Significance: Near-infrared spectroscopy (NIRS) combined with diffuse correlation spectroscopy (DCS) provides a noninvasive approach for monitoring cerebral blood flow (CBF), oxygenation, and oxygen metabolism. However, these methods are vulnerable to signal contamination from the scalp. Our work evaluated methods of reducing the impact of this contamination using time-resolved (TR) NIRS and multidistance (MD) DCS. Aim: The magnitude of scalp contamination was evaluated by measuring the flow, oxygenation, and metabolic responses to a global hemodynamic challenge. Contamination was assessed by collecting data with and without impeding scalp blood flow. Approach: Experiments involved healthy participants. A pneumatic tourniquet was used to cause scalp ischemia, as confirmed by contrast-enhanced NIRS, and a computerized gas system to generate a hypercapnic challenge. Results: Comparing responses acquired with and without the tourniquet demonstrated that the TR-NIRS technique could reduce scalp contributions in hemodynamic signals up to 4 times (rSD = 3 cm) and 6 times (rSD = 4 cm). Similarly, blood flow responses from the scalp and brain could be separated by analyzing MD DCS data with a multilayer model. Using these techniques, there was no change in metabolism during hypercapnia, as expected, despite large increases in CBF and oxygenation. Conclusion: NIRS/DCS can accurately monitor CBF and metabolism with the appropriate enhancement to depth sensitivity, highlighting the potential of these techniques for neuromonitoring.

中文翻译：

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通过光学测量脑血流量、氧合和代谢直接评估脑外信号污染


意义：近红外光谱 (NIRS) 与漫射相关光谱 (DCS) 相结合，提供了一种监测脑血流量 (CBF)、氧合和氧代谢的无创方法。然而，这些方法很容易受到头皮信号污染的影响。我们的工作评估了使用时间分辨 (TR) NIRS 和多距离 (MD) DCS 减少这种污染影响的方法。目的：通过测量对整体血流动力学挑战的流量、氧合和代谢反应来评估头皮污染的程度。通过收集有或没有阻碍头皮血流的数据来评估污染情况。方法：实验涉及健康参与者。通过对比增强近红外光谱 (NIRS) 证实，使用气动止血带引起头皮缺血，并使用计算机化气体系统产生高碳酸血症挑战。结果：比较使用和不使用止血带获得的反应表明，TR-NIRS 技术可以将血流动力学信号中的头皮贡献减少最多 4 倍（rSD = 3 cm）和 6 倍（rSD = 4 cm）。同样，通过使用多层模型分析 MD DCS 数据，可以分离头皮和大脑的血流反应。使用这些技术，尽管 CBF 和氧合大幅增加，但高碳酸血症期间的新陈代谢没有发生变化，正如预期的那样。结论：NIRS/DCS 可以准确监测 CBF 和代谢，并适当增强深度灵敏度，凸显了这些技术在神经监测方面的潜力。