CTA evaluation of thoracic and abdominal aortic aneurysms is very accurate in defining the size and extent of the aneurysm as well as possible involvement of aortic branch vessels. Cross section evaluation of the aortic lumen provides the most accurate measurement of aneurysm diameter of any imaging modality, including catheter angiography. Newer 3-dimensional reconstruction techniques produce images that are similar to catheter angiography and are extremely helpful in giving information regarding aneurysm volume as a means of following aneurysm expansion over time. In addition, these techniques are used increasingly as an aid to surgical or endovascular repair planning as well as for follow-up after repair. CTA is a better tool for evaluating thrombus within the wall of an aneurysm than MRI currently is.
CTA has also become an established technique for the noninvasive evaluation of renal and mesenteric arterial disease. A common indication for renal artery CTA is the workup of renal artery stenosis, a potential cause of hypertension as well as renal insufficiency. In combination with 3-dimensional reformation techniques, CTA is very accurate in detecting renal artery stenosis due to atherosclerosis or fibromuscular dysplasia. CTA can detect accessory renal arteries as well as provide measurement of stenosis, even in relatively small branch vessels. Finally, these techniques can help provide guidance for potential percutaneous therapy.
Similarly, CTA has become an important imaging tool for the evaluation of acute and chronic mesenteric ischemia due to stenosis or occlusion of the mesenteric vessels. In addition, CTA has the advantage of providing information on potential intestinal changes due to disease of the mesenteric vessels. When combined with solid organ imaging (routine CT), CTA can also suggest alternative diagnoses that may mimic mesenteric ischemia in the setting of acute abdominal pain.
Newer, faster scanning techniques have allowed for improvements in longitudinal anatomic coverage. In addition, advances in scan efficiency have improved fine spatial resolution. These factors have allowed more precise visualization and evaluation of smaller branch vessels, including arteries of the lower extremities. CTA is being used more and more for evaluation of arterial runoff in the lower extremities and has become an accepted alternative to conventional angiography. Similarly, CTA can be used to evaluate the carotid arteries and even the smaller arteries in the brain to look for stenoses or small intracranial aneurysms. These methods are becoming important in guiding potential treatment in order to possibly prevent stroke due to a significant carotid artery stenosis or a potentially life- threatening bleed due to an intracranial aneurysm.