Ultrasonic-tagged remote interferometric flowmetry for brain activity

对大脑活动的光学监测本质上与各种操作优势相关， 包括低成本和便携的无创床边连续监测能力。而普雷瓦- Lent光学大脑监测方法是基于测量血氧水平依赖(BOLD) 来自血液吸收的信号，光学方法测量来自装饰的脑血流量(CBF)- 当相干光被血流散射时，可能会提供一种有希望的替代方案。CBF 测量对大脑具有更高的敏感性，并与大胆的信号相辅相成。他们的组合- 国家可以提供更精确的神经活动图景，例如，可以用来计算 大脑中新陈代谢的摄氧率。无创性脑血流量测量也有助于 脑血管健康、认知老化和神经素的人脑功能神经成像- 紧张性护理。然而，目前的光学CBF检测方法，如扩散相关规范- 透视镜(DCS)、基于激光散斑的成像及其变种容易受到脑外污染。 国家。根据光子路径的分布，它们在深度敏感度上是有限的。对于这款R21 项目，我们建议开发和评估一种新的脑血流量测量方法，称为超声- 标记远程干涉流量计(URIF)，用于高灵敏度和选择性脑活动的任务- 性价比监测。URIF与当前的光学CBF方法有很大的不同。鉴于当前的光学 CBF方法测量来自所有光路的积分信号，其中信号光子具有 通过大脑活动部位的被没有信号的光子淹没，乌里夫·瑟- 通过超声标记和外差检测，只选择并相干放大信号光子。 提顿。更重要的是，通过一种新颖的理论和实验框架，URIF可以量化局部 在深度达到一厘米及以上的毫米大小的大脑活动部位的CBF，移除前- 并显著提高深度敏感度、选择性和空间分辨率。 与血流动力学相关的局部吸收变化也可以同时监测。我们 首先提出用单次离轴全息术发展URIF，然后进行数值模拟和实验。 在人脑模型上对乌里夫进行计数验证。URIF用于深度测量的性能指标 流量将根据准确性、灵敏度和选择性来确定。如果成功，这项技术将 为远程脑活动流量测量铺平了一条新的道路，并填补了现有的重要测量空白 光学和非光学方法一直无法解决。

Optical monitoring of brain activities is intrinsically associated with various operational advantages, including low-cost and portable noninvasive bedside continuous monitoring capabilities. While the preva- lent optical brain monitoring methods are based on measuring blood oxygenation level-dependent (BOLD) signals from blood absorption, optical methods measuring cerebral blood flow (CBF) from the decor- relation of coherent light when scattered by the blood flow may provide a promising alternative. CBF measurement has higher sensitivity to the brain and is complementary to BOLD signals. Their combi- nation can provide a more precise picture of neural activity and may be, for example, used to compute the metabolic oxygen uptake rate in the brain. Noninvasive CBF measurement is also instrumental for functional neuroimaging of the human brain for cerebrovascular health, cognitive aging, and neuroin- tensive care. However, the current optical CBF detection methods, such as diffusion correlation spec- troscopy (DCS), laser speckle-based imaging, and their variants, are prone to extracerebral contami- nation. They are limited in depth sensitivity relying on the distribution of the photon paths. For this R21 project, we propose to develop and evaluate a novel CBF measurement method, known as ultrasonic- tagged remote interferometric flowmetry (URIF), for the task of high sensitivity and selectivity brain activ- ity monitoring. URIF is substantially different from current optical CBF methods. Whereas current optical CBF methods measure an integrated signal from all optical paths in which the signal photons that have passed through the brain activity site are overwhelmed by non-signal photons that have not, URIF se- lects and coherently amplifies only the signal photons through ultrasonic tagging and heterodyne detec- tion. More importantly, with a novel theoretical and experimental framework, URIF can quantify the local CBF at the millimeter-size brain activity site at depths reaching one centimeter and beyond, removing ex- tracerebral contamination and significantly enhancing depth sensitivity, selectivity, and spatial resolution. Local absorption variation associated with hemodynamics can also be monitored simultaneously. We propose first to develop URIF using single-shot off-axis holography and then numerically and experimen- tally validate URIF on human brain phantoms. The performance metrics of URIF for measuring deep flow will be determined in terms of accuracy, sensitivity, and selectivity. If successful, the technology will pave a novel avenue for remote flowmetry of brain activity and fill a vital measurement gap that existing optical and non-optical methods have not been able to address.