Time-resolved detection of small objects in turbid media by diffusive light:Simulation versus experiment

A method is presented to simulate the light propagation in turbid media. Based on a numerical algorithm to solve the time-dependent diffusion equation, the method takes into account spatial variations of the reduced scattering and absorption factors of the medium due to the presence of objects as well as random fluctuations of these factors. The simulation results for tissuelike phantoms are compared to experimental data and excellent agreement is found. The technique is employed to explore the possibility of locating millimeter-sized objects, immersed in turbid media, from time-resolved measurements of the transmitted or reflected (near-infrared) light. A method is proposed to enhance the imaging power of the time-resolved technique. Using the dataprocessing technique we find that it is possible to detect 1 mm-diameter objects, independent of their location within the sample and under unfavorable conditions. Experimental data of a time-resolved reflection experiment on a 1mm diameter tube filled with blood and embedded in an intralipid solution are presented. The results show that, using the data processing technique, it is possible to detect the tube to a depth of 15 mm from the illuminated surface in a 70 mm thick sample. Simulation data are in excellent agreement with these experimental results.