Physiological Considerations Acting on Triplet Oxygen for Explicit Dosimetry in Photodynamic Therapy

Publication date: Available online 25 July 2017
Source:Photodiagnosis and Photodynamic Therapy
Author(s): Víctor Sánchez, María Paulina Romero, Sebastião Pratavieira, César Costa
The aims of this study were to determine the spatial and temporal theoretical distribution of the concentrations of Protoporphyrin IX, ³O2 and doses of ¹O2. The type II mechanism and explicit dosimetry in photodynamic therapy were used. Furthermore, the mechanism of respiration and cellular metabolism acting on ³O2 were taken into account. The dermis was considered as an absorbing and a scattering medium. An analytical solution was used for light diffusion in the skin. The photophysical, photochemical and biological effects caused by PDT with the initial irradiances of 20, 60 and 150mW/cm² were studied for a time of exposure of 20min. and a maximum depth of 0.5cm. We found that the initial irradiance triples its value in 0.02cm and that almost 100% of PpIX is part of the dynamics of reactions in photodynamic therapy. Additionally, with about 40μMof ³O2 there is a balance between the consumed and supplied oxygen. Finally, we determined that with 60mW/cm², the highest dose of ¹O2 is obtained.



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