Evaluation of dissections and aneurysms of the thoracic aorta by conventional and dynamic CT scanning.

Conventional computed tomography (CT) with intravenous contrast injection effectively demonstrates the features of aneurysms of the thoracic aorta (dilatation, calcification, intraluminal thrombus, and displacement and erosion of adjacent structures). In aortic dissection, CT can establish the diagnosis by demonstrating (a) double channels with an intimal flap or (b) displaced intimal calcifications if one channel is thrombosed. Dynamic CT following a contrast bolus shows the relative rate of filling of the true and false channels and demonstrates the intimal flap with optimum clarity. Reformatted CT images (paraxial and oblique) display the entire thoracic aorta in the plane of the arch, resembling an aortogram. CT is noninvasive and can be easily repeated to assess progress. Although aortography is still required prior to surgery in some cases, CT is a safe screening procedure that may avoid some invasive angiographic procedures.