In cases of proximal thoracic aorta pathology, electrocardiography (ECG) gating can help achieve motion-free images along with ideal contrast enhancement. Acquisition of thin-section (0.5 to 2.0 mm) axial images with subsequent reconstruction of multiplanar reformats, maximum-intensity projections, curved planar reformats, and volume-rendered images allows for precise assessment of aortic anatomy [10,26]. Centerline or double oblique measurements are critical to avoid errors based on aortic obliquity; such measurements are easily obtained with modern postprocessing software [40]. More advanced postprocessing techniques such as 3-D virtual angioscopy, which affords a virtual endoluminal view, have shown utility in the surgical planning period [41]. Because thoracic aorta pathology often extends to involve the abdominal aorta, imaging of the chest, abdomen, and pelvis is standard in evaluation of vascular pathology. CTA can also identify higher-risk features and findings that may predict higher rates of postintervention complications. For example, it has been shown that increasing aortic tortuosity, which can be expressed as index values based on CTA measurements, is associated with increased risk of endoleak, stroke, and reduced survival after TEVAR for thoracic aortic aneurysm [42,43]. In patients with acute aortic dissection, the presence of a single entry, as opposed to multiple sites, is associated with higher aortic growth rates, possibly because of deranged inflow and outflow dynamics; CTA has been shown to reliably detect entry tears with 82% sensitivity and 100% specificity [44]. When abdominal visceral branches are involved and there is potential for celiac trunk or superior mesenteric artery coverage by the stent graft, CTA can help determine the presence of collateral vessels [45]. In the absence of collaterals, an open surgical or hybrid approach may be necessary to avoid visceral ischemia.
Thoracic Aortic Aneurysm or Dissection Treatment Planning and Follow Up. In cases of proximal thoracic aorta pathology, electrocardiography (ECG) gating can help achieve motion-free images along with ideal contrast enhancement. Acquisition of thin-section (0.5 to 2.0 mm) axial images with subsequent reconstruction of multiplanar reformats, maximum-intensity projections, curved planar reformats, and volume-rendered images allows for precise assessment of aortic anatomy [10,26]. Centerline or double oblique measurements are critical to avoid errors based on aortic obliquity; such measurements are easily obtained with modern postprocessing software [40]. More advanced postprocessing techniques such as 3-D virtual angioscopy, which affords a virtual endoluminal view, have shown utility in the surgical planning period [41]. Because thoracic aorta pathology often extends to involve the abdominal aorta, imaging of the chest, abdomen, and pelvis is standard in evaluation of vascular pathology. CTA can also identify higher-risk features and findings that may predict higher rates of postintervention complications. For example, it has been shown that increasing aortic tortuosity, which can be expressed as index values based on CTA measurements, is associated with increased risk of endoleak, stroke, and reduced survival after TEVAR for thoracic aortic aneurysm [42,43]. In patients with acute aortic dissection, the presence of a single entry, as opposed to multiple sites, is associated with higher aortic growth rates, possibly because of deranged inflow and outflow dynamics; CTA has been shown to reliably detect entry tears with 82% sensitivity and 100% specificity [44]. When abdominal visceral branches are involved and there is potential for celiac trunk or superior mesenteric artery coverage by the stent graft, CTA can help determine the presence of collateral vessels [45]. In the absence of collaterals, an open surgical or hybrid approach may be necessary to avoid visceral ischemia.