J Korean Radiol Soc 1997; 36 : 7?? - 786 Mediastinal Interfaces and Lines : 1 Clinical Significance and Radiographic-CT Correlation Kyung SOO Lee, M.D., Yookyung Kim, M.D. , Boo Kyung Han, M.D. Hye Kyung Yoon, M.D., Dulζ WooRo, Ph.D., Yeon Hyeon Choe, M.D. Hong Sik Byun, M.D., In Wool‘ Choo, M.D., Bokyung Kim Han, M.D. Mediastinal interfaces on a chest radiograph result from contact between medias­ tinal structures and the adjacent lung, while mediastinallines result from contact be­ tween the two lungs across the midline. A variation ofmediastinal interface is medias­ tinal stripe, a narrow band produced by contact ofboth sides of a mediastinal structure with the lungs. Alterations in mediastinal interfaces and lines may be due to variations in normal anatomy, or may reflect the presence of abnormalities within the medias­ tinum. Familiarity with the various normal mediastinal interfaces and lines, and the changes that occur with disease is important for the interpretation of the chest radio­ graph and in the diagnosis of mediastinal abnormalities. The purpose of this pictorial essay is to illustrate the most important normal and abnormal interfaces and lines and also to correlate radiographic and CT findings. Index Words : Mediastinum Mediastinum, abnormalities Mediastinum, CT Mediastinum, radiography Contact of the lung with the various mediastinal structures provides many kinds of mediastinal Mediastinal Li nes interfaces and lines. A chest radiograph, by showing normal and abnormal mediastinal interfaces and lines, AnteriorJunctionalline reflects the anatomic status of a patient mediastinum The anteromedial right and left lungs approach the and gives information on further diagnostic work-up. midline and forms the anterior junctionalline. If the By showing cross-sectional images of the mediastinum lungs do not meet each other closely to form a line, a and lung, CT can visualize and explain the formation of bandlike stripe is formed (Fig. 1). Above and below the normal and abnormal mediastinal interfaces and lines. junctional line, the right and left lungs contact the There are two true mediastinal lines : the anterior retromanubrial anterior mediastinal fat rather than and posterior junction lines; man y kinds of medias­ contralaterallung, thus forming an interface instead of tinal interfaces can be shown on normal and abnormal forming a true line. This interface, above and below chest radiographs. In this exhibit, we will first de­ the true junctionalline was called superior (V-shaped scribe the mediastinal lines, then the mediastinal configuration) and inferior (inverted V-shaped con­ interfaces. Only those mediastinal interfaces that are figuration) recess of anterior junctional reflection by clinically important will be addressed. They will be Proto (2, 3) (Fig. L 2). The interfaces of the superior subdivided into those in the supraazygous, in­ and inferior recess usually shows medial convexity fraazygous, supraaortic and infraaortic areas, as de­ (Fig. 1, 2) scribed by Heitzman et al (1) and will be described in Effacement and distortion of the anterior junctional thatorder. line or lateral convexity ofthe interface ofthe superior and inferior recess suggests the possibility of medias­ IDepartment ofRadiology, Sumsung Medical Center tinal abnormality (Fig. 3). Anterior junctionalline may Re ceived December 26 , 1996; Accepted February 4, 1997 Address reprint requests to: Kyung Soo Lee, M.D. , Department of Radiology, be displaced and visualized prominently when a lobe Samsung Medical Ce nter I 50 Irwon-Dong, Kangnam-Ku, Seo ul 135-230, Korea or lung is atelectatic and contralateral lobe or lung Tel : 82-2-3410-251 L 25 16 FAX: 82-2-3410-2559 herniates through the anterior mediastinum (Fig. 4). - 777 - Kyung Soo Lee, et a/: Mediastinal Interfaces and Lines PosteriorJunctional Li ne Posterior junctional line may be distorted by me­ The posteromedial upper right and left lungs ap­ diastinal disease and especially by esophageal abnor­ proach the midline in front ofthe spine and behind the mality. esophagus to form the posterior junctionalline usually above the azygos and aortic arches (Fig. 2) . As in the Mediastinallnterfaces anterior junctional reflection, the interface, above and below the true junctionalline is called superior and in­ Supraazygous Area ferior recess of posterior junctional reflection. Pos­ Superior Vena Cava Interface terior junctional line rarely forms below the azygos The superior vena cava (SVC) usually indents the lat­ and aortic arch, usually anterior to the esophagus and eral right lung and forms an interface on poserior­ posterior to the descending aorta w hen the postero me­ anterior (PA) radiograph. This interface merges with dial right and left lungs meet each other (2, 4). Air