Experimental studies of time-resolved light propagation in turbid media

Abstract

<p>The purpose of the work presented here is to determine whether time-resolved remittance spectroscopy can be used to determine noninvasively the optical properties of turbid media such as biological tissue. Knowledge of these properties is important in both therapeutic and diagnostic applications of light in medicine. In all experiments, the propagation of light was modelled as a diffusive process. The thesis consists of three interrelated sections. In the first section, the optical properties of tissue-simulating liquid phantoms were determined using established techniques based on steady-state diffusion theory and Monte Carlo simulations. In the second section, time-resolved experiments were performed in homogeneous liquid phantoms of varying geometries, and the ability of a simple time-dependent diffusion model to predict the remitted (transmitted or reflected) pulse shape and hence the optical properties of the phantoms was determined. In the final section, time-resolved studies were conducted in a homogeneous brain-simulating phantom containing discrete absorbing or scattering objects. Picosecond laser pulses were incident on the inhomogeneous phantom and the remitted pulses were compared to model pulses derived from a finite difference representation of the time-dependent diffusion equation.</p>