Normal thoracic aorta and aneurysm on CT scan

A CT scan at the level of the main pulmonary artery (A) shows a normal ascending aorta (dashed arrow), which is about the same size as the pulmonary artery (arrow). Image B shows an aneurysm of the ascending aorta (dashed arrow), which is much larger than the main pulmonary artery (arrow). The descending aorta shows early enlargement and atherosclerosis in the wall (arrowhead).