Radiation-induced lung disease and the impact of radiation methods on imaging features

Although radiologic findings in radiation-induced lung disease are well described in the literature, the influence exerted on these findings by different radiation methods is not well understood. Radiation treatment of non-small cell lung cancer varies depending on the location and extent of disease. Irradiation with oblique beam angles results in unusual distribution of radiation-induced lung disease. Small cell lung cancer is treated with irradiation concurrent with or following chemotherapy, and portal arrangements are controversial. In breast cancer, use of tangential beam portals may induce radiation pneumonitis or fibrosis at the peripheral lung anterolaterally. Use of supraclavicular portals may produce lesions in the lung apex that appear similar to pulmonary tuberculosis. In esophageal cancer, radiation portals with a 5-6-cm margin above and below the tumor are generally recommended, and computed tomography (CT) frequently demonstrates radiation-related lung damage adjacent to the mediastinum. In mediastinal tumors, the mantle field includes all the major lymph node regions above the diaphragm. Radiation pneumonitis varies from minimal to extremely marked change in the paramediastinal areas and in both apices. CT is more sensitive to radiation-induced lung disease than chest radiography and demonstrates related changes earlier. Furthermore, it more clearly depicts the precise distribution and pattern of disease. Familiarity with the imaging findings in radiation-induced lung disease produced by different radiation methods will help radiologists interpret abnormalities seen at chest radiography and CT in affected patients.