CT Angiography of the Thoracic Aorta

The aorta is the largest artery in the human body, pumping up to 200 million liters of blood through the body in an average lifetime. Thoracic aortic disease presentation ranges from asymptomatic (as in an aneurysm incidentally detected on imaging) to severe acute chest pain (as in acute aortic dissection). The recent increased prevalence of aortic disease in western countries is a result of increased clinical awareness and longer life spans. Multidetector-row computed tomography (MDCT) of the aorta can be used to diagnose various acute and chronic conditions of the aorta, including aortic aneurysms, aortic dissections, intramural hematomas, penetrating atherosclerotic ulcers, traumatic injuries, inflammatory disorders, and congenital abnormalities. In the early 1990s, single-detector spiral computed tomography (CT) was introduced into routine clinical imaging, allowing excellent visual assessment of vessels from any angle as opposed to catheter-based projectional angiography. 1–3 However, single-detector spiral CT had limitations, such as long breath holds, motion artifacts from slow gantry rotation time, and limited coverage in z-dimension. 1–3 In the late 1990s, MDCT was introduced. MDCT significantly improved image quality with improved resolution in the z-dimension, faster gantry rotation, increased coverage in the z-dimension, and increased table speed. 4 Modern 64 detector-row and newer-generation CT scanners can evaluate the entire aorta, including its smaller branches, with one short breath hold. Compared with angiography, extravascular structures are also well assessed with MDCT. 4 MDCT provides superior image quality by acquiring isovolumetric subcentimeter voxels, which allow two-dimensional and three-dimensional reconstructions in any orientation. 5 This article reviews the spectrum of MDCT imaging findings in thoracic aortic diseases. Although discussion focuses on the thoracic aorta, initial examination of the aorta should include the entire aorta and iliac arteries; aortic diseases such as aneurysm or dissection frequently affect the whole aorta or may affect multiple regions of the aorta.