The complete diagnostic evaluation of the thoracic aorta requires visualization of the lumen, aortic wall, and periaortic region in order to define intraluminal, mural, and extramural pathology. Imaging modalities must be capable of evaluating the entire extent of the aorta and the origin of the arch vessels in order to define the extent of any abnormality. In some instances the status of the aortic valve and the annulus must also be evaluated. Well-established and accepted methods for examining the thoracic aorta include conventional catheter angiography, contrast-enhanced computed tomography (CT), and transthoracic or transesophageal echocardiography. Cardiac and aortic angiography for the diagnosis of diseases of the heart and the great vessels has been substantially replaced in recent years by noninvasive imaging techniques. The major noninvasive technique is echocardiography. During the past decade CT and magnetic resonance imaging (MRI) have also been used for the diagnosis of acquired and congenital diseases of the heart and the thoracic aorta. Particularly when currently developed helical CT technology is applied, this method is able to provide images of the thoracic aorta similar to a traditional angiogram in three-dimensional reconstructions.