Flow Properties of Heterogeneous Turbid Media Probed by Diffusing Temporal Correlation

Abstract

Variations in the amplitude and phase of diffuse photon density waves is known to yield important information about the structural properties of turbid media, such as the scattering and absorption coefficients. Information on the dynamical properties of turbid media may be obtained from the temporal fluctuations of light fields emanating from the media. In this contribution, we demonstrate that variations in temporal correlation functions of the temporal intensity fluctuations of different speckles of light can be used to derive information about the spatially varying dynamical properties of turbid media. We first present a diffusion for the temporal correlation function for systems where the dynamics are governed by Brownian motion and shear and random flow. We demonstrate the validity of the correlation diffusion for heterogeneous systems by comparing the theoretical results with experimental results for systems governed by different dynamical processes, e.g. flow. As an illustration of the usefulness of this correlation technique to biomedical optics, we discuss the application of this technique to diagnosing the thickness of burned tissue. The correlation diffusion is an important, unique tool for analyzing the complex dynamical signals that arise from heterogeneous biological systems.