Monte carlo simulation of signals from model biological tissues measured by an optical coherence tomograph and an optical coherence Doppler tomograph

The results of Monte Carlo simulation of optical coherence tomograph (OCT) signals from layers of a suspension of erythrocytes and an aqueous solution of Intralipid are presented. It is shown that the rear boundary of a layer of an erythrocyte suspension 0.5 mm thick is distinguished in the OCT signal for all the hematocrits considered (5, 10, and 35%). This is explained by fact that the greatest contribution to the signal is made by low-order scattered photons, which ensures good differentiation of internal inclusions and the rear boundary. In the case of the Intralipid solution, the main contribution is made by multiply scattered photons and the signal from the rear boundary is indistinguishable. Signals of an optical coherence Doppler tomograph (OCDT) from a plane-parallel flow of Intralipid between glass plates are also simulated. The effect of the Intralipid concentration on the velocity profile reconstructed from the OCDT signal is studied. It is shown that an increase in the Intralipid concentration leads to a shift in the maximum of the reconstructed velocity profile and to an stretching of the profile. The reason for these distortions is the contribution to the signal from multiple scattering. OCDT signals from a blood layer immersed in an optical phantom of skin are also simulated, and the distortions of the reconstructed profile are analyzed in relation to the depth of the layer.