Author: Hongjing Sun, Timothy C. Zhu 👨🔬
Affiliation: University of Pennsylvania 🌍
Purpose: This study aims to develop a model of singlet oxygen distribution in pleural photodynamic therapy (PDT) by combining standardized anatomical coordinates with CT-validated geometry reconstruction and quantified drug heterogeneity patterns. We seek to establish a comprehensive framework for treatment optimization incorporating both geometric accuracy and drug distribution effects.
Methods: Pleural cavity geometry was reconstructed using navigation data and validated against post-treatment CT imaging. The cavity reconstruction was oriented to a standardized coordinate system with consistent detector position alignment. Photofrin concentrations were measured at multiple sampling sites within the pleural cavity, revealing significant inter-patient heterogeneity. This heterogeneous drug distribution data was mapped onto the standardized geometry and integrated into COMSOL Multiphysics for singlet oxygen modeling. Clinical data from 11 cases were used for a more comprehensive understanding.
Results: Geometric validation showed excellent agreement between navigation-based reconstruction and CT imaging. Photofrin concentration measurements demonstrated substantial spatial heterogeneity, ranging from approximately 0.5 to 4.5 mg/kg across different cavity regions. The COMSOL simulation incorporating this heterogeneity predicted singlet oxygen concentrations varying from 0.21 to 0.96 mM, with distinct patterns corresponding to both anatomical features and local drug distribution.
Conclusion: Our CT-validated geometric standardization combined with quantified drug heterogeneity provides an improved platform for modeling PDT dosimetry. The observed variations in both drug distribution and resulting singlet oxygen generation highlight the importance of patient-specific modeling for treatment optimization. This validated approach enables more accurate identification of potentially under-treated regions and could support real-time treatment guidance systems.