Phase analysis method for characterizing absorption in turbid media: theory, simulations, and TiO₂ phantom...

Area of Science:

• Biophotonics
• Optical characterization
• Turbid media analysis

Background:

• Separating absorption and scattering in turbid media is a significant challenge in optical characterization.
• Existing methods often struggle to independently quantify these optical properties.

Purpose of the Study:

• To develop and validate a non-contact method for estimating the absorption coefficient (µa) using phase analysis.
• To extend the iterative multi-plane optical properties extraction (IMOPE) technique for absorption assessment.

Main Methods:

• Applied a phase-analysis framework, originally for reduced scattering coefficient (µs') extraction, to estimate µa.
• Extended the diffuse-reflectance (DR) model to include sensitivity to µa variations.
• Validated using Monte Carlo simulations and TiO2-based phantoms with controlled optical properties.

Main Results:

• Demonstrated opposing trends for µa and µs' increments within the phase-analysis framework.
• Experimentally validated the phase-based µa extraction scheme with 91% and 95% agreement at 473 nm and 632.8 nm, respectively.
• Provided a detailed TiO2 phantom preparation protocol for reproducibility.

Conclusions:

• Established a route for phase-driven absorption assessment in turbid media.
• Presented an initial framework for estimating µa from reconstructed phase data.
• Laid the groundwork for future quantitative separation of absorption and scattering.