The great selectivity and the lack of side effects of Photodynamic Therapy make it more advantageous than radiotherapy or chemotherapy. The application of PDT to skin diseases is particularly appropriate, due to the accessibility of this tissue. Common disorders like nonmelanoma skin cancer, that includes basocelullar or squamous cell carcinomas, can be treated with PDT. Conventional procedures, like surgery or radiotherapy, are not so efficient and do not, in general, obtain the same favourable results. PDT in dermatology medical praxis uses fixed protocols depending on the photosensitizer and the optical source used. These protocols are usually provided by the photosensitizer laboratory, and every lesion is treated with the same parameters. In this work we present a photo-chemical model of PDT applied to skin disorders treated with topical photosensitizers. Optical propagation inside the tissue is calculated by means of a 3D diffusion equation, solved via a finite difference numerical method. The photosensitizer degradation or photobleaching is taken into account, as the drug looses efficiency with the irradiation time. With these data the necrosis area is estimated, so this model could be used as a predictive tool to adjust the optical power and exposition time for the particular disease under treatment.

Date Published: 19 February 2009
PDF: 8 pages
Proc. SPIE 7161, Photonic Therapeutics and Diagnostics V, 71610P (19 February 2009); doi: 10.1117/12.809049

Published in SPIE Proceedings Vol. 7161:
Photonic Therapeutics and Diagnostics V
Henry Hirschberg M.D.; Brian Jet-Fei Wong M.D.; Kenton W. Gregory M.D.; Reza S. Malek; Nikiforos Kollias; Bernard Choi; Guillermo J. Tearney; Justus F. R. Ilgner; Steen J. Madsen; Laura Marcu; Haishan Zeng, Editor(s)