A method for treating arteriosclerotic lesions is provided wherein the method is characterized by administering a chemical compound to the patient, the compound being a porphyrin complexed with a radioactive metal. Cells which exhibit an affinity for the porphyrin element indicate sites of plaque buildup. The radioactive metal within the compound is cytotoxic to cells in and surrounding the plaque and may allow tomographic scanning of the plaque as well. The complexed compound can be introduced to the patient a desired number of times to provide the necessary radiation treatment and ongoing monitoring of plaque removal.