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BASIC RADIOLOGIC ANATOMY OF THE CHEST

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In order to identify pathologic changes in the chest, it is important to understand the radiologic anatomy. Since chest radiography and CT are the primary modalities for imaging the chest, these will be depicted in Figs. 4.1 to 4.6. While the heart and lungs are the dominant structures in the chest, it is important to remember that many other important structures are depicted on radiographs and CT scans of the chest, such as the great vessels, esophagus, tracheobronchial tree, rib cage, etc. Many of these structures are contained within the mediastinum. For practical purposes, it is useful to compartmentalize the mediastinum as described by Felson [1]. The anterior and middle mediastinum are divided on the lateral chest radiograph by a line extending along the anterior tracheal border and inferiorly along the posterior border of the heart. The middle and posterior mediastinum are separated by a line 1 cm posterior to the anterior margin of the thoracic vertebral bodies. While this differs from traditional anatomic boundaries, it proves useful radiographically.

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Fig. 4.1.

Normal PA view of the chest. This is a female patient (note the breast shadows). White arrowheads denote the right paratracheal stripe. This is normally 4 mm or less in thickness. The white arrow annotates the aortic knob, which is created by the aortic arch being seen somewhat en face, slightly oblique. The black arrow denotes the AP window. The hilar angles are demarcated bilaterally by the black arrowheads, and are normally concave as in this patient. The right heart border (mostly the right atrium) is border forming with the right middle lobe, and the left heart border (mostly the left ventricle) is border forming with the lingula.

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Fig. 4.2.

Normal PA view of the chest. This is the same study as Figs. 4.1; however, the window and level settings have been adjusted to allow for improved visualization of the mediastinal borders. Black arrowheads annotate the lateral border of the descending aorta. Black arrows demarcate the left paraspinal stripe. White arrowheads demonstrate the anterior junction line, formed where the pleura of the right and left lungs appose anteriorly. Finally, the azygoesophageal recess is marked by white arrows, formed by the interface of the right lower lobe with the esophagus and azygous vein. Please note the importance of altering window/level settings in order to maximize visualization of normal anatomic structures and therefore pathology as well.

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Fig. 4.3.

Normal lateral chest radiograph. RS denotes the retrosternal clear space. An opacity in this region would suggest an anterior mediastinal mass. Black arrowheads mark the posterior wall of the trachea. Thin black arrows denote the posterior wall of the ...

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