Photochemical model of photodynamic therapy applied to skin diseases by a topical photosensitizer

Photodynamic Therapy (PDT) provides a non-invasive, efficient and safe treatment for skin diseases with good cosmetic results. These characteristics make this technique more advantageous than radiotherapy or chemotherapy, which present limitations in a big number of lesions, are painful in many cases and produce non-satisfactory cosmetic results. We present the clinical results obtained at present by this optical technique and a photochemical model of the PDT process applied to the skin by means of a topical photosensitizer, in order to find the optimal PDT parameters. Optical propagation inside the tissue is calculated by means of the three dimensional Beer-Lambert law, due to its facility to be integrated in the differential equations system used to model the photochemical processes involved. With this information it is possible to obtain an initial estimation about the optimal drug dose and the optical power required.