Diagnostic Performance of Pointwise Encoding Time Reduction with Radial Acquisition Subtraction-based MR Angiography in the Follow-up of Intracranial Aneurysms after Clipping.

PURPOSE: While follow-up assessment of clipped aneurysms (CAs) using magnetic resonance angiography (MRA) can be challenging due to susceptibility artifacts, a novel MRA sequence pointwise encoding time reduction with radial acquisition (PETRA) subtraction-based MRA, has been developed to reduce these artifacts. The aim of the study was to validate the diagnostic performance of PETRA-MRA by comparing it with digital subtraction angiography (DSA) as a reference for follow-up of CAs using a 3T MR scanner. METHODS: Patients with clipping who underwent both PETRA-MRA and DSA between September 2019 and December 2021 were retrospectively included. Two neuroradiologists independently reviewed with the reconstructed images of PETRA-MRA to assess the visibility of the arteries around the clips and aneurysm recurrence or remnants of CA using a 3-point scale. The diagnostic accuracy of PETRA-MRA was evaluated in comparison to DSA. RESULTS: The study included 34 patients (28 females, mean age 59 ± 9.6 years) with 48 CAs. The PETRA-MRA allowed visualization of the parent vessels around the clips in 98% of cases, compared to 39% with time-of-flight (TOF) MRA (p < 0.0001). The DSA confirmed 14 (29.2%) residual or recurrent aneurysms. The PETRA-MRA demonstrated a high accuracy, specificity, positive predictive value, and negative predictive value of 99.2%, 100%, 100%, and 97.8%, respectively, while the sensitivity was 66.7%. CONCLUSION: This retrospective study demonstrates that PETRA-MRA provides excellent visibility of adjacent vessels near clips and has a high diagnostic accuracy in detecting aneurysm remnants or recurrences in CAs. Further prospective studies are warranted to establish its utility as a reliable alternative for follow-up after clipping.

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.

Pointwise encoding time reduction with radial acquisition in subtraction-based magnetic resonance angiography to assess saccular unruptured intracranial aneurysms at 3 Tesla.

PURPOSE: To investigate the clinical utility of pointwise encoding time reduction with radial acquisition in subtraction-based magnetic resonance angiography (PETRA-MRA) and time-of-flight magnetic resonance angiography (TOF-MRA) to evaluate saccular unruptured intracranial aneurysms (UIAs). METHODS: A total of 49 patients with 54 TOF-MRA-identified saccular UIAs were enrolled. The morphologic parameters, contrast-to