MRA without IV contrast can also be used to create geometric models for computational flow dynamics [99]. Additionally, 4-D flow MRI sequences can be obtained [99]. These sequences are the acquisition of 3-D phase-contrast images in a time-resolved, ECG-gated manner with 3-D velocity encoding. Both computational flow dynamics and 4-D flow MRI can be used to examine hemodynamic information in thoracic aortic aneurysms, such as wall shear stress, flow patterns, and helical flow that may help to identify patients at risk for rupture [99]. For aortic atherosclerotic disease, both MRA without IV contrast and MRA without and with IV contrast can be used to collect physiologic information about aortic flow in order to provide an assessment of aortic wall stiffness and to generate 4-D flow MRI [42,99]. One disadvantage of MRI of the chest and abdomen without and with IV is that it may underestimate the thickness of atherosclerotic plaques compared with other modalities [108]. One advantage of MRI of the chest and abdomen is that it can be used to evaluate the composition of atherosclerotic plaques for lipids, fibrosis, calcifications, and intraplaque hemorrhage [95,109]. Because of improved visualization and decreased acquisition times, the use of IV contrast for MRA of the chest and abdomen is preferred, but sufficient information can also be obtained without the use of IV contrast [100-104,110]. Radiography Chest The chest radiograph is a helpful initial imaging evaluation for the diagnosis of degenerative aortic disease, especially if an acute complication is suspected. However, because of the lack of sensitivity in assessing the extent of disease [35], more definitive tests are required. Regarding atherosclerotic aortic disease, some studies have used lateral lumbar radiographs to both quantify and correlate atherosclerotic disease in the aorta to bone mineral density Nontraumatic Aortic Disease [111], patient diet [112], and more generalized atherosclerotic disease [113].
Nontraumatic Aortic Disease. MRA without IV contrast can also be used to create geometric models for computational flow dynamics [99]. Additionally, 4-D flow MRI sequences can be obtained [99]. These sequences are the acquisition of 3-D phase-contrast images in a time-resolved, ECG-gated manner with 3-D velocity encoding. Both computational flow dynamics and 4-D flow MRI can be used to examine hemodynamic information in thoracic aortic aneurysms, such as wall shear stress, flow patterns, and helical flow that may help to identify patients at risk for rupture [99]. For aortic atherosclerotic disease, both MRA without IV contrast and MRA without and with IV contrast can be used to collect physiologic information about aortic flow in order to provide an assessment of aortic wall stiffness and to generate 4-D flow MRI [42,99]. One disadvantage of MRI of the chest and abdomen without and with IV is that it may underestimate the thickness of atherosclerotic plaques compared with other modalities [108]. One advantage of MRI of the chest and abdomen is that it can be used to evaluate the composition of atherosclerotic plaques for lipids, fibrosis, calcifications, and intraplaque hemorrhage [95,109]. Because of improved visualization and decreased acquisition times, the use of IV contrast for MRA of the chest and abdomen is preferred, but sufficient information can also be obtained without the use of IV contrast [100-104,110]. Radiography Chest The chest radiograph is a helpful initial imaging evaluation for the diagnosis of degenerative aortic disease, especially if an acute complication is suspected. However, because of the lack of sensitivity in assessing the extent of disease [35], more definitive tests are required. Regarding atherosclerotic aortic disease, some studies have used lateral lumbar radiographs to both quantify and correlate atherosclerotic disease in the aorta to bone mineral density Nontraumatic Aortic Disease [111], patient diet [112], and more generalized atherosclerotic disease [113].