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Numerical Simulation of Low-Coherence Radiation Propagation in Turbid Media and Structural Image Reconstruction in Endoscopic Optical Coherence Tomography with Allowance for Speckle Fluctuations

A method of Monte Carlo simulation of low-coherence radiation propagation in turbid media with consideration of speckle noise (the result of mutual interference of secondary spherical waves) is described. The process of photon propagation within investigated object, such as biological tissue, includes the following steps: the photon injection, mean free path determination, the verification of the fulfillment of the boundary condition, the absorption and scattering. Structural image reconstruction in optical coherence tomography (OCT) with consideration of speckle fluctuations is made by summation the statistical weight of the beam coming out of the investigated object inside the detector area with the intensity of a series of pixels of the current A-scan. The key feature of the presented method is the description of the investigated object geometry. Three-dimensional array of voxels combined into parallelograms, and the border cross checking is carried out by using an improved Smith algorithm. The described method can be used to obtain high-quality endoscopic structural OCT images of body cavities and tracts (diagnosis of the respiratory tract, cardiovascular system, gastrointestinal tract, genitourinary system, etc.).