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Journal of Bronchology & Interventional Pulmonology:
doi: 10.1097/LBR.0b013e318207e6d5
Tools and Techniques

Standard Techniques of Imaging of IASLC Borders by Endoscopic Ultrasound

Sharma, Malay MD, DM; Rameshbabu, Chittapuram Srinivasan Msc; Mohan, Pazhanivel MD, DM

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Department of Gastroenterology, Jaswant Rai Specialty Hospital, Meerut, Uttar Pradesh, India

Supported by none.

There is no conflict of interest.

Supplemental Digital Content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's Website, www.bronchology.com.

Reprints: Malay Sharma, MD, DM, Department of Gastroenterology, Jaswant Rai Specialty hospital, Meerut, Uttar Pradesh 250 001 India (e-mail: sharmamalay@hotmail.com).

Received October 30, 2010

Accepted November 22, 2010

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Abstract

Linear endoscopic ultrasound is useful in the diagnosis and staging of non-small cell lung cancer. Endoscopic ultrasound has been proposed as the first test to be used, before bronchoscopy, for staging of lung cancer. The International Association for the Study of Lung Cancer has redefined the anatomic borders of lymph node stations. We describe the techniques of linear endoscopic ultrasound for mapping of the lymph nodes as defined by the International Association for the Study of Lung Cancer classification.

Linear endoscopic ultrasound is useful in the diagnosis and staging of non-small cell lung cancer.1–3 Endoscopic ultrasound (EUS) has been proposed as the first test to be used, before bronchoscopy, for staging of lung cancer.4 The International Association for the Study of Lung Cancer (IASLC) has recently redefined the anatomic borders of lymph node stations.5 We describe the techniques of linear EUS for mapping of the lymph nodes as defined by IASLC classification.

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TECHNIQUES

Imaging of mediastinum is carried out by 360-degree rotation of the endoscope from 6 positions. The position is changed by pushing in or pulling out by approximately 3 cm at a time. At each position a home base is identified (Home base is a structure easily found by manipulation of the scope if orientation is lost during imaging). The mediastinum is examined from each position by rotating the scope by 180 to 360 degrees (Fig. 1, see Supplemental Digital Content in video 1, Supplemental Digital Content 1, http://links.lww.com/LBR/A56, which shows EUS examination from 6 positions in the mediastinum). For uniform description, structures are described while making a clockwise movement from each position. Important centimeter landmarks are shown (Fig. 2). A cranial part of image to right and caudal part of image to left convention is followed in 3 steps (Fig. 3A).

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(A) Identify home base

(B) Identify anatomic landmarks

(C) Identify IASLC borders

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Position 1: Cervical Esophagus
A. Identify Home Base

The thyroid gland can act as the home base in this position, but it is difficult to stabilize the scope in the cervical esophagus and initially the aortic arch is identified as the home base. The thyroid gland lies anterior to the esophagus from the lower border of the cricoid cartilage to the manubrium sterni. The thyroid gland is identified by pulling the scope into the upper esophagus after identifying the aortic arch. The aortic arch is identified at 23 cm by clockwise rotation from a maximally rotated anticlockwise position as a circular (1.5 to 2.0 cm) anechoic vascular structure (Fig. 3A).

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B. Identify Anatomic Landmarks

Slight clockwise rotation shows the left common carotid artery and left internal jugular vein beyond the left lobe of the thyroid gland. In general, the venous system is larger and lies more laterally beyond the arteries of the neck. Clockwise rotation to 180 degrees from this position may show the right common carotid artery and right internal jugular vein (Fig. 3B, C, see Supplemental Digital Content in video 2, Supplemental Digital Content 2, http://links.lww.com/LBR/A57 and video 3, Supplemental Digital Content 3, http://links.lww.com/LBR/A58. Video 2 shows the origin of the left common carotid artery, and part of the thyroid gland and parathyroid gland. Video 3 shows the thyroid gland and left internal jugular vein).

