Magnetic Resonance Angiography after Flow Diversion: The use of complementary MRA techniques to monitor aneurysm occlusion as well as device and arterial branch patency after flow diverter placement

Few studies have been performed to evaluate flow diversion with MRA. They have shown better success for MRA to assess the aneurysm response but limited success for the stent patency. Further, the patency of arterial branches on MRA remains to be explored. 31 consecutive cases of carotid aneurysms treated with flow diversion were retrospectively evaluated with noncontrast time of flight (TOF), contrast enhanced TOF (CTOF) and cine MRA (TWIST) independently by two investigators for aneurysm occlusion, stent patency and arterial branch patency. DSA served as the gold standard technique. There were 6 males and 25 females in the age range of years (mean ±SD). Stent patency, aneurysm occlusion and branch patency, mostly revealed substantial to perfect interobserver agreement (k >0.60). The sensitivity, specificity, positive and negative predictive values for the stent patency on source images of TOF were 0.99,0.84, 0.42 and 0.99 and on CTOF were 0.99, 0.89, 0.50 and 0.99 respectively.Sensitivity for the aneurysm response on the three MRAs ranged from 0.88 to 0.93,specificity from 0.64 to 0.75, positive predictive value from 0.69 to 0.79 and negative predictive value from 0.86 to 0.90. Sensitivity for the arterial branch patency among the three MRAs, ranged from 0.55 to 0.93, specificity from 0.61 to 0.68, positive predictive value from 0.79 to 0.93 and negative predictive value from 0.22 to 0.90. Aneurysm occlusion, stent patency and arterial branch patency in flow diversion can be successfully evaluated with the combination of three MRA techniques.