Figure 1. Normal anatomy of the thoracic inlet. Axial contrast material-enhanced CT scan obtained at the level of the thyroid gland shows the anterior jugular vein (aj), anterior scalene muscle (as), biceps muscle (b), common carotid artery (cc), internal jugular vein (ij), long muscle of the neck (lc), levator muscle of the scapula (ls), middle scalene muscle (ms), greater pectoral muscle (p), sternocleidomastoid muscle (sc), trachea (t), and trapezius muscle (tp).