Red blood cells (RBCs) transport oxygen to tissues and remove carbon dioxide. Diffuse optical flowmetry (DOF) assesses deep tissue RBC dynamics by measuring coherent fluctuations of multiply scattered near-infrared light intensity. While classical DOF measurements empirically correlate with blood flow, they remain far-removed from light scattering physics and difficult to interpret in layered media. To advance DOF measurements closer to the physics, here we introduce an interferometric technique, surmounting challenges of bulk motion to apply it in awake humans. We reveal two measurement dimensions: optical phase, and time-of-flight (TOF), the latter with 22 picosecond resolution. With this multidimensional data, we directly confirm the unordered, or Brownian, nature of optically probed RBC dynamics typically assumed in classical DOF. We illustrate how incorrect absorption assumptions, anisotropic RBC scattering, and layered tissues may confound classical DOF. By comparison, our direct method enables accurate and comprehensive assessment of blood flow dynamics in humans.

中文翻译：

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飞行时间解决的光场波动揭示了深层人体组织生理学。

红细胞 (RBC) 将氧气输送到组织并清除二氧化碳。漫射光流计 (DOF) 通过测量多重散射近红外光强度的相干波动来评估深部组织 RBC 动力学。虽然经典 DOF 测量在经验上与血流相关，但它们与光散射物理学相距甚远，并且难以在分层介质中解释。为了使 DOF 测量更接近物理，我们在这里引入了一种干涉测量技术，克服了体运动的挑战，将其应用于清醒的人类。我们揭示了两个测量维度：光学相位和飞行时间 (TOF)，后者具有 22 皮秒分辨率。通过这些多维数据，我们直接确认了经典 DOF 中通常假设的光学探测 RBC 动力学的无序或布朗性质。我们说明了不正确的吸收假设、各向异性 RBC 散射和分层组织如何混淆经典 DOF。相比之下，我们的直接方法能够准确、全面地评估人体血流动力学。