title: A theoretical comparison of macroscopic and microscopic modeling of singlet oxygen during Photofrin and HPPH mediated-PDT.
abstract: Mathematic models were developed to simulate the complex dynamic process of photodynamic therapy (PDT). Macroscopic or microscopic modeling of singlet oxygen (1O2) is particularly of interest because it is the major cytotoxic agent causing biological effects during PDT. Our previously introduced macroscopic PDT model incorporates the diffusion equation for the light propagation in tissue and the macroscopic kinetic equations for the production of the1O2. The distance-dependent distribution of3O2and reacted1O2can be numerically calculated using finite-element method (FEM). We recently improved the model to include microscopic kinetic equations of oxygen diffusion from uniformly distributed blood vessels and within tissue. In the model, the cylindrical blood capillary has radius in the range of 2-5μm and a mean length of 300μm, and supplies oxygen into tissue. The blood vessel network is assumed to form a 2-D square grid perpendicular to a linear light source. The spacing of the grid is 60μm. Oxygen can also diffuse along the radius and the longitudinal axial of the cylinder within tissue. The oxygen depletion during Photofrin-PDT can be simulated using both macroscopic and microscopic approaches. The comparison of the simulation results have reasonable agreements when velocity of blood flow is reduced during PDT.
authors.affiliation: Department of Radiation Oncology, School of Medicine, University of Pennsylvania, Philadelphia, PA 19104.
authors.forename: Baochang
authors.initials: B
authors.lastname: Liu
authors.affiliation: Department of Radiation Oncology, School of Medicine, University of Pennsylvania, Philadelphia, PA 19104.
authors.forename: Michele M
authors.initials: MM
authors.lastname: Kim
authors.affiliation: Department of Radiation Oncology, School of Medicine, University of Pennsylvania, Philadelphia, PA 19104.
authors.forename: Timothy C
authors.initials: TC
authors.lastname: Zhu
keywords: Photodynamic therapy; Photofrin; dosimetry; macroscopic model; microscopic model; singlet oxygen