Mediastinal lines, stripes and interfaces on PA chest radiograph with CT correlations

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1 Mediastinal lines, stripes and interfaces on PA chest radiograph with CT correlations Award: Certificate of Merit Poster No.: C-0442 Congress: ECR 2013 Type: Educational Exhibit Authors: N. Bystrická, H. Poláková, J. Sykora; Bratislava/SK Keywords: Neoplasia, Normal variants, CT, Conventional radiography, Oncology, Mediastinum, Anatomy DOI: /ecr2013/C-0442 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 30

2 Learning objectives to illustrate the anatomical basis of the mediastinal lines, stripes and interfaces to outline normal and pathologic conditions that may alter the appearance of these reflections to give examples of the radiographic findings that help localize abnormalities in the anterior, middle or posterior mediastinum Background A variety of mediastinal reflections can be identified at conventional radiography (Fig. 1 on page 3) These reflections represent mediastinal lines, stripes and interfaces. mediastinal lines are thin (<1mm in width) linear opacities that result from contact between two aerated structures outlining thin intervening tissue on both sides, such as the anterior and posterior junction lines. mediastinal stripes are bands that result from air outlining thicker intervening mediastinal structure. The mediastinal stripes present on PA chest radiographs include the right and left paratracheal stripes. mediastinal interfaces, or edges, are produced by contact between aerated lung and adjacent mediastinal structures. The mediastinal interfaces include the right and left paraspinal lines, the azygoesophageal recess, the aortic pulmonary stripe, the paraortic line and cardiac borders. The frequency of visualization of these reflections on chest radiographs is variable (Table 1 on page 4), therefore the absence of one of the mediastinal lines, stripes or interfaces may be insignificant as it may be caused by anatomic variations or by technical conditions. However, presence, obliteration, thickening or distortion of these lines, stripes and edges can reveal mediastinal disease. These findings can be also used to localize mediastinal masses in the anterior, middle or posterior mediastinum (Table 2 on page 4) and therefore may help narrow the differential diagnosis (Table 3 on page 5) and determine the most appropriate further diagnostic workup. Page 2 of 30

3 Abbreviations: PA = posteroanterior CT = computed tomography Cor MPR = coronal multiplanar reconstruction Sag MPR = sagittal multiplanar reconstruction SVC = superior vena cava IVC = inferior vena cava AP = aortic-pulmonary LN = lymph nodes Images for this section: Fig. 1: Mediastinal reflections on frontal chest radiographs. Page 3 of 30

4 Table 1: Frequency of visualization of different mediastinal reflections on frontal chest radiographs (2). Page 4 of 30

5 Table 2: Radiographic findings that help localize a mediastinal lesion within the anterior, middle or posterior mediastinum. Page 5 of 30

6 Table 3: Differential diagnosis of a mediastinal mass by anatomic location. Page 6 of 30

7 Imaging findings OR Procedure details 1. Anterior Junction Line Anatomy: Anterior junction line results from the anterior apposition of the lungs, which lies behind the upper two-thirds of the sternum. The line consists of four layers of pleura and a variable amount of intervening fat. Normal radiographic appearance: Anterior junction line appears as a thin oblique line projecting over the superior two-thirds of the sternum and runs from the upper right to the lower left. It does not extend above the level of clavicles. (Fig. 2 on page 12). Abnormal radiographic appearance: It may be absent when its course is not tangential to the X-ray beam. It can be obscured by other structures such as the heart, great vessels or the thoracic spine. Obliteration or abnormal convexity suggests anterior mediastinal disease (Fig. 3 on page 12), although it is usually the preservation of more posterior lines at radiography, that helps identify the location of an anterior mediastinal mass. Displacement of the line may be due to hyperinflation or volume loss of the surrounding lung (Fig. 4 on page 13). 2. Posterior Junction Line Anatomy: Posterior junction line results from the apposition of the lungs posterior to the esophagus rd th and anterior to the 3 to 5 thoracic vertebrae. Similarly to anterior junction line, it is formed by four layers of pleura. Normal radiographic appearance: Posterior junction line appears as a thin straight line projecting through the trachea. Unlike anterior junction line, it can be seen above the clavicles (Fig. 5 on page 14). Page 7 of 30

