<b>General</b>

Radiation therapy is used to treat many intrathoracic and chest wall malignancies. A variety of changes may occur after radiation therapy to the thorax. In the chest, irradiation indicates potential for injury to arteries, ribs, nerves, and esophagus, as well as to the heart and lungs.

Radiation therapy produces dramatic effects in the lung. Radiation pneumonitis [lung inflammation] can be a major complication for patients receiving chest irradiation. Pulmonary necrosis is an uncommon, severe, late complication of adjuvant postoperative irradiation. Bronchiolitis obliterans with organizing pneumonia is a distinct separate entity characterized by patchy, migratory, peripheral air-space infiltrates. Radiation therapy can also cause spontaneous pneumothorax, mesothelioma, and lung cancer. In the mediastinum, radiation therapy may cause thymic cysts, calcified lymph nodes, and esophageal injuries. 

<b>Cardiovascular</b> complications of radiation therapy are often delayed and insidious. Premature coronary artery stenosis occurs after radiation therapy to the mediastinum. Radiation therapy may also give rise to calcifications of the ascending aorta, pericardial disease, valvular injuries, and conduction abnormalities. Women who undergo chest irradiation before the age of 30 years have a high risk of developing a second breast cancer. Radiation-induced sarcomas are an infrequent but well-recognized complication of radiation therapy. Other chest wall injuries due to radiation therapy are osteochondroma and rib or clavicle [collar-bone] fractures.
 
When irradiating the mediastinum for malignancy, the radiotherapeutic technique (site and number of fields, division of dose), and especially the dose absorbed, seem to be relatively closely related to the frequency and severity of the post-irradiation lesions of the heart and lung. 

Knowledge of the imaging features of injuries caused by radiation therapy can prevent misinterpretation as recurrent tumor and may facilitate further treatment. <b>Additional or returning symptoms may indicate recurrence OR metastasis of original tumor, OR radiation damage, OR a New Cancer developing at that site</b>. Differentiation of radiation pathology from recurrent or metastatic tumor or new malignancy can be difficult.