Normal imaging appearance of the aorta on CT and MRI

What is the normal imaging appearance of the aorta on computed tomography (CT) and magnetic resonance imaging (MRI)?

The normal aorta on imaging can be divided into the following five parts: the aortic root, the ascending aorta, the proximal (anterior) aortic arch, the distal (posterior) aortic arch, and the descending thoracic aorta. The proximal segment of the ascending aorta is the aortic root, which begins at the upper part of the left ventricle and is approximately 3 cm in diameter in adults. The aortic root and most of the ascending aorta (approximately 5 cm long) is contained within the pericardium. The aortic root has three cusps, which define three spaces called the sinuses of Valsalva: the right, left, and noncoronary sinuses. The right coronary artery normally arises from the right cusp, and the left coronary artery arises from the left cusp. The ascending aorta is located along the right mediastinal border and becomes the aortic arch at the origin of the innominate artery. The aortic arch also gives rise to the left common carotid and left subclavian arteries.

The descending aorta begins where the aortic arch ends, immediately beyond the origin of the left subclavian artery. The aorta descends within the thorax adjacent to the vertebral column after crossing superiorly and then posteriorly over the root of the left lung. After crossing the diaphragmatic hiatus, it becomes the abdominal aorta, which is approximately 2 cm in diameter. Eventually, the abdominal aorta ends by dividing into right and left common iliac arteries, slightly to the left of the midplane at the lower border of the fourth lumbar vertebra. The descending aorta is the most posterior structure adjacent to the spine.

On CT or MRI, the normal aortic lumen will appear round in cross-section with a thin wall.

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