Modeling the optical coherence tomography geometry using the extended Huygens-Fresnel principle and Monte Carlo simulations

We have developed a new theoretical description of the optical coherence tomography (OCT) geometry for imaging in highly scattering tissue. The new model is based on the extended Huygens-Fresnel principle, and it is valid in the single and multiple scattering regimes. The so-called shower curtain effect, which manifests itself in standard OCT systems, is an inherent property of the extended Huygens-Fresnel model. We compare the theoretical analysis with experiments carried out on samples consisting of aqueous suspensions of microspheres and solid phantoms. We calculate the signal-to-noise ratio, and provide an estimation of the maximum attainable probing depth for shot-noise limited detection. Furthermore, we investigate the focusing of the Gaussian probe beam in the tissue using Monte Carlo simulations, and compare it to the extended Huygens-Fresnel model. Finally, we simulate the operation of the OCT system using a specially adapted Monte Carlo simulation code.