8 Abnormal radiographic appearance: Abnormal bulging, convexity or obliteration of this line suggests a posterior mediastinal abnormality. Further clues to the location of a mass can be inferred from the lateral margins of the mass above the clavicles (Fig. 6 on page 15). 3. Right Paratracheal Stripe Anatomy: The right paratracheal stripe is formed by the tracheal wall, mediastinal connective tissue and paratracheal pleura. Air within the trachea and the aerated right upper lobe outline the intervening soft tissues. Normal radiographic appearance: The right paratracheal stripe begins at the level of the clavicles and extends inferiorly, projecting through the superior vena cava, to the right tracheobronchial angle at the level of azygos arch (Fig. 7 on page 16). This stripe has a maximum normal thickness of 4mm and it should be uniform in width. Abnormal radiographic appearance: An abnormal contour, widening or obliteration of this stripe may be due to abnormality of any of its components, from the tracheal mucosa to the pleural space, such as tracheal carcinoma, paratracheal masses (most commonly lymphadenopathy) and pleural effusion or thickening (Fig. 8 on page 17). 4. Left Paratracheal Stripe Anatomy: Similarly to the right paratracheal stripe, the left paratracheal stripe is formed by tracheal wall, variable amount of mediastinal fat and paratracheal pleura. Air within the trachea and the aerated left upper lobe outline the intervening soft tissues. Normal radiographic appearance: The left paratracheal stripe extends superiorly from the aortic arch to join with the reflection from the left subclavian artery. It may be obscured by contact between the Page 8 of 30

9 left upper lobe and either the proximal left common carotid artery anteriorly or the left subclavian artery posteriorly (i.e. by the pararterial line) (Fig. 7 on page 16). Abnormal radiographic appearance: An abnormal contour or widening may be caused by pleural effusions or thickening, paratracheal lymphadenopathy, hematomas or neoplasm (Fig. 8 on page 17.). 5. Aortic-Pulmonary Window Reflection Anatomy: AP window represents a mediastinal region bounded anteriorly by the ascending aorta, posteriorly by the descending aorta, superiorly by the aortic arch, and inferiorly by the left pulmonary artery. The medial border is formed by the ligamentum arteriosum, whereas the lateral aspect forms the interface between the left lung and the mediastinum known as the aortic-pulmonary window reflection. Normal radiographic appearance: On a frontal radiograph, the AP window reflection extends from the aortic knob to the left pulmonary artery (Fig. 9 on page 18). This should have a concave or straight border, however, a straight contour should be considered abnormal if previous studies demonstrated a concave border. A convex shape of the AP window reflection is considered abnormal. Abnormal radiographic appearance: The abnormal convexity of the AP window reflection may be due to middle-mediastinum abnormalities such as lymphadenopathy (Fig. 10 on page 19), bronchial artery aneurysms, nerve sheath tumors, bronchopulmonary-foregut malformations or prominent mediastinal fat. 6. Aortic-Pulmonary Stripe Anatomy: The aortic pulmonary stripe represents the interface between the left lung and the mediastinum along the main pulmonary artery toward the aortic arch. This edge runs anteriorly to the AP window reflection. Page 9 of 30

10 Normal radiographic appearance: The aortic pulmonary stripe extends from the aortic arch to the level of the left main bronchus, where it usually continues as the border of the left side of the heart. It delineates the anterior margin of the AP window and is normally straight or slightly convex (Fig. 11 on page 20). Abnormal radiographic appearance: The normal appearance of this interface may be altered by anterior mediastinal disease such as thyroid masses, thymic tumors and lymphadenopathy (Fig. 12 on page 21). 7. Azygoesophageal Recess Anatomy: The azygoesophageal recess represents a mediastinal recess into which the edge of the right lower lobe extends. This space lies anteriorly to the spine, it is limited superiorly by the azygos arch and it extends to the level of the aortic hiatus inferiorly. It is bordered anteriorly by the left atrium and medially by the esophagus and the azygos vein (Fig. 13 on page 22). The interface caused by the right lower lobe outlining the medial limit of the azygoesophageal recess can be appreciated on frontal chest radiographs. Normal radiographic appearance: The azygoesophageal recess is seen on a frontal radiograph as a vertically oriented interface. In its upper third it may be straight or show mild leftward convexity. Right superior convexity may be seen in children and younger adults. The middle third of the recess may be the most variable in the appearance but typically is straight edged or demonstrates mild leftward convexity. In its lower third it usually appears as a straight edge. Abnormal radiographic appearance: Abnormal contour, convexity or disappearance of this interface suggests disease affecting the middle and posterior mediastinal compartments such as lymphadenopathy, bronchopulmonary-foregut malformations, pleural abnormalities, left atrial enlargement, esophageal disease and hiatal hernia (Fig. 14 on page 23, Fig. 15 on page 24). Page 10 of 30

