An improved analytic function for predicting light fluence rate in circular fields on a semi-infinite geometry.

Area of Science:

• Biomedical Optics
• Photodynamic Therapy Research
• Medical Physics

Background:

• Accurate light fluence rate determination is crucial for effective photodynamic therapy (PDT) in preclinical and clinical settings.
• Existing models for light transport in biological tissues have limitations in range and accuracy.

Purpose of the Study:

• To compare longitudinal light fluence distribution in biological tissue for a 1 cm diameter circular light field.
• To develop an analytical expression fitting Monte Carlo simulation results for both circular and broad light beams.
• To express light transport parameters as a function of tissue optical properties.

Main Methods:

• Utilized Monte Carlo simulations for a semi-infinite turbid medium at an air-tissue interface.
• Investigated a range of in-vivo tissue optical properties, including absorption coefficients (μa) from 0.01 to 1 cm⁻¹ and reduced scattering coefficients (μs') from 2 to 40 cm⁻¹.
• Developed a 6-parameter model to describe light fluence distribution.

Main Results:

• The study presents a detailed comparison of light fluence distribution for a 1 cm diameter circular beam across various tissue optical properties.
• An analytical expression was derived to model light fluence distribution for both circular and broad beams, based on Monte Carlo simulations.
• The developed 6-parameter model demonstrates improved accuracy and applicable range for light transport predictions in biological tissues.

Conclusions:

• The 6-parameter model offers enhanced accuracy and range for predicting light transport through biological tissue.
• These findings can serve as a guide for optimizing light fluence distribution in photodynamic therapy based on known tissue optical properties.
• The study provides a foundation for more precise PDT treatment planning and execution.