Usefulness of PETRA-MRA for Postoperative Follow-Up of Stent-Assisted Coil Embolization of Cerebral Aneurysms

OBJECTIVE: Image evaluation after stent-assisted coil embolization (SAC) for a cerebral aneurysm is difficult with conventional MRA or CTA because of metal artifacts. Pointwise encoding time reduction with radial acquisition (PETRA)-MRA is a noninvasive imaging examination that can reduce metal artifacts. This study aimed to examine whether PETRA-MRA can be used as a follow-up imaging after SAC. METHODS: Twelve patients (eight women and four men; mean age, 66.9 ± 13.2 years) underwent SAC for unruptured aneurysms and were retrospectively evaluated using time-of-flight (TOF)- and PETRA-MRA data from the same follow-up session. Two neurosurgeons independently compared the aneurysm occlusion status and flow visualization score in the stented parent artery (4-point scale, where 4 points represented excellent visualization) between TOF- and PETRA-MRA images. If DSA was performed within 3 months before or after PETRA-MRA, the aneurysm assessment was compared between MRA and DSA. The interobserver agreement for each MRA was evaluated. RESULTS: Nine of the 12 patients underwent DSA within 3 months before and after TOF- and PETRA-MRA. The aneurysm occlusion status on DSA was more consistent with PETRA-MRA (eight of nine cases) than with TOF-MRA (one of nine cases; P = 0.023). The median visualization score of the stented parent artery was significantly higher for PETRA-MRA (4 [interquartile range {IQR} 3–4]) than for TOF-MRA (1 [IQR 1–1], P = 0.003). The interobserver agreement for evaluation of the aneurysm occlusion status and visualization score of the parent artery for PETRA-MRA were excellent (κ = 0.98 and 0.93, respectively). In one case, PETRA-MRA was able to detect aneurysm recurrence, leading to subsequent retreatment. CONCLUSION: PETRA-MRA is a noninvasive examination that can be used to evaluate the occlusion status of aneurysms after SAC and visualize the stented parent artery. PETRA-MRA is useful for repeated follow-up examinations after SAC.