Articles techniques et présentations

Singlet oxygen (¹O₂) is the major cytotoxic agent in photodynamic therapy (PDT). The reaction between ¹O₂ and tumor cells defines the treatment efficacy. Based on a previously developed model that incorporates the diffusion equation for the light transport in tissue and the macroscopic kinetic equations for the generation of the singlet oxygen, the distance-dependent reacted ¹O₂ is numerically calculated using finite-element method (FEM) on COMSOL. The formula of reacted ¹O₂ concentration involves 5 photophysiological parameters which need to be determined explicitly to predict the generation of ¹O₂. We have developed an algorithm to iteratively calculate the singlet oxygen concentration profile and compare with the measurements to obtain an optimal set of parameters. The optimization is performed using Matlab and dynamically linked with COMSOL for the forward calculation. The sensitivity of the model parameters to the necrosis depths and treatment conditions are examined. Our algorithm is capable of robustically determining the parameters with a total calculation time of less than 30 seconds.