Photodynamic therapy (PDT) is the selective destruction of abnormal cells by exposure to light. Its primary field of application is cancer treatment. Selectivity is achieved by treatment of the cells with a photosensitizer, the purpose of which is to transduce absorption of light from an external source into generation of cytotoxic reactive oxygen species (ROS). The therapeutic effect is controlled by the dosage of drug (photosensitizer) and the dosage of light. For this purpose, Lumencor’s solid-state light engines offer precision illumination control in the form of feedback regulation and metering of light output.