Similar to CTA, MRA of the thoracoabdominal aorta allows for precise and reproducible assessment of aortic sac size in aneurysm or extent of dissection in thoracoabdominal aortic dissection [33,37-39]. Multiple unenhanced Thoracoabdominal Aortic Aneurysm or Dissection MRA techniques such as time-of-flight, phase-contrast imaging, and SSFP have been developed that allow for evaluation of aortic dissection and aneurysm, including after open surgical repair [44,45]. Even without IV contrast, MRA can be used to precisely evaluate the thoracoabdominal aorta [37,39]. A 2017 observational study comparing AAA measurements in contrast-enhanced CTA and noncontrast-enhanced MRA showed strong agreement, with intraclass coefficient >0.99 and interobserver reproducibility >0.99 for both CTA and MRA [45]. Although some studies have shown more accurate measurements with contrast-enhanced MRA compared with noncontrast-enhanced MRA, other studies have shown equal ability to detect aortic pathology and to measure aortic size [44,50,51]. A 2014 study comparing thoracic aortic measurements and pathology in 76 patients undergoing both contrast- and noncontrast-enhanced MRA showed high agreement between study types, with low intra- and interobserver dependency (intraclass correlation coefficient 0.99) [51]. A similar 2017 study comparing thoracic aorta measurements/findings on contrast- and noncontrast-enhanced MRA performed on a group of 50 patients favored noncontrast-enhanced MRA over contrast-enhanced MRA as the technique of choice because of superior image quality and better vessel sharpness in the ascending aorta [44]. Although these studies do not focus on postsurgical patients, the findings are likely applicable to this patient population.
Thoracoabdominal Aneurysm or Dissection Treatment Planning and Follow Up. Similar to CTA, MRA of the thoracoabdominal aorta allows for precise and reproducible assessment of aortic sac size in aneurysm or extent of dissection in thoracoabdominal aortic dissection [33,37-39]. Multiple unenhanced Thoracoabdominal Aortic Aneurysm or Dissection MRA techniques such as time-of-flight, phase-contrast imaging, and SSFP have been developed that allow for evaluation of aortic dissection and aneurysm, including after open surgical repair [44,45]. Even without IV contrast, MRA can be used to precisely evaluate the thoracoabdominal aorta [37,39]. A 2017 observational study comparing AAA measurements in contrast-enhanced CTA and noncontrast-enhanced MRA showed strong agreement, with intraclass coefficient >0.99 and interobserver reproducibility >0.99 for both CTA and MRA [45]. Although some studies have shown more accurate measurements with contrast-enhanced MRA compared with noncontrast-enhanced MRA, other studies have shown equal ability to detect aortic pathology and to measure aortic size [44,50,51]. A 2014 study comparing thoracic aortic measurements and pathology in 76 patients undergoing both contrast- and noncontrast-enhanced MRA showed high agreement between study types, with low intra- and interobserver dependency (intraclass correlation coefficient 0.99) [51]. A similar 2017 study comparing thoracic aorta measurements/findings on contrast- and noncontrast-enhanced MRA performed on a group of 50 patients favored noncontrast-enhanced MRA over contrast-enhanced MRA as the technique of choice because of superior image quality and better vessel sharpness in the ascending aorta [44]. Although these studies do not focus on postsurgical patients, the findings are likely applicable to this patient population.