Determination of the optical properties of turbid media from a single Monte Carlo simulation

Abstract. We describe a fast, accurate method for determination of the optical coefficients of ‘semi-infinite ’ and ‘infinite ’ turbid media. For the particular case of time-resolved reflectance from a biological medium, we show that a single Monte Carlo simulation can be used to fit the data and to derive the absorption and reduced scattering coefficients. Tests with independent Monte Carlo simulations showed that the errors in the deduced absorption and reduced scattering coefficients are smaller than 1 % and 2%, respectively. Knowledge of the optical properties of biological tissue is important for many applications of light in medicine. Derivation of the absorption and scattering coefficients from a set of measurements requires a theoretical model. The transport equation (Ishimaru 1978) can be used to describe light propagation in tissue, but because this equation can only be solved numerically for most cases of interest, the diffusion approximation (Ishimaru 1978, Patterson et al 1991) is often applied. Solutions of the diffusion equation for simple geometries can be readily obtained (Patterson et al 1989, Moulton 1990, Haskell et al 1994) but the diffusion approximation breaks down near a radiation source (Kienle et al 1996, Hielscher et al 1995). This region is of special interest in applications such as endoscopy and coheren