Figure 13b. (a) Axial contrast-enhanced CT scan shows a small amount of fluid in the transverse sinus (T) posterior to the ascending aorta (AA). The transverse sinus extends laterally, where it communicates with the left pulmonic recess (arrow) inferior to the left pulmonary artery. PA = main pulmonary artery. (b) Axial contrast-enhanced CT scan obtained slightly superior to a shows fluid in the left pulmonic recess (arrow). LSV = left superior pulmonary vein, PA = main pulmonary artery, RPA = right pulmonary artery.