Multiple passages of light through an absorption inhomogeneity in optical imaging of turbid media

TL;DR

This paper analyzes how multiple light passages through absorption inhomogeneities affect optical imaging in turbid media, highlighting the significance of nonlinear corrections for larger, high-contrast inhomogeneities.

Contribution

It introduces a self-energy diagram approach to quantify nonlinear corrections in optical imaging of deep inhomogeneities, validated by Monte Carlo simulations.

Findings

Nonlinear correction increases with inhomogeneity size and contrast.

Correction factor aligns well with Monte Carlo simulations.

Significant correction (50-75%) in near-infrared for tissue-like properties.

Abstract

The multiple passages of light through an absorption inhomogeneity of finite size deep within a turbid medium is analyzed for optical imaging using the ``self-energy'' diagram. The nonlinear correction becomes more important for an inhomogeneity of a larger size and with greater contrast in absorption with respect to the host background. The nonlinear correction factor agrees well with that from Monte Carlo simulations for CW light. The correction is about $50%-75%$ in near infrared for an absorption inhomogeneity with the typical optical properties found in tissues and of size of five times the transport mean free path.