Cardiac silhouette findings and mediastinal lines and stripes: radiograph and CT scan correlation.

Despite the increased use of CT imaging, chest radiography remains a very important diagnostic modality in the evaluation of lung parenchymal and mediastinal diseases, providing a vast amount of useful information. This information is generally derived from the relationships among the normal anatomic structures of the mediastinum, pleura, and lungs, which represent the basis of the "cardiac silhouette" and "mediastinal lines-and-stripes" concepts that potentially play an important role in the establishment of a diagnosis or a spectrum of diagnoses before proceeding to CT imaging. The capability of recognizing an abnormal chest radiograph on the basis of the displacement, deformation, or obscuration of one of these structures when compared with those in normal findings is often mandatory prior to requesting a potentially useful CT scan examination. Therefore, radiologists, trainees, and physicians must be familiar with the anatomic basis of those findings to be able to recognize the normal and abnormal appearance of structures when developing an appropriate differential diagnosis. In this review, we briefly describe the cardiac silhouette concepts and the mediastinal lines-and-stripes configurations as they relate to the radiographic and CT scan appearance of structures for a spectrum of pathologic diseases and list the possible underlying causes of the displacement, deformation, or obscuration of the structures.