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C. Identify IASLC Borders

The upper border of the thyroid gland corresponds to the cricoid cartilage (upper border of station 1), and the lower border of the thyroid gland corresponds to the upper border of the manubrium sterni (lower border of station 1 and upper border of station 2L). The evaluation of lymph nodes of station 1 is often better accomplished by ultrasound examination of the neck (Fig. 3D, see Supplemental Digital Content in video 4, Supplemental Digital Content 4, http://links.lww.com/LBR/A59, which shows an external ultrasound from the neck. The thyroid gland and a lymph node of station 1 are observed lateral to the thyroid gland between the left common carotid artery and left internal jugular vein).

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Position 2: Upper Esophagus Superior to the Arch of the Aorta
A. Identify Home Base

Aortic arch is identified.

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B. Identify Anatomic Landmarks

The scope is pulled up 2 cm above the aortic arch. Clockwise rotation from the left lateral wall of the esophagus shows the left subclavian artery, the left common carotid artery, and occasionally the brachiocephalic trunk coming from the top of the arch of the aorta. The left brachiocephalic vein crosses anterior to all 3 arteries to join the right brachiocephalic vein and form the superior vena cava. The lymph nodes of 2R lie posterior to the great vessels of the neck, whereas the lymph nodes of 3a lie anterior to the great vessels of the neck. (Fig. 4, Figs. 5A, B, see Supplemental Digital Content in video 5, Supplemental Digital Content 5, http://links.lww.com/LBR/A60; video 6, Supplemental Digital Content 6, http://links.lww.com/LBR/A61; and video 7, Supplemental Digital Content 7, http://links.lww.com/LBR/A62. Video 5 shows the left subclavian artery taking origin from the top of the arch of the aorta, video 6 shows the brachiocephalic trunk taking origin from the arch of the aorta, and video 7 shows the mediastinal structures during rotation from the second position).

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C. Identify IASLC Borders

Important borders are the apex of the lungs, the upper border of the manubrium sterni, and the upper border of the clavicle. The manubrium sterni and clavicle are not observed by EUS. The apex of the lungs can be identified with some approximation (Fig. 5A, Fig. 6). Lymph nodes of stations 2, 3a, and 3p are observed in this area (Fig. 3C, Figs. 4, 7, see Supplemental Digital Content in video 8, Supplemental Digital Content 8, http://links.lww.com/LBR/A63, which shows the aortic arch, the union of the left internal jugular vein with the left subclavian vein to form the brachiocephalic vein, and a lymph node of station 3a).

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Position 3: Upper Esophagus in the Arches Area
A. Identify Home Base

Two important home bases are the aortic arch and azygos vein arch at a distance of 23 to 25 cm. The azygos vein appears as a thin, longitudinal, echo-poor structure adjacent to the middle part of the esophageal wall. The presence of indentation owing to the posterior intercostal arteries along the posterior border of the AV and the presence of numerous intercostal veins joining the lateral border of AV help in additional characterization of the azygos vein. The azygos vein can also be located by rotating approximately 45 degrees in an anticlockwise direction from the descending aorta. (Fig. 8, see Supplemental Digital Content in video 9, Supplemental Digital Content 9, http://links.lww.com/LBR/A66; video 10, Supplemental Digital Content 10, http://links.lww.com/LBR/A67; and video 11, Supplemental Digital Content 11, http://links.lww.com/LBR/A64. Video 9 shows posterior intercostal arteries taking origin from the aorta and going behind the azygos vein. Video 10 shows the descending aorta as it is traced up as a large tubular structure forming a bright deep interface with the left lung. Video 11 shows structures on clockwise rotation from the descending aorta).

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B. Identify Anatomic Landmarks

The descending aorta is identified (Fig. 9A). The azygos vein is traced cranially as it forms an arch and disappears from view by moving away from the transducer toward the superior vena cava at 25 cm (Figs. 9B, C).

