Virtual-source diffusion approximation for enhanced near-field modeling of photon-migration in low-albedo medium

Area of Science:

• Optics
• Biomedical Optics
• Photon Migration

Background:

• Standard analytical methods struggle with light propagation near collimated sources in turbid media.
• Existing discrete source models have limitations in specific scenarios.

Purpose of the Study:

• To develop an improved explicit model for light propagation in semi-infinite turbid media.
• To enhance the accuracy of diffuse approximation (DA) in the near-field and for low-albedo conditions.

Main Methods:

• Introduced a "Virtual Source" (VS) diffuse approximation (DA) model approximating collimated light as distributed isotropic point sources.
• Optimized VS parameters (intensities, locations) using a fitting procedure for near-field reflectance.
• Established an explicit 2VS-DA model with close-form derivations for practical application.

Main Results:

• The VS-DA model accurately describes photon migration in low-albedo media at short source-detector separations.
• The model retains the mathematical simplicity of standard DA while extending its validity.
• Comparisons with Monte Carlo simulations confirm the superiority of VS-DA over existing methods.

Conclusions:

• The proposed Virtual Source diffuse approximation (VS-DA) offers a significant advancement for modeling light propagation in turbid media.
• This method is particularly effective for near-field analysis and low-albedo scenarios.
• VS-DA provides a computationally efficient and accurate alternative to established methods.