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Proceedings Paper

Photochemical predictive analysis of photodynamic therapy with non-homogeneous topical photosensitizer distribution in dermatological applications
Author(s): I. Salas-García; F. Fanjul-Vélez; N. Ortega-Quijano; M. López-Escobar; J. L. Arce-Diego
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Paper Abstract

Photodynamic Therapy (PDT) is a therapeutic technique widely used in dermatology to treat several skin pathologies. It is based in topical or systemic delivery of photosensitizing drugs followed by irradiation with visible light. The subsequent photochemical reactions generate reactive oxygen species which are considered the principal cytotoxic agents to induce cell necrosis. In this work we present a PDT model that tries to predict the photodynamic effect on the skin with a topically administered photosensitizer. The time dependent inhomogeneous distribution of the photoactive compound protoporphyrin IX (PpIX) is calculated after obtaining its precursor distribution (Methyl aminolevulinate, MAL) which depends on the drug permeability, diffusion properties of the skin, incubation time and conversion efficiency of MAL to PpIX. Once the optical energy is obtained by means of the Beer Lambert law, a photochemical model is employed to estimate the concentration of the different molecular compounds taking into account the electronic transitions between molecular levels and particles concentrations. The results obtained allow us to know the evolution of the cytotoxic agent in order to estimate the necrotic area adjusting parameters such as the optical power, the photosensitizer concentration, the incubation and exposition time or the diffusivity and permeability of the tissue.

Paper Details

Date Published: 18 May 2010
PDF: 8 pages
Proc. SPIE 7715, Biophotonics: Photonic Solutions for Better Health Care II, 77152R (18 May 2010); doi: 10.1117/12.854635
Show Author Affiliations
I. Salas-García, Univ. de Cantabria (Spain)
F. Fanjul-Vélez, Univ. de Cantabria (Spain)
N. Ortega-Quijano, Univ. de Cantabria (Spain)
M. López-Escobar, Marqués de Valdecilla Univ. Hospital (Spain)
J. L. Arce-Diego, Univ. de Cantabria (Spain)

Published in SPIE Proceedings Vol. 7715:
Biophotonics: Photonic Solutions for Better Health Care II
Jürgen Popp; Wolfgang Drexler; Valery V. Tuchin; Dennis L. Matthews, Editor(s)

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