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C. Identify IASLC Borders

Important borders are the upper and lower border of the aortic arch and the lower border of the azygos vein (Fig. 3A, Fig. 9C). Lymph nodes of station 4L and 6 are observed in this area (Fig. 8, Figs. 10A, B).

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Position 4: Middle Esophagus Below the Aortic Arch
A. Identify Home Base

The mediastinal structures during rotation from the fourth position show an area below the arch that consists of 2 spaces: the aortopulmonary window and the subcarinal window (Figs. 11, 12). These spaces can be evaluated by clockwise and anticlockwise rotation. Clockwise rotation shows the course of the right pulmonary artery for a distance of approximately 3 cm as it goes into the right lung and divides into 2 branches after crossing the intermediate bronchus. Important home base structures lie in the ventral (anterior) and dorsal (posterior) positions to the esophagus (Fig. 2, see Supplemental Digital Content in video 12, Supplemental Digital Content 12, http://links.lww.com/LBR/A65, which shows the subcarinal window).

Figure 11
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Figure 12
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B. Identify Anatomic Landmarks

The descending aorta creates bright echoes owing to interface with the left lung. The right pulmonary artery lies anterior to the left atrium and esophagus (Fig. 13A).

Figure 13
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C. Identify IASLC Borders

The important borders are the lower border of the aortic arch, the upper border of the left pulmonary artery, the lower end of the trachea, the lower border of the right main bronchus, the lower border of the intermediate bronchus, and the lower border of the left main bronchus (Fig. 12). The upper border of the right pulmonary artery where it sends a branch to the upper lobe (truncus anterior) corresponds to the lower border of the right main bronchus (Fig. 13B).9,10 The upper border of the right pulmonary artery at the point of this division corresponds to the lower border of the right main bronchus and the lower limit of station 10R. The area between the right superior and inferior pulmonary veins corresponds to the lower border of the intermediate bronchus (Fig. 2). The upper border of the left superior pulmonary vein corresponds to the lower limit of the left bronchus (Fig. 2).10 The aortopulmonary window is identified below the aortic arch (Fig 13C, D, see Supplemental Digital Content video 13, Supplemental Digital Content 13, http://links.lww.com/LBR/A68, which shows the aortic arch, the right pulmonary artery, the right main bronchus, and the intermediate bronchus).7

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Position 5: Lower Esophagus Below the Subcarinal Area
A. Identify Home Base

The descending aorta, the azygos vein, and the left atrium are important home bases. The left atrium is an important vascular landmark, which is identified as a large pulsatile chamber at 33 cm with the mitral valve opening into the deeper left ventricle. On clockwise rotation past the left atrium, the scanning plane sweeps from anterior to posterior along the right esophageal wall, where it visualizes the right lung, the azygos vein, and finally the spine. With clockwise rotation and withdrawal, the aortic outflow tract, aortic valve, and ascending aorta can be visualized through the left atrium. Further clockwise rotation will show the superior vena cava, which can be followed down to the right atrium and sometimes to the inferior vena cava. (See Supplemental Digital Content in video 14, Supplemental Digital Content 14, http://links.lww.com/LBR/A69, which shows the mediastinal structures during rotation from the fifth position).

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B. Identify Anatomic Landmarks

The left atrium is followed into the left ventricular outflow tract and the right pulmonary artery is followed into the right ventricular outflow tract.6,11,12 Once the left atrium is visualized, generally clockwise rotation shows the right-sided outflow tract, and slight anticlockwise rotation shows the left ventricular outflow tract. From the left atrium, the left ventricular outflow tract, and from the pulmonary artery the right ventricular outflow tract can be followed (see Supplemental Digital Content in video11, Supplemental Digital Content 11, http://links.lww.com/LBR/A64 and video 15, Supplemental Digital Content 15, http://links.lww.com/LBR/A70. Video 15 shows the mediastinal structures during rotation from the fifth position). Clockwise rotation to 180 degrees will show the descending aorta (Fig. 14). The lower border of the right inferior pulmonary vein corresponds to the upper limit of the pulmonary ligament (Fig. 15A). Lymph nodes of the pulmonary ligament (station 9) lie caudal to the plane below the pulmonary veins. The diaphragm forms the lower limit of station 8 (Fig. 15B, see Supplemental Digital Content in video 16, Supplemental Digital Content 16, http://links.lww.com/LBR/A71, which shows the right inferior pulmonary vein going anterior to the esophagus. The lymph node lying just below the right inferior pulmonary vein lies in the pulmonary ligament and belongs to station 9).

