Intrathoracic calcifications: radiographic features and differential diagnoses.

Intrathoracic calcifications occur in a wide variety of disorders. Although they are usually harmless sequelae of remote processes, calcifications provide important information for establishing the diagnosis or for evaluating the progression of known disease. They may arise in the pulmonary parenchyma, mediastinum, hilar and mediastinal lymph nodes, pleura, chest wall, or any combination of these structures. The cause of the calcification may be determined by means of the location and pattern of the calcifications within the lung parenchyma and knowledge of the associated clinical features. Calcifications in the thorax are frequently manifestations of previous infectious processes. Less often, they may be due to neoplasms, metabolic disorders, occupational exposure, or previous medical therapy. Large intrathoracid calcifications are usually identified on conventional chest radiographs; detection of smaller calcifications may require use of other imaging modalities, such as dual-energy digital radiography, fluoroscopy, radionuclide scanning, computed tomography (CT), and high-resolution CT.