Conventional chest radiographs: anatomic understanding of newer observations.

Despite the advances in medical imaging modalities over the past several years, conventional chest radiography still remains the most commonly performed imaging examination. In this report, the author discusses four radiographic observations, all visible on the conventional chest radiograph, and the anatomic basis for each: (a) the normal apical opacity, produced by the subclavian artery and easily confused with parenchymal abnormality; (b) vascular reorientation with upper lobe volume loss, a characteristic divergent or parallel pattern helpful in recognizing upper lobe volume loss; (c) extrapleural fat, which simulates pleural plaques along the lateral chest walls and pleural thickening at the chest apices; and (d) mobility of the mediastinum, which contributes to incorrect mediastinal mass localization and creates soft-tissue bands in the retrosternal area.