Decay behavior and optical parameter identification for spatial-frequency domain imaging by the radiative transport equation

TL;DR

This paper analyzes how light decay in spatial-frequency domain imaging (SFDI) is governed by the radiative transport equation, explaining the method's ability to focus on shallow regions and extract top-layer optical properties.

Contribution

It provides a theoretical analysis of decay modes in SFDI using the radiative transport equation, linking decay rates to spatial frequencies and eigenvalues, and demonstrates optical property identification in layered media.

Findings

Decay modes are superpositions with rates determined by spatial frequencies and eigenvalues.

Nonzero spatial frequency light decays rapidly, enabling top-layer property extraction.

Optical properties of a top layer are successfully measured in layered phantoms.

Abstract

The decay behavior of the specific intensity is studied for the spatial-frequency domain imaging (SFDI). It is shown using the radiative transport equation that the decay is given by a superposition of different decay modes, and the decay rates of these modes are determined by spatial frequencies and Case's eigenvalues. This explains why SFDI can focus on shallow regions. The fact that light with nonzero spatial frequency rapidly decays makes it possible to exclusively extract optical properties of the top layer of a layered medium. We determine optical properties of the top layer of a solid phantom. This measurement is verified with different layered media of numerical phantoms.