Contribution of various scattering orders to OCT images of skin

摘要

Simulated OCT images of skin were obtained implementing Monte Carlo simulations. The multilayer skin model used in simulations was based on the experimental OCT images obtained at the wavelength of 910 nm. The following skin layers were considered in the model: stratum corneum, epidermis prickle layer, epidermis basal layer, dermis with upper plexus, dermis, and dermis with lower plexus. The images were obtained both with and without speckle accounting. The latter case is calculated from the envelopes of calculated interference signals while the former accounts for the interference fringe patterns. The contributions of least and multiple scattering, diffusive and non-diffusive components of the backscattered light to the resulting OCT image were separated and analyzed. It was shown that least scattering contribution represents the imaging of the upper skin layers, while multiple scattering contribution can be characterized as blurred image with reduced contrast preserving, however, essential details. The least scattering component contributes to the image for optical depth up to 1 mm. From the analysis of the contribution of non-diffusive and diffusive components it follows that the diffusive component contributes to imaging the object starting from the epidermis basal layer and is more blurred compared to the multiple scattering contribution. The non-diffusive component contributes to the image for optical depth up to 1.3 mm. The effect of coherence length on the contributions of least and multiple scattering was also studied. It was shown, that contribution of multiple scattering increases with a decrease of the coherence length.