Treatment parameters affecting the response of normal brain to photodynamic therapy

Different aspects of photodynamic therapy in normal rat brain tissue have been studied, in an effort to understand and improve the dosimetry of this new modality in treatment of brain tumors. dosimetry parameters, including light energy dose, fluence rate and beam size, and drug dosage were studied. PDT induced lesion depth in brain was measured as a biological endpoint. Effective attenuation depth and absolute light fluence rate distribution under superficial irradiation were measured using invasive optical probes. Photosensitizer uptake was quantified using HPLC analysis. The results indicate that normal brain have a high intrinsic sensitivity to PDT treatment, based on the estimated photodynamic threshold.