Phase-Function Corrected Diffusion Model for Diffuse Reflectance of a Pencil Beam Obliquely Incident on a Semi-Infinite Turbid Medium

Oblique incidence reflectometry (OIR) is an established technique for estimation of tissue optical properties, however, a sensing footprint of a few transport mean-free paths is often needed when diffusion-regime-based algorithms are used. Smaller-footprint probes require improved light-propagation models and inversion schemes for diffuse reflectance close to the point-of-entry but might enable micro-endoscopic form factors for clinical assessments of cancers and pre-cancers. In this paper we extend the phase-function corrected diffusion-theory presented by Vitkin et al. (Nat. Comm 2011) to the case of pencil beams obliquely incident on a semi-infinite turbid medium. The model requires minimal computational resources and offers improved accuracy over more traditional diffusion-theory approximations models when validated against Monte Carlo simulations. The computationally efficient nature of the models may lend themselves to rapid fitting procedures for inverse problems.