Exponential Attenuation of Light Along Nonlinear Path Through the Biological Model

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Although exhibiting some transparency when illuminated with red or near infrared light(e.g. Jöbsis, 1977; Hazeki and Tamura 1988), biological tissues are intensely light scattering within this range. As a result, the optical pathlength through the tissue is significantly different from the spacing between the points incidented and transmitted. Beer-Lambert law that stands for clear solution can’t be simply applied to the tissue and various devices for the correction are done. Then two analytical approaches to the study of optical propagation in blood are investigated: a multiple scattering theory (Twersky, 1970) and a diffusion theory (Zdrojkowski and Pisharoty, 1970). We have studied the way that the spectroscopic data can be quantitatively treated by discriminating temporally and spatially the passage of an instantaneous light pulse through the tissue. In this report, assumption that light intensity along the non linear path taken by photons through the living tissue is exponentially attenuated has been tested in model system. Light path taken by photons is important for time resolved spectroscopy. The application to tissue has been performed by several investigators (e.g. Martin et al., 1980; Tamura et al., 1987; Chance et al., 1988).