Figure 14
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Figure 15
Figure 15
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C. Identify IASLC borders

The lower border of the inferior pulmonary veins and upper border of the diaphragm are important borders. The lymph nodes of stations 8, 9, and 11i lie in this area.

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Position 6: Lower Esophagus Below Diaphragm

The area below the diaphragm is not included in IASLC classification (Fig. 9A).

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Other IASLC Borders

Above the manubrium sterni and below the carina the midline defines the border between the right and left side. Between the manubrium sterni and the carina; the left lateral wall of the trachea defines left and right. The area posteriorly between the right and left tracheal border contains station 3p lymph nodes (Fig. 5).

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CONCLUSION

The practical knowledge of EUS is useful for mapping of lymph nodes.

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ACKNOWLEDGMENT

The authors acknowledge the contribution of Mr Pran Prakash for creating the illustrations and animation videos.

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REFERENCES

1. Puli SR, Batapati Krishna Reddy J, Bechtold ML, et al. Endoscopic ultrasound: it's accuracy in evaluating mediastinal lymphadenopathy? A meta-analysis and systematic review World J Gastroenterol.. 2008;14:3028–3037

2. Micames CG, McCrory DC, Pavey DA, et al. Endoscopic ultrasound-guided fine-needle aspiration for non-small cell lung cancer staging: a systematic review and metaanalysis Chest.. 2007;131:539–548

3. Tournoy KG, Ryck FD, Vanwalleghem L, et al. The yield of endoscopic ultrasound in lung cancer staging: does lymph node size matter? J Thorac Oncol.. 2008;3:245–249

4. Singh P, Camazine B, Jadhav Y, et al. Endoscopic ultrasound as a first test for diagnosis and staging of lung cancer: a prospective study Am J Respir Crit Care Med.. 2007;175:345–354

5. Rusch VW, Asamura H, Watanabe H, et al. The IASLC Lung Cancer Staging Project: a proposal for a new International lymph node map in the forthcoming seventh edition of the TNM classification for lung cancer J Thorac Oncol.. 2009;4:568–577

6. Deprez PH. Choice of endosonographic equipment and normal endosonographic anatomy Best Pract Res Clin Gastroenterol.. 2009;23:623–627

7. McComb BL. Reflecting upon the left superior mediastinum J Thorac Imaging.. 2001;16:56–64

8. Herth FJ, Eberhardt R, Krasnik M, et al. Endobronchial ultrasound guided transbronchial aspiration of lymph nodes in the radiologically and positron emission tomography normal –mediastinum in patients with lung cancer Chest.. 2008;133:887–891

9. Sussmann AR, Ko JP. Understanding chest radiographic anatomy with MDCT reformations Clin Radiol.. 2010;65:155–166 [Epub December 16, 2009].

10. Roose C, Rosse PG Hollinshead's Textbook of Anatomy. 19975th ed Philadelphia Lippincott-Raven:450–451

11. Bhatia V. Endoscopic ultrasound: imaging techniques and applications in the mediastinum Trop Gastroenterol.. 2010;30(2 suppl):S4–S19

12. Sharma M, Arya CL, Somasundaram A, et al. Techniques of linear endobronchial ultrasound imaging J Bronchol Intervent Pulmonal.. 2010;17:177–187

Keywords:

endoscopic ultrasound; lymph node; IASLC borders

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© 2011 Lippincott Williams & Wilkins, Inc.

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