chapter  18
Near-Infrared Fluorescence Imaging and Spectroscopy in Random Media and Tissues
ByE.M. Sevick-Muraca, E. Kuwana, A. Godavarty, J.P. Houston, A.B. Thompson, and R. Roy
Pages 66

Most radiation-based spectroscopic and imaging techniques are typically dependent upon evaluating a nonscattered or singly scattered signal for retrieval of quantitative information. For example, absorption spectroscopy depends upon the survival of unscattered light across a known path length, L; dynamic light scattering or photon correlation spectroscopy requires the uctuation of light intensity owing to its scatter by Brownian motion out of the optical path; x-ray and computed x-ray tomography depend upon the straight-line path of nonabsorbed x-rays, and so forth. Yet most systems of interest multiply scatter radiation of low energy and, in particular, require diluted suspensions or nonscattering media when dealing with optical interrogation. Hence, optical techniques developed for imaging and spectroscopy are usually plagued by the inuence of scatter. In order to expand the quantitative applicability of optical techniques to these real systems, new techniques have been developed that focus on coherence properties, temporal and spatial correlation, and other properties in order to extract the nonscattered or singly scattered light from a multiply scattered signal. Yet these approaches neglect the largest portion of the signal, the scattered signal, in favor of that portion that possesses the smallest signal to noise ratio (SNR).