Monte Carlo simulation of light fluence in tissue in a cylindrical diffusing fibre geometry

Area of Science:

• Biomedical Optics
• Medical Physics
• Photodynamic Therapy

Background:

• Accurate modeling of light propagation is crucial for effective photodynamic therapy (PDT).
• Linear light diffusers are commonly used in PDT for treating hollow organs.
• Understanding light distribution within these organs is essential for optimizing treatment efficacy.

Purpose of the Study:

• To investigate light propagation from a linear diffuser within a cylindrical hollow organ using the Monte Carlo (MC) method.
• To provide quantitative and qualitative data to aid in the planning of PDT.
• To assess the impact of varying optical properties and diffuser characteristics on light distribution.

Main Methods:

• Utilized the Monte Carlo (MC) method to simulate light propagation.
• Input parameters included cavity dimensions, optical coefficients (absorption, scattering, anisotropy), refractive indices, and light diffuser properties.
• Validated MC model results using a tissue-simulating phantom irradiated at 633 nm.

Main Results:

• Simulations provided data on light penetration and fluence rate build-up across a range of optical coefficients.
• Isofluence curves showed potential shifts and spreads along the axis, influenced by lumen diameter and diffuser emission profile.
• Demonstrated that inaccuracies in optical coefficients can significantly affect calculated light doses.

Conclusions:

• The MC model effectively simulates light propagation for PDT planning in hollow organs.
• Geometric and optical parameters critically influence light distribution and dose delivery.
• The study offers valuable data for optimizing PDT protocols and estimating dose uncertainties.