Experimental determination of threshold dose in photodynamic therapy in normal rat liver

Using normal rat liver we investigated the depth of necrosis induced by photodynamic therapy when different light doses and photosensitizer (Photgem (R)) concentrations. All experiments were done with a fluence rate of 250 mW/cm(2). Photosensitizer concentration was varied from 1.0, 1.5, 2.0, and 5.0 mg/kg of body weight and it was administered through the left tail vein. For each photosensitizer concentration the light dose was varied from 10, 50, 100, 150, and 200 J/cm(2). Each experimental point was done using five animals. The depth of necrosis analysis allows us to determine the threshold dose and compare its value with the existent results in the literate. Our result suggested a value about 3 times higher than the conventionally adopted value. It indicates the dependence of such value with the employed concentration photosensitizer. The use of simple models to understand basic features of the PDT (Photodynamic Therapy) may contribute to the solid establishment of dosimetry in PDT enhancing its use in the clinical management of cancers and others lesions.