photodynamic therapy

photodynamic therapy A form of treatment that uses a photosensitizing agent, administered by mouth or intravenously, which concentrates selectively in certain cells, followed by exposure of the involved tissue to a special light (such as laser or ultraviolet light), in order to destroy as much of the abnormal tissue as possible. For example, photodynamic therapy is used to treat some forms of cancer and psoriasis. Also known as photochemotherapy.