8 February 2011 A dynamic model for ALA-PDT of skin: analysis of the correlation of fluorescence and singlet oxygen luminescence to spatial distribution of singlet oxygen
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Abstract
Both photosensitizer fluorescence photobleaching and singlet oxygen luminescence (SOL) have been measured during ALA-PDT of skin in attempts to estimate PDT dose. However, the relationship of these detected signals to singlet oxygen (1O2) dose in a given volume and to its depth distribution are not well understood and difficult to verify experimentally because of the temporal and spatial variations of the essential parameters in PDT. A model for ALA-PDT of normal human skin was developed to simulate the dynamic progress of PDT. The model incorporates Monte Carlo simulations of excitation light fluence and both SOL and PpIX fluorescence signals, 1O2-mediated photobleaching mechanism, ground-state oxygen (3O2) diffusion and perfusion, a cumulative 1O2-dependent threshold vascular response and any initial distribution of PpIX. The simulated time-resolved evolution of the instantaneous PpIX fluorescence photobleaching and cumulative SOL signals are examined as functions of irradiance and related to both the time-resolved distribution of cumulative 1O2 production at various depths and the average dose in the dermis. The simulations used a green light source at 523 nm. The correlation of SOL signals with the average dose was found to be less irradiance-dependent than that of fluorescence photobleaching, which indicates the great potential of SOL as a clinical dosimetric tool in PDT.
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Baochang Liu, Baochang Liu, Thomas J. Farrell, Thomas J. Farrell, Michael S. Patterson, Michael S. Patterson, } "A dynamic model for ALA-PDT of skin: analysis of the correlation of fluorescence and singlet oxygen luminescence to spatial distribution of singlet oxygen", Proc. SPIE 7886, Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy XX, 78860F (8 February 2011); doi: 10.1117/12.874194; https://doi.org/10.1117/12.874194
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