Determination of Optical Characteristics of Highly Scattering Biological Medium Based on Enhanced Diffusion Model of Radiation Transport

摘要

The numerical and experimental comparison of two models of laser pulse propagation through highly scattering medium, namely a classical diffusion model and an enhanced diffusion model, is given. It is shown that the results obtained for the two models correspond to experimental data. The enhanced diffusion model more precisely describes the propagation of laser radiation through scattering layers with thickness about the length of mean path of photons.Laser radiation is used in studies of biological media and tissues [1-5].The problem of laser radiation propagation through strongly scattering media (SSM) is very important. Scattering dominates over absorption during laser radiation propagation through biological tissues. Therefore, the model of purely absorbing medium is not appropriate in this case, in contrast to the transmission X-ray tomography algorithm. Laser radiation interaction with SSM includes both scattering and absorption. The equation of radiation transition (ERT) with regard to scattering describes laser radiation propagation through biological tissues. ERT has no analytical solution, so an approximate solution is required. The classical diffusion model (CDM) is presently used [6-8]. In some cases, this model provides an ERT solution, but it has substantial disadvantages limiting the area of its application. The main disadvantage of CDM is substitution of monodirectional radiation source (laser) by an isotropic source embedded in the medium.