STATISTICAL BASIS FOR THE DETERMINATION OF OPTICAL PATHLENGTH IN TISSUE

In this paper we show how to derive the mean and variance of the trans illuminated signal obtained in models of light propagation in tissue, based both on a stochastic Monte Carlo method and on a deterministic d iffusion approximation. The theoretical treatment of the Monte Carlo m odel applies only to integrated intensity measurements, whereas the di ffusion approximation gives an estimator for the time-dependent case a s well. We present results that show the accurate prediction of Monte Carlo statistics, and propose that the diffusion approximation is ther efore a suitable mechanism for incorporating noise into modelling proc edures.