Scintigraphic appearance of bone during external beam irradiation

Separate imaging studies employing Tc-99m MDP, In-111 labeled leukocytes, and Tc-99m SC were performed in a patient receiving external beam radiation therapy to the mediastinum and left hemithorax. The leukocyte scan demonstrated greatly increased activity at the site of the radiation port. The bone marrow (sulfur colloid) scan was normal and the bone scan demonstrated only minimally increased activity in the irradiated region. The varying appearance of these scans may represent the difference in the early effect of radiation on bone and bone marrow elements.