title: Optimization of physiological parameter for macroscopic modeling of reacted singlet oxygen concentration in anin-vivomodel.
abstract: Singlet oxygen (1O2) is generally believed to be the major cytotoxic agent during photodynamic therapy (PDT), and the reaction between1O2and tumor cells define the treatment efficacy. From a complete set of the macroscopic kinetic equations which describe the photochemical processes of PDT, we can express the reacted1O2concentration, [1O2]rx, in a form related to time integration of the product of1O2quantum yield and the PDT dose rate. The production of [1O2]rxinvolves physiological and photophysical parameters which need to be determined explicitly for the photosensitizer of interest. Once these parameters are determined, we expect the computed [1O2]rxto be an explicit dosimetric indicator for clinical PDT. Incorporating the diffusion equation governing the light transport in turbid medium, the spatially and temporally-resolved [1O2]rxdescribed by the macroscopic kinetic equations can be numerically calculated. A sudden drop of the calculated [1O2]rxalong with the distance following the decrease of light fluence rate is observed. This suggests that a possible correlation between [1O2]rxand necrosis boundary may occur in the tumor subject to PDT irradiation. In this study, we have theoretically examined the sensitivity of the physiological parameter from two clinical related conditions: (1) collimated light source on semi-infinite turbid medium and (2) linear light source in turbid medium. In order to accurately determine the parameter in a clinical relevant environment, the results of the computed [1O2]rxare expected to be used to fit the experimentally-measured necrosis data obtained from anin vivoanimal model.
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA 19104.
authors.forename: Ken Kang-Hsin
authors.initials: KK
authors.lastname: Wang
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA 19104.
authors.forename: Theresa M
authors.initials: TM
authors.lastname: Busch
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA 19104.
authors.forename: Jarod C
authors.initials: JC
authors.lastname: Finlay
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA 19104.
authors.forename: Timothy C
authors.initials: TC
authors.lastname: Zhu
keywords: PDT dosimetry; Photodynamic therapy; light transport; oxygen diffusion; singlet oxygen