11 8. Paraspinal Lines Anatomy: The paraspinal lines are the interfaces between the lungs and the paraspinous fat and soft tissues. Normal radiographic appearance: th th The right paraspinal line appears straight and runs from the 8 through the 12 thoracic vertebral levels. The left paraspinal line runs vertically from the aortic arch to the diaphragm and lies medial to the paraortic line, although sometimes it can lie lateral to the paraortic line (Fig. 16 on page 25). Abnormal radiographic appearance: The paraspinal lines may be displaced laterally by prominent mediastinal fat or osteophytes. Abnormal contour or displacement may also suggest posterior mediastinal disease such as mediastinal hematoma, mass or extramedullary hematopoiesis (Fig. 17 on page 26). 9. Paraortic line Anatomy: The paraortic line represents the interface formed by the contact of the lateral wall of descending thoracic aorta with the left lower lobe. Normal radiographic appearance: The paraortic line appears as a straight vertical interface, which lies posterior to the cardiac shadow and lateral to the left paraspinal line. In its lower third it comes nearer to the vertebral bodies at the level of the 11 paraspinal line (Fig. 18 on page 27). th thoracic vertebra, overlapping the left Abnormal radiographic appearance: Page 11 of 30

12 An abnormal contour may be the result of different conditions affecting the lung and pleura or the middle and posterior mediastinum, such as lymphadenopathy, aortal aneurysm, gastroesophageal varices and lung neoplasms (Fig. 17 on page 26). Images for this section: Fig. 2: PA chest radiograph (a), cor MPR CT scan (b) and axial CT image (c) demonstrate a normal anterior junction line (arrows). Page 12 of 30

13 Fig. 3: Widening or loss of the anterior junction line may be due to various conditions: (a) axial CT image and cor MPR CT scan demonstrate widening of the line caused by the presence of prominent mediastinal fat (arrows). (b) axial CT image and cor MPR CT scan demonstrate a thymic hyperplasia (arrows) in a patient with thyrotoxicosis. (c) axial CT image and cor MPR CT scan demonstrate a soft tissue mass (arrows) in a patient with lymphoma. Page 13 of 30

14 Fig. 4: Abnormal-appearing anterior junction line in a patient who had undergone right lower lobectomy. PA chest radiograph (a), cor MPR CT scan (b) and axial CT image (c) show the anterior junction line displaced to the right (arrows). Page 14 of 30

15 Fig. 5: PA chest radiograph (a), cor MPR CT scan (b) and axial CT image (c) show a normal posterior junction line (arrows). Page 15 of 30

16 Fig. 6: A 86-year-old patient with lung sarcoma (*) and mediastinal goiter (G). (a) PA chest radiograph shows a mass in the left hemithorax and a madiastinal mass causing deviation of the trachea to the right. The anterior and posterior junction lines are absent, however, the localization of the mediastinal mass within the posterior mediastinum can be inferred from the cervicothoracic sign, as the posterior masses above the level of the clavicles have an interface with lung and therefore typically have sharp, well defined margin (arrows). The anterior mediastinum ends at the level of the clavicles and the anterior masses above this level do not have an interface with lung, thus their margins are usually not sharp. (b) Sag MPR CT scan shows mediastinal goiter (G) in the posterior mediastinum. The retrosternal space (pink arrows) is filled with the enlarged heart and great vessels leaving no space for the anterior apposition of the lungs, which explains the absence of the anterior junction line at radiography. (c) Axial CT image at the level of the clavicles shows mediastinal goiter (G) with obliteration of the posterior junction line and displacement of the trachea (full arrowhead) and esophagus (empty arrowhead). Note the lateral margins of the mass contacting the lungs (arrows) - the CT correlate of the cervicothoracic sign. Ao = ascending aorta, RA = right atrium, LA = left atrium, PA = right pulmonary artery. Page 16 of 30

17 Fig. 7: PA chest radiograph (a), cor MPR CT scan (b,c) and axial CT image (d) show normal right paratracheal stripe (red arrows) and left paratracheal stripe (full arrowhead). In this patient, the left paratracheal stripe on the PA chest radiograph appears as an inconspicuous line that is almost obscured by more prominent pararterial line (empty arrowheads), which is produced by the contact of the lateral margin of the left subclavian artery with the left upper lobe. Note the posterior junction line on the PA chest radiograph (yellow arrow), which is not supposed to be confused with the left paratracheal stripe. Red arrows = the right paratracheal stripe. Full arrowhead = the left paratracheal stripe. Empty arrowheads = the pararterial line. Yellow arrow = posterior junction line. Page 17 of 30

18 Fig. 8: Axial CT images demonstrate examples of different conditions that may cause widening of the paratracheal stripes. (a) Right sided aortic arch (arrow). The empty arrowhead shows the SVC. (b) Azygos continuation of the IVC - the arrow shows enlargement of the azygos vein in the right paratracheal region. The empty arrowhead shows the SVC. (c) Mesothelioma with pleural thickening in the left paratracheal region (arrowhead). (d) Mediastinal goiter in the left paratracheal region (arrowhead). Ao = aorta Page 18 of 30

19 Fig. 9: PA chest radiograph (a), cor MPR CT scan (b) and axial CT image (c) demonstrate a normal-appearing concave AP window reflection (arrow). PA chest radiograph also clearly depicts the AP stripe (interrupted line). Ao = aorta, PA = left pulmonary artery. Page 19 of 30

20 Fig. 10: Abnormal-appearing right paratracheal stripe and AP window reflection in a patient with lymphoma. (a) PA chest radiograph shows widening of the right paratracheal stripe (red arrow) and a convexity of the AP window reflection (white arrow). (b,c) Cor MPR CT scans show soft tissue mass in the right paratracheal region (red arrow) and within the AP window (white arrow). Page 20 of 30

21 Fig. 11: PA chest radiograph (a), cor MPR CT scan (b) and axial CT image (c) demonstrate a normal AP stripe (arrowheads). PA chest radiograph also clearly depicts the AP window as a concave interface (interrupted line). The empty arrowhead on cor MPR CT image shows the auricle of left atrium. Ao = aorta, PA = main pulmonary artery, LV = left ventricle. Page 21 of 30

22 Fig. 12: (a) PA radiograph demonstrates an abnormal appearing AP stripe (arrowhead) in a patient with lymphoma. Cor MPR CT scan (b) and axial CT image (c) demonstrate a soft tissue mass in the anterior mediastinum (arrowheads). Page 22 of 30

23 Fig. 13: (a) PA chest radiograph demonstrates normal appearance of azygoesophageal recess (arrows). (b,d) Cor MPR CT scan and axial CT image show the medial border of the azygoesophageal recess formed by the azygos vein (arrows) and the esophagus (arrow heads). (c) Sag MPR CT image demonstrates the anterior border of azygoesophageal recess formed by the left atrium, superior border formed by the azygos vein (arrows) and posterior border formed by the thoracic spine. AER = azygoesophageal recess, Ao = aorta, RA = right atrium, LA = left atrium, PA - right pulmonary artery. Page 23 of 30

24 Fig. 14: (a) PA chest radiograph shows an abnormal rightward convexity of the lower third of the azygoesophageal recess (arrows). Note the mass, that causes the rightward bulge of the recess, contains an air bubble (arrowhead). Cor MPR CT scan (b) and axial CT image (c) demonstrate a large hiatal hernia as a cause of the abnormal-appearing azygoesophageal recess. Page 24 of 30

25 Fig. 15: An abnormal contour or convexinty of the azygoesophageal line may be due to various conditions: (a) Axial CT image and cor MPR CT scan show thickened esophageal wall (arrows) in a patient with esophageal carcinoma. (b) Axial CT image and cor MPR CT scan show gastroesophageal varices (arrows). (c) Axial CT image and cor MPR CT scan show lymphadenopathy (arrows) and hiatal hernia (*) in a patient with lymphoma. Page 25 of 30

26 Fig. 16: (a) PA chest radiograph shows normal appearance of the paraspinal lines (green arrows = right paraspinal line, green arrowheads = left paraspinal line). Note the paraortic line (interrupted blue line) running laterally to the left paraspinal line in its two upper thirds and overlapping the left paraspinal line in its lower third. Cor MPR CT scan (b) and axial CT images at two different levels (c,d) show the CT correlates of the right paraspinal line (green arrows), the left paraspinal line (green arrowheads) ant the paraortic line (blue arrows). Ao = descending thoracic aorta. Page 26 of 30

27 Fig. 17: A 36-year-old woman with Hodgkin disease. (a) PA chest radiograph shows an inconspicuous opacity (blue arrowheads) with obscuration of the middle third of the paraortic line. Blue arrows show the well defined upper third of the paraortic line. A widening of the paraspinal lines below the level of the diaphragm is also present (green arrows). Cor MPR CT scan (b) and axial CT images at two different levels (c,d) show a lung consolidation abutting the descending aorta (arrowhead) that produces the silhouette sign with the paraortic line on chest radiograph. There is also a destruction of 11th vertebral body with a soft tissue component in the paraspinal region (green arrows), hence the widened paraspinal lines at radiography. Page 27 of 30

28 Fig. 18: (a) PA chest radiograph shows normal appearance of the paraortic line (blue arrows). Note the left paraspinal line (interrupted green line) running medially to the paraortic line in its two upper thirds and overlapping the left paraspinal line in its lower third. Cor MPR CT scan (b) and axial CT images at two different levels (c,d) show the CT correlates of the paraortic line (blue arrows), the right paraspinal line (green arrows) and the left paraspinal line (green arrowheads). Ao = descending thoracic aorta. Page 28 of 30

29 Conclusion Despite the two dimensional representation of mediastinal structures, the PA chest radiograph is a powerful tool in diagnosis of mediastinal diseases and it can be used to localize the detected abnormality in the anterior, middle or posterior mediastinum. It is important for a radiologist to have an understanding of the concept of mediastinal reflections in order to detect an unsuspected mediastinal mass and avoid potential diagnostic mistakes. References 1. Whitten CR, Khan S, Munneke GJ et al. A diagnostic approach to mediastinal abnormalities. Radiographics 2007; 27: Gibbs JM,ChandrasekharCA,FergusonEC,OldhamSAA. Lines and Stripes: Where Did They Go? - From Conventional Radiography to CT. RadioGraphics 2007; 27: Hansell DM, Bankier AA, MacMahon H, McLoud TC, Müller NL, Remy J. Fleischner Society: glossary of terms for thoracic imaging. Radiology 2008, 246(3): Feragalli B, Mantini C, Patea RL, De Filipps F, Di Nicola E, Storno ML. Radiographic evaluation of mediastinal lines as a diagnostic approach to occult or subtle mediastinal abnormalities. Radiol Med. 2011; 116(4): Marano R, Liguori C, Savino G, Merlino B, Natale L, Bonomo L. Cardiac silhouette findings and mediastinal lines and stripes: radiograph and CT scan correlation. Chest. 2011; 139(5): Algin O, Gokalp O, Topal U. Signs in chest imaging. Diagn Interv Radiol 2011;17: Duwe BV, Sterman DH, Musani AI. Tumors of the mediastinum. Chest 2005;128(4): Personal Information MUDr. Nadežda Bystrická, MUDr. Hana poláková, MUDr. Juraj Sýkora Page 29 of 30

30 Department of radiology Národný Onkologický Ústav Klenová 1, Bratislava Slovakia Page 30 of 30