Fig. 1.

Anatomical scheme of the pleural cavity and the chest wall and disease of abnormal air collection in each anatomical space. Axial chest CT of a 50-year-old man with chronic empyema shows fluid collection in the pleural cavity and thickened pleura. The CT shows the visceral pleura (white arrowheads), pleural cavity (PC), parietal pleura (black arrowheads), extrapleural fat (EF), innermost intercostal muscle and endothoracic fascia (white asterisks), and intercostal fat (IF). The innermost intercostal muscle is normally defective in the dorsal mediastinal side of the chest wall