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

Motion correction for phase-resolved dynamic optical coherence tomography imaging of rodent cerebral cortex

Cardiac and respiratory motions in animals are the primary source of image quality degradation in dynamic imaging studies, especially when using phase-resolved imaging modalities such as spectral-domain optical coherence tomography (SD-OCT), whose phase signal is very sensitive to movements of the sample. This study demonstrates a method with which to compensate for motion artifacts in dynamic SD-OCT imaging of the rodent cerebral cortex. We observed that respiratory and cardiac motions mainly caused, respectively, bulk image shifts (BISs) and global phase fluctuations (GPFs). A cross-correlation maximization-based shift correction algorithm was effective in suppressing BISs, while GPFs were significantly reduced by removing axial and lateral global phase variations. In addition, a non-origin-centered GPF correction algorithm was examined. Several combinations of these algorithms were tested to find an optimized approach that improved image stability from 0.5 to 0.8 in terms of the cross-correlation over 4 s of dynamic imaging, and reduced phase noise by two orders of magnitude in ~8% voxels.K99 NS067050 - NINDS NIH HHS; R01EB000790 - NIBIB NIH HHS; R01 EB001954 - NIBIB NIH HHS; R01 EB001954-09 - NIBIB NIH HHS; P01NS055104 - NINDS NIH HHS; R01 NS057476 - NINDS NIH HHS; K99NS067050 - NINDS NIH HHS; R01 EB000790 - NIBIB NIH HHS; R01-EB001954 - NIBIB NIH HHS; R01NS057476 - NINDS NIH HHS; P01 NS055104 - NINDS NIH HHS; P41 EB015896 - NIBIB NIH HHSPublished versio

Evaluation of periphyton quantity on different natural substrates in Earthen lined pond

Experiments were conducted in outdoor earthen lined pond to study periphyton quantity on three types of natural substrates such as split bamboo pole, coconut coir and coconut shell, which was placed inside the earthen lined pond filled with seawater for duration of 45 days. Observations were made in every 15th day for growth of periphyton both qualitatively and quantitatively on the three natural substrates and physico-chemical properties of selected pond water such as transparency, water temperature, salinity, pH, Dissolved oxygen, Ammonia (NH3-N), Nitrite (NO2-N), Nitrate (NO3-N), BOD and Chlorophyll ‘a’ were recorded during periphyton samplings. The periphy-ton quantity (34562 ± 671 cells / cm2) observed for coconut coir was higher than the split bamboo pole (33104 ± 810 cells / cm2), and coconut shell (21194 ± 872 cells / cm2) in the final day of the experiment. One way ANOVA of the data collected clearly affirmed that significant differences were observed (P < 0.05) in periphyton quantity among the three substrates tested. A total 16 phyto-periphytic microalgae (Bacillariophyceae – 10 types, Dinophyceae – 4 types and Cyanophyceae – 2 types) and 10 Zoo-periphyton (Copepod- 4 types, Meroplankton – 4 types and Tintin-nidae – 2 types) were recorded from these three substrates. Among the different phyto-periphytic microalgae, Bacil-lariophyceae group were found to be more (Split bamboo pole – 72%, Coconut coir – 73% and Coconut shell – 71%) on three substrates studied. Further, coconut coir was found to be best substrate than split bamboo pole and coconut shell, which can be utilized by fin and shellfishes as natural food