辱。当我们在这个项目中探索中风引起的大脑结果时，DSCFO技术 适用于研究其他神经系统疾病和脑血管疾病。结合我们 正在进行的R21在人类受试者中的研究，在啮齿动物中完成这项研究将产生独特的非侵入性， 一种快速、低成本、多尺度和多模式的脑映射工具，用于神经科学研究和临床 应用.最终，CBF、[HbO 2]、[Hb]和CMRO 2的水平/变化和组合可作为 用于评估脑健康和脑病理状况和干预的结果的生物标志物。

ABSTRACT Measurements of cerebral blood flow (CBF) and cerebral metabolic rate of oxygen consumption (CMRO2) in response to brain activity allows investigation of underlying excitatory and inhibitory neural responses and holds the key to optimizing novel therapies for neurological disorders and cerebrovascular diseases. Rodents (mice and rats) have been helping scientists investigate human diseases for well over a century and still make up 95% of the animal models used today. Major limitations with these rodent models are that cerebral hemodynamics is measured mostly in anesthetized animals and at limited time points. However, anesthesia impacts cerebral hemodynamics profoundly and interferes with studies of behavioral health, cognitive function, and sleep disorder. A few methods available for cerebral hemodynamic monitoring in conscious rodents require invasive craniotomy with installation of various opto-electrode/ultrasound probes onto the brain, which restrains animal’s head or body during measurements. Supported by NIH (R21), we have recently developed an innovative, noninvasive, low-cost, fiber-free, near-infrared diffuse speckle contrast flowmetry (DSCF) probe, which affixes on the heads of anesthetized rodents and awake humans for continuous monitoring of CBF. The goal of this proposal is to extend, optimize, and validate this novel technology toward a dual-wavelength, multi-channel, diffuse speckle contrast flow-oximetry (DSCFO) system for simultaneous regional mapping of CBF, cerebral oxygenation, and CMRO2 in conscious, freely moving rodents. DSCFO uses small near-infrared laser diodes at different wavelengths as point sources and a tiny CMOS camera as a 2D detector array to detect spatial dynamic light scattering by intrinsic motions of red blood cells (i.e., CBF) and light attenuations by oxy- and deoxy- hemoglobin absorptions ([HbO2] and [Hb]). Combination of CBF, [HbO2], and [Hb] enables derivation of CMRO2 based on established models. The 2D camera array enables 2D mapping of cerebral responses over two hemispheres and at different depths of the rodent head. Importantly, connections between the DSCFO probe and control unit are all electrical wires/cables (i.e., fiber-free), thereby offering the promise for continuous cerebral monitoring in freely moving subjects. After calibrating and optimizing the DSCFO system using head-simulating phantoms and validation in anesthetized rodents against established techniques, we will evaluate its performance for continuous and longitudinal cerebral monitoring in conscious, freely moving rodents with or without ischemic stroke insult. While we explore stroke-induced cerebral outcomes in this project, the DSCFO technology is applicable for studying other neurological disorders and cerebrovascular diseases. In combination with our ongoing R21 studies in human subjects, completion of this study in rodents will generate a unique noninvasive, fast, low-cost, multiscale, and multimodal brain mapping tool for both neuroscience research and clinical applications. Ultimately, the levels/variations and combination of CBF, [HbO2], [Hb], and CMRO2 may serve as biomarkers for assessing brain health and outcomes of cerebral pathological conditions and interventions.