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Figure 2.7 Radial array image at the mid aortic arch.

More proximally from the area at the AP window the aorta elongates and forms the aortic arch (Figure 2.7). This usually creates a semicircle on the entire right side of the image correlating to the left‐sided arch. However, with usual orientation the aorta should not cross the midline. The left carotid and left subclavian artery can easily be seen to leave the aortic arch as small round structures on the right side of the image (Figure 2.8). The brachiocephalic artery can sometimes be seen as well superior to the carotid on the right. As the scope is withdrawn the thyroid comes into view. For example, on the right of Figure 2.9 a prominent thyroid can be seen with a cystic structure within it.

Normal linear thoracic anatomy

The linear scope is advanced to the GE junction by following the descending aorta from the level of the arch downward (Figure 2.10). In order to follow this path, the scope is usually torqued clockwise 90–180 degrees and, as the aorta is followed down, the scope is gently rotated counterclockwise to stay on the aorta. As seen in Video 2.2, the thyroid is visualized briefly and the scope is then advanced to the level of the GE junction.

Figure 2.8 Radial array image at the level of the left carotid and subclavian arteries.

Figure 2.9 Radial array image at the level of the thyroid.

The origin of the celiac artery (Figure 2.11) is identified and then the scope can be withdrawn. This is the standard reference point for the beginning of the exam during withdrawal. Examination of the extraesophageal and thoracic structures is more time consuming than the radial approach as this echoendoscope’s narrow focal point has to be torqued back a further 180 degrees to cover the same field of examination. This is done by withdrawing the scope at increments with constant back and forth torque.

As the scope is withdrawn 3–5 cm back from the GE junction, the scope will need to be rotated 180 degrees off the aorta to see the left atrium and cardiac structures. The cardiac structure can be discerned quite readily using the linear scope. The mitral valve is just adjacent to the aortic root, which is just at clockwise rotation from the mitral valve. The aortic valve can be visualized at various angles with appropriate endoscopic manipulation given its position relative to the esophagus (Figure 2.12).

Figure 2.10 Linear array image at the mid aorta.

Figure 2.11 Linear array image at the level of the celiac artery.

      Withdrawing from the level of the left atrium by 1–2 cm reveals the subcarinal space. This is the area between the pulmonary artery and the left atrium. The bifurcation of the trachea by definition occurs at this level as well.

The AP window is just proximal to this area by several centimeters’ orientation and is slightly clockwise torque from the subcarinal space. The space between the aortic arch and the pulmonary artery make up this region. This is below the level of the aortic arch by a few centimeters. There is a small node seen on the image which could be readily sampled via endoscopic ultrasound‐guided fine needle aspiration (EUS‐FNA) (Figure 2.13).

Figure 2.12 Linear array image at the aortic root.

Figure 2.13 Linear array image at the aortopulmonary window (APW). PA, pulmonary artery.

      The azygos arch is also visualized around this area, just at or slightly below the aortic arch. The azygos vein can be followed distally along the spine, as in the accompanying Video 2.2. Occasionally intercostal veins are visible.

      Chapter video clips

Video 2.1 Radial array examination of the extraesophageal spaces.

Video 2.2 Linear array examination of the extraesophageal spaces.

3 Normal Mediastinal Anatomy by EUS and EBUS

       Juan Corral1, Sebastian Fernandez‐Bussy2, and Michael B. Wallace1

      ¹ Division of Gastroenterology and Hepatology, Mayo Clinic College of Medicine, Jacksonville, FL, USA

      ² Division of Pulmonary Medicine and Critical Care, Mayo Clinic College of Medicine, Jacksonville, FL, USA

Introduction

      The mediastinum is a common anatomical location for lymph node (LN) metastases in lung cancer as well as many other malignant and inflammatory conditions. The presence and specific location of mediastinal LN metastases in non‐small cell lung cancer (NSCLC) dictates therapy with surgery for localized disease, combination therapy when

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