Simultaneous, noninvasive observation of elastic scattering, fluorescence and inelastic scattering as a monitor of blood flow and hematocrit in human fingertip capillary beds

We report simultaneous observation of elastic scattering, fluorescence, and inelastic scattering from in vivo near-infrared probing of human skin. Careful con- trol of the mechanical force needed to obtain reliable reg- istration of in vivo tissue with an appropriate optical sys- tem allows reproducible observation of blood flow in capillary beds of human volar side fingertips. The time dependence of the elastically scattered light is highly cor- related with that of the combined fluorescence and Raman scattered light. We interpret this in terms of turbidity the impeding effect of red blood cells on optical propagation to and from the scattering centers and the changes in the volume percentages of the tissues in the irradiated volume with normal homeostatic processes. By fitting to a model, these measurements may be used to determine volume fractions of plasma and RBCs. © 2009 Society of Photo-Optical