Abstract
Singlet oxygen ( 1O 2) is generally believed to be the major cytotoxic agent during photodynamic therapy (PDT), and the reaction between 1O 2 and 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 reacted 1O2 concentration, [ 1O 2]rx, in a form related to time integration of the product of 1O 2 quantum yield and the PDT dose rate. The production of [ 1O 2]rx involves physiological and photophysical parameters which need to be determined explicitly for the photosensitizer of interest. Once these parameters are determined, we expect the computed [ 1O 2]rx to be an explicit dosimetric indicatorfor clinical PDT. Incorporating the diffusion equation governing the light transport in turbid medium, the spatially and temporally-resolved [ 1O 2]rx described by the macroscopic kinetic equations can be numerically calculated. A sudden drop of the calculated [ 1O 2]rx along with the distance following the decrease of light fluence rate is observed. This suggests that a possible correlation between [ 1O 2]rx and 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 [ 1O 2]rx are expected to be used to fit the experimentally-measured necrosis data obtained from an in vivo animal model.
Original language | English (US) |
---|---|
Article number | 71640O |
Journal | Progress in Biomedical Optics and Imaging - Proceedings of SPIE |
Volume | 7164 |
DOIs | |
State | Published - 2009 |
Externally published | Yes |
Event | Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy XVIII - San Jose, CA, United States Duration: Jan 24 2009 → Jan 25 2009 |
Keywords
- Light transport
- Oxygen diffusion
- PDT dosimetry
- Photodynamic therapy
- Singlet oxygen
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Biomaterials
- Atomic and Molecular Physics, and Optics
- Radiology Nuclear Medicine and imaging