Multiple scattering in optical coherence tomography signal: Monte Carlo modeling and experimental study

The angle biased Monte Carlo technique is applied to simulate the OCT signal from homogeneous turbid medium. The OCT signal is divided into two categories: one is from a specific imaging target layer in the turbid medium; the other is from the other background medium. The Class II signal has wider spatial and angular distribution than the Class I signal. And it experiences more scattering events. The multiple scattered photons will decrease the contrast of the OCT image and their contributions become dominant at larger depths. The average number of scattering events increases with the probing depth for both Class I and II lights. Experimental study is conducted by measuring the depth-resolved degree of polarization (DOP) of the back- scattered signal from the turbid media. The DOP is derived form the Stokes vector measurements. The incident light is linear polarized and could be depolarize by the multiple scattering. The DOP decreases to 0.5 when Class I signal is equal to the Class II signal. Experiments in the intralipid solution with different scattering coefficient show the imaging depth is limited to 3-4 optical depths