Because the images are acquired in a near-isotropic fashion, similar multiplanar reformats to those used in CTA can be produced [39]. In addition to characterizing the extent of aortic pathology and providing precise, highly reproducible aortic measurements, CE-MRA has particular efficacy in delineation of mural thrombus versus intramural blood when CT results are equivocal [10,61]. It is also useful in the differentiation of aortic wall inflammation from intramural hemorrhage and atheroma [36]. A point of caution in the interpretation of MRA is to use source images for measurements, as maximum-intenstiy projection images may obscure the vessel wall and lead to underestimation of lumen size [10]. More advanced magnetic resonance (MR) applications allow flow mapping via time-resolved imaging techniques. Such techniques allow for the evaluation of abnormal vascular anatomy, atherosclerotic plaque burden, collateral blood flow, and hemodynamic parameters in the involved segment of aorta [36,39]. Although CE-MRA is preferred for the aforementioned reasons, certain situations exist in which unenhanced MRA is desirable. These include patients with poor intravenous access; advanced, dialysis-dependent renal failure with glomerular filtration rate <30 mL/min/1.73 m2 (because of the risk of nephrogenic systemic fibrosis); and pregnancy (because of the possible teratogenic effects of gadolinium-based contrast agents) [55,60,62]. Aortography Catheter angiography has largely been replaced by cross-sectional imaging in the evaluation of patients with suspected aortic pathology. An exception is in cases of coexisting malperfusion involving the coronary, visceral, or cerebral circulations. In such cases, angiography allows for evaluation and possible revascularization of the affected vascular bed along with further characterization of aortic pathology [45,61,63].
Thoracic Aortic Aneurysm or Dissection Treatment Planning and Follow Up. Because the images are acquired in a near-isotropic fashion, similar multiplanar reformats to those used in CTA can be produced [39]. In addition to characterizing the extent of aortic pathology and providing precise, highly reproducible aortic measurements, CE-MRA has particular efficacy in delineation of mural thrombus versus intramural blood when CT results are equivocal [10,61]. It is also useful in the differentiation of aortic wall inflammation from intramural hemorrhage and atheroma [36]. A point of caution in the interpretation of MRA is to use source images for measurements, as maximum-intenstiy projection images may obscure the vessel wall and lead to underestimation of lumen size [10]. More advanced magnetic resonance (MR) applications allow flow mapping via time-resolved imaging techniques. Such techniques allow for the evaluation of abnormal vascular anatomy, atherosclerotic plaque burden, collateral blood flow, and hemodynamic parameters in the involved segment of aorta [36,39]. Although CE-MRA is preferred for the aforementioned reasons, certain situations exist in which unenhanced MRA is desirable. These include patients with poor intravenous access; advanced, dialysis-dependent renal failure with glomerular filtration rate <30 mL/min/1.73 m2 (because of the risk of nephrogenic systemic fibrosis); and pregnancy (because of the possible teratogenic effects of gadolinium-based contrast agents) [55,60,62]. Aortography Catheter angiography has largely been replaced by cross-sectional imaging in the evaluation of patients with suspected aortic pathology. An exception is in cases of coexisting malperfusion involving the coronary, visceral, or cerebral circulations. In such cases, angiography allows for evaluation and possible revascularization of the affected vascular bed along with further characterization of aortic pathology [45,61,63].