Imaging description

Acute thoracic aortic dissection is the most common aortic catastrophe. It is caused by a tear along the laminar planes of the media layer of the aortic wall, with formation of a blood-filled channel. The diagnosis of aortic dissection is usually quite simple using contrast-enhanced multi-detector CT angiography (CTA). However, several artifacts can simulate aortic dissection.

Most artifacts lead to a false-positive diagnosis.

Pulsation artifact mimics aortic dissection, particularly Stanford type A aortic dissection. Within the ascending aorta, pulsation artifact occurs principally in the left anterior and right posterior wall of the ascending aorta. To discriminate, look for the artifact extending into the adjacent mediastinal fat, and similar “pseudoflaps” in the adjacent superior vena cava and main pulmonary artery. This can be particularly valuable to discriminate between type A and type B aortic dissection, and can even be performed using prospective gating without beta blockade in the acutely unwell patient (Figure 44.1). Aortic pulsation artifact can obscure subtle intimal irregularities, and impairs assessment of aortic valve and coronary involvement for type A dissections. These relationships are well assessed with gating (Figure 44.2) [1].