Potential nephrotoxicity from iodinated contrast in patients with impaired renal function is the primary concern in this patient population, although the benefits of obtaining key diagnostic information typically outweigh the low risk of developing contrast-induced nephropathy [55]. Utilization of modern CT optimization techniques, such as high-pitch spiral CT imaging, low kilovolt (peak) imaging, wide-area detectors, and iterative reconstruction techniques, allows for lower volumes of contrast and lower radiation dose with adequate diagnostic image quality [39,56,57]. CT CT Unenhanced CT is useful for identification of aortic size, acute IMH, and aortic calcification. In conjunction with CTA, sensitivity for detection of IMH is as high as 96%, and sensitivity and specificity for detection of the intimal flap in aortic dissection approach 100% [11,39]. Moreover, unenhanced CT can delineate complications related to acute aortic syndromes such as mediastinal or pericardial hemorrhage and rupture. The addition of CTA allows for comprehensive assessment of other sequelae, including end-organ ischemia, acute aortic valvular insufficiency, intravascular thrombus, and supra-aortic, coronary, and mesenteric vascular involvement [25,39,58]. The use of contrast-enhanced CT and multiphase CT (without and with contrast) can provide similar information to CTA with regard to the anatomic extent of vascular pathology. Often, such studies are pursued to investigate other clinical questions or vague presentations and incidentally reveal significant vascular findings in the thoracic aorta. The lack of standard thin-section image acquisition, arterial-phase bolus timing, and 3-D renderings with these techniques is the principal limitation, and therefore CTA is the preferred imaging modality for the dedicated workup of thoracic aorta diseases [37,39].
Thoracic Aortic Aneurysm or Dissection Treatment Planning and Follow Up. Potential nephrotoxicity from iodinated contrast in patients with impaired renal function is the primary concern in this patient population, although the benefits of obtaining key diagnostic information typically outweigh the low risk of developing contrast-induced nephropathy [55]. Utilization of modern CT optimization techniques, such as high-pitch spiral CT imaging, low kilovolt (peak) imaging, wide-area detectors, and iterative reconstruction techniques, allows for lower volumes of contrast and lower radiation dose with adequate diagnostic image quality [39,56,57]. CT CT Unenhanced CT is useful for identification of aortic size, acute IMH, and aortic calcification. In conjunction with CTA, sensitivity for detection of IMH is as high as 96%, and sensitivity and specificity for detection of the intimal flap in aortic dissection approach 100% [11,39]. Moreover, unenhanced CT can delineate complications related to acute aortic syndromes such as mediastinal or pericardial hemorrhage and rupture. The addition of CTA allows for comprehensive assessment of other sequelae, including end-organ ischemia, acute aortic valvular insufficiency, intravascular thrombus, and supra-aortic, coronary, and mesenteric vascular involvement [25,39,58]. The use of contrast-enhanced CT and multiphase CT (without and with contrast) can provide similar information to CTA with regard to the anatomic extent of vascular pathology. Often, such studies are pursued to investigate other clinical questions or vague presentations and incidentally reveal significant vascular findings in the thoracic aorta. The lack of standard thin-section image acquisition, arterial-phase bolus timing, and 3-D renderings with these techniques is the principal limitation, and therefore CTA is the preferred imaging modality for the dedicated workup of thoracic aorta diseases [37,39].