Dual-slope method for enhanced depth sensitivity in frequency-domain near-infrared spectroscopy

项目总结 在这个生物工程研究项目中，我们提出了一种新的频域近距离成像技术。 红外光谱(FD-NIRS)，旨在非侵入性地实现对深部组织的选择性敏感性 漫反射光谱分析和成像。一种对深层组织具有更强敏感性的技术 相对于浅表组织可对非侵入性光学诊断和监测产生广泛影响 在脑血氧仪和脑功能成像中尤为重要。建议的技术基于 相位双斜率(这是在FD-NIR中测量的调制光信号的相位)的新概念， 其至少需要两个光源和两个光学探测器放置在组织上 有特别安排。除了实现对更深层次组织的选择性敏感性外，相位双斜率还 对乐器漂移和运动伪像(钉子除外)的敏感度很低，这是非常理想的特性 用于强健的测量。首先，我们将使用扩散理论和蒙特卡罗模拟来识别 源/探测器的几何布置和强度调制频率可优化 相双斜率适用于各种非均质层状介质。二是实施优化阶段 用商用FD-NIRS仪器演示双斜率条件下对组织样治疗的有效性 体模，我们将设计基于摩尔-彭罗斯的特殊源-探测器阵列进行成像 相位双斜率测量中雅可比矩阵的伪逆。第三，我们将设计和建设一个 专用紧凑型、可穿戴、无光纤且经济实惠的FD-NIR设备，可进一步扩展 相位双斜率法适用于日常条件下自由运动的受试者，以及适用于点 护理应用程序。第四，我们将进行人体研究以进行技术性能测试(在骨骼肌中 在血管闭塞期间)，并展示了相位双斜率方法在功能性 大脑成像(在认知激活时在前额叶皮质)。特别是，后一项研究将阐明 相对血流量/血容量对皮质血流动力学的贡献，并将允许双重任务 行走时完成认知任务的受试者的测量结果。该项目的总体目标是 通过开发特殊技术来推进生物组织的漫反射光学测量领域 收集和分析FD-NIR数据，以提高非红外光谱数据的质量、可靠性和信息含量 侵入性近红外光谱在研究和临床中的应用。

PROJECT SUMMARY In this Bioengineering Research project, we propose to develop a novel technique for frequency-domain near- infrared spectroscopy (FD-NIRS) that aims to achieve selective sensitivity to deeper tissue in non-invasive diffuse optical spectroscopy and imaging. A technique that features a stronger sensitivity to deeper tissue relative to superficial tissue can have a broad impact on non-invasive optical diagnostics and monitoring and is especially important in cerebral oximetry and functional brain imaging. The proposed technique is based on the new concept of phase dual-slopes (this is the phase of the modulated optical signal measured in FD-NIRS), which requires a minimum of two light sources and two optical detectors placed on the tissue according to a special arrangement. In addition to achieving selective sensitivity to deeper tissue, phase dual slopes are weakly sensitive to instrumental drifts and motion artifacts (except spikes), which is a highly desirable property for robust measurements. First, we will use diffusion theory and Monte Carlo simulations to identify source/detector geometrical arrangements and intensity modulation frequencies that optimize performance of the phase dual-slope for a variety of heterogeneous layered media. Second, we will implement optimal phase dual-slope conditions with a commercial FD-NIRS instrument to demonstrate effectiveness on tissue-like phantoms, and we will design special source-detector arrays for imaging based on the Moore-Penrose pseudoinverse of the Jacobian matrix for phase dual-slope measurements. Third, we will design and build a dedicated compact, wearable, fiber-less, and cost-effective FD-NIRS device for further broadening the applicability of the phase dual-slope method to freely moving subjects in everyday conditions, and for point-of- care applications. Fourth, we will perform human studies for technical performance tests (in skeletal muscle during vascular occlusions) and to demonstrate the effectiveness of the phase dual-slope method for functional brain imaging (in the prefrontal cortex during cognitive activation). In particular, the latter study will elucidate the relative blood flow/blood volume contributions to cortical hemodynamics and will allow for dual-task measurements in subjects performing cognitive tasks while walking. The broad objective of this project is to advance the field of diffuse optical measurements of biological tissue by developing special techniques for collection and analysis of FD-NIRS data to enhance the quality, reliability, and information content of non- invasive NIRS in research and clinical applications.