Thoracic Aorta Interventional Planning and Follow-Up MRA Similar to CT, magnetic resonance imaging (MRI) of the thoracic aorta can be performed with and without intravenous contrast. The principle advantage of MRI over CT is the lack of ionizing radiation, making it a particularly attractive imaging option in young patients. MRI is a more time-consuming study than CT, necessitating a stable patient. Importantly, MRI confers similar sensitivity and specificity as CTA and transesophageal echocardiography (TEE) for detection of dissection flaps, although like TEE it is less accurate for detection of branch vessel involvement [59]. There are a variety of unenhanced MRA techniques, including time of flight, phase-contrast imaging, ECG-gated fast spin-echo, and steady-state free precession (SSFP). SSFP, for example, has been shown to have equal accuracy for the assessment of aortic diameter compared with contrast-enhanced MRA (CE-MRA) [60]. The SSFP technique is also useful for visualization of dissection flaps [39]. General limitations with unenhanced MRA include loss of signal due to turbulent flow, long acquisition times, susceptibility to field inhomogeneity and motion, and the need for considerable patient cooperation for sequences requiring breath holding [36]. CE-MRA using 3-D spoiled gradient-echo sequences is the preferred MRI technique for thoracic aortic imaging, providing superior arterial signal, high spatial and contrast resolution, and rapid data acquisition during a single breath hold [36,39]. ECG gating may be added for motion-free evaluation of the ascending aorta and aortic root. Similar to the typical multiphasic CTA protocol, CE-MRA studies generally consist of unenhanced, arterial, and delayed-phase images. Various triggering methods can be used to ensure adequate gadolinium contrast opacification.
Thoracic Aortic Aneurysm or Dissection Treatment Planning and Follow Up. Thoracic Aorta Interventional Planning and Follow-Up MRA Similar to CT, magnetic resonance imaging (MRI) of the thoracic aorta can be performed with and without intravenous contrast. The principle advantage of MRI over CT is the lack of ionizing radiation, making it a particularly attractive imaging option in young patients. MRI is a more time-consuming study than CT, necessitating a stable patient. Importantly, MRI confers similar sensitivity and specificity as CTA and transesophageal echocardiography (TEE) for detection of dissection flaps, although like TEE it is less accurate for detection of branch vessel involvement [59]. There are a variety of unenhanced MRA techniques, including time of flight, phase-contrast imaging, ECG-gated fast spin-echo, and steady-state free precession (SSFP). SSFP, for example, has been shown to have equal accuracy for the assessment of aortic diameter compared with contrast-enhanced MRA (CE-MRA) [60]. The SSFP technique is also useful for visualization of dissection flaps [39]. General limitations with unenhanced MRA include loss of signal due to turbulent flow, long acquisition times, susceptibility to field inhomogeneity and motion, and the need for considerable patient cooperation for sequences requiring breath holding [36]. CE-MRA using 3-D spoiled gradient-echo sequences is the preferred MRI technique for thoracic aortic imaging, providing superior arterial signal, high spatial and contrast resolution, and rapid data acquisition during a single breath hold [36,39]. ECG gating may be added for motion-free evaluation of the ascending aorta and aortic root. Similar to the typical multiphasic CTA protocol, CE-MRA studies generally consist of unenhanced, arterial, and delayed-phase images. Various triggering methods can be used to ensure adequate gadolinium contrast opacification.