Origin of improved depth penetration in dual-axis optical coherence tomography: a Monte Carlo study.

Recent studies have demonstrated that extended imaging depth can be achieved using dual-axis optical coherence tomography (DA-OCT). By illuminating and collecting at an oblique angle, multiply forward scattered photons from large probing depths are preferentially detected. However, the mechanism behind the enhancement of imaging depth needs further illumination. Here, the signal of a DA-OCT system is studied using a Monte Carlo (MC) simulation. We modeled light transport in tissue and recorded the spatial and angular distribution of photons exiting the tissue surface. Results indicate that the spatial separation and offset angle created by the non-telecentric scanning configuration promote the collection of more deeply propagating photons than conventional on-axis OCT. Photons with greater probing depths have higher probabilities to exit the tissue surface further away from the incident position. Therefore, by illuminating and collecting at an oblique angle, the DA-OCT system favors the detection of deep propagating photons. This article is protected by copyright. All rights reserved.