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Understanding Deep Human Tissue Physiology from Light Field Fluctuations Resolved by Time-of-Flight

By 11th February 2020No Comments

The following study was conducted by Scientists from University of California Davis, USA. Study is published in Nature Communications Journal as detailed below.

Nature Communications (2020); Volume:11, Article number: 391

Time-of-flight Resolved Light Field Fluctuations Reveal Deep Human Tissue Physiology


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.


Nature Communications



Kholiqov, O., Zhou, W., Zhang, T. et al. Time-of-flight resolved light field fluctuations reveal deep human tissue physiology. Nat Commun 11, 391 (2020).