wit­ the border of the right atrium. The great vessels (right hin the lumen of the esophagus along with air in the subclavian artery) ofthe aortic arch become ectatic and posteromediallungs may delineate the esophageal wal­ tortuous as the patients get old, further displacing the ls such that a band-like density denoting esophageal interface laterally. In this case, differentiation of SVC wall may be observed. interface from atelectasis of the right upper lobe and Fig. 1. Chest radiograph demonstrat­ ing anterior junctionalline and rec­ esses (arrows) and posterior junc­ tional line and recesses (arrow­ heads). Anterior junctional line is oblique from right to left whereas posterior junctional line is vertical. Anterior junctionalline is inferior to posterior junctional line which is most frequently seen in supraaortic area. Fig. 2. Chest radiograph showing su­ perior recesses of anterior junctional complex (arrowheads) rather than line. When two superior recesses meet together anteriorly, they form anterior junctionalline (arrows). B Fig. 3. Lateral convexity of superior recess of anterior junctional complex d ue to anterior mediastinal mass. A. Chest radiograph shows widening of superior mediastinum. Lateral convexity of superior recess of anterior junctional complex (arrow) is seen right lateral to sternal shadow (arrowhead). B. Enhanced conventional (lO-mm collimation) CT scan obtained at level of aortic arch demonstrates anterior mediastinal mass (tu berculous lymphadenitis), with lateral displacement of anterior lung 깨 J Korean Radi이 Soc 1997; 36 :777-786 media와 inal abnormality is difficult. Imperceptible tap­ in the right lung and in tracheallumen produces right ering of the interface superior to the clavicle (due to paratracheal stripe. The stripe is usually not more than horizontal course of the innominate vein rather than 4 mm in thickness (1 , 2) vertical at this leveI) and arcuate course ofthe interface Localized thickening of the stripe and change in its on lodortic view are useful signs favoring the diagnosis thickness on serial examinations are important signs of SVC interface (Fig. 5) rather than abnormalities in that indicate abnormalities in paratracheal area (Fig. 6). the right upper lobe or the mediastinum (1) Azygos (Tracheobronchial angle) Node vs. Right Paratracheal Stripe AzygosVein Contact of the tracheal wall (sometimes along with A mass in the right tracheobronchial angle, extend­ areolar tissue, fat and smalllymph nodes) with air both ing cephalad from azygos arch, is usually due to lymph Fig. 4. Lateral displacement ofanterior junctionalline after right lung transplantation. A. Chest radiograph shows right displacement of anterior junctionalline (arrows). Note hyperlucency of native left lung and increased density oftransplanted right lung. B. Thin-section {1. 5-mm 떼coo이에…11lima line (arrow) to 산ttheri핑ghthemi야t산ho야rax. Na따t디ive터hωungi성smo야re hyperlucκcent than transplanted lung. A B c Fig . S. Lateral displacement ofsuperior vena cava interface due to tortuous right innominate artery A. Chest radiograph demonstrates right lateral displacement of superior vena cava interface with lateral convexity (arrows). B. Follow-up lodortic view in same patient shows smooth arc of superior vena cava interface (arrows) heading laterally to axil­ laryarea. c. Enhanced conventional (lO-mm collimation) CT scans obtained at levels of thoracic inlet shows tortuous riQht innominate artery (arrows) which causes displacement ofright innominate vein and superior vena cava (curved arrows) to right side. -779 - Kyung Soo Lee. et a/: Mediastinal Interfaces and Lines Fig. 6. Obliteration ofright paratracheal stripe due to Castleman’ s disease. A. Chest radiograph shows semilunar shaped soft tissue lesion in supraazygos area with obliteration of right paratracheal stnpe. B. Enhanced conventional (lO-mm collima디on) CT scan obtained at level of aortopulmonary window shows highly enhancing mass in pretracheal and retrocaval area, which turned out to be Castleman’s disease A B Fig. 7. Prominent azygos arch due to azygos continuation ofinferior vena cava. A. Chest radiograph shows prominent azygos arch (arrow). This arch extends inferiorly at area of tracheobronchial angle whereas azygos nodes extends superiorly from tracheobronchial angle. Additionally, right paratracheal stripe is clearly visualized superior to azygos arch. B. Tl-weighted (TR/TE; 720/16msec) MR image shows dilated azygos vein (arrows), which was direct1 y connected to inferior vena cava. node enlargement (Fig. 6) whereas a mass beneath the posterior to the esophagus and in front of the spine and arch is due to dilated azygos arch (Fig. 7) (1 , 2) . In ad­ the ascending portion of the azygos vein (5 , 6). It is dition, azygos arch is always situated