A study evaluating radiation exposure during TEVAR and subsequent follow-up found that cumulative lifetime radiation exposure in these patients is likely to exceed 350 mSv, conferring an increased lifetime risk of at least 2.7% for developing solid-organ malignancy or leukemia [84]. The development of ever-advanced iterative reconstruction algorithms permits the use of lower tube energies, thereby allowing for reduced patient radiation exposure. A recent study highlighted radiation dose reductions ranging from 63% to 69% at standard kilovolt (peak) using a fully iterative reconstruction algorithm as compared with standard filtered back-projection without appreciable changes in conspicuity of endoleaks or in-stent thrombosis [85]. Dual-energy acquisition offers the possibility of eliminating the unenhanced phase via the creation of a virtual noncontrast image set. Another recent study demonstrated near-perfect correlation between single- and dual-phase dual-energy scans in comparison with a traditional three-phase protocol, with 19.5% and 64.1% less radiation exposure, respectively [72]. CT CT Although not ideal given the inability to directly detect endoleaks, unenhanced CT can still offer valuable follow- up information in TEVAR patients with chronic renal insufficiency and stent grafts not amenable to MRA. Unenhanced CT is useful in the assessment of graft migration, aortic rupture, and delineation of vascular calcifications, hematoma, and surgical material that could otherwise be confused for endoleak on CTA examinations [36]. Additionally, by using aneurysm sac diameter as a proxy for graft and anastomotic integrity, unenhanced CT can indirectly suggest endoleak if sac volume increases over time by more than 2% [86]. In patients with stable findings on early postintervention imaging and a low risk of graft complications, follow-up with unenhanced CT complemented by CTA when questions arise may be a viable strategy.
Thoracic Aortic Aneurysm or Dissection Treatment Planning and Follow Up. A study evaluating radiation exposure during TEVAR and subsequent follow-up found that cumulative lifetime radiation exposure in these patients is likely to exceed 350 mSv, conferring an increased lifetime risk of at least 2.7% for developing solid-organ malignancy or leukemia [84]. The development of ever-advanced iterative reconstruction algorithms permits the use of lower tube energies, thereby allowing for reduced patient radiation exposure. A recent study highlighted radiation dose reductions ranging from 63% to 69% at standard kilovolt (peak) using a fully iterative reconstruction algorithm as compared with standard filtered back-projection without appreciable changes in conspicuity of endoleaks or in-stent thrombosis [85]. Dual-energy acquisition offers the possibility of eliminating the unenhanced phase via the creation of a virtual noncontrast image set. Another recent study demonstrated near-perfect correlation between single- and dual-phase dual-energy scans in comparison with a traditional three-phase protocol, with 19.5% and 64.1% less radiation exposure, respectively [72]. CT CT Although not ideal given the inability to directly detect endoleaks, unenhanced CT can still offer valuable follow- up information in TEVAR patients with chronic renal insufficiency and stent grafts not amenable to MRA. Unenhanced CT is useful in the assessment of graft migration, aortic rupture, and delineation of vascular calcifications, hematoma, and surgical material that could otherwise be confused for endoleak on CTA examinations [36]. Additionally, by using aneurysm sac diameter as a proxy for graft and anastomotic integrity, unenhanced CT can indirectly suggest endoleak if sac volume increases over time by more than 2% [86]. In patients with stable findings on early postintervention imaging and a low risk of graft complications, follow-up with unenhanced CT complemented by CTA when questions arise may be a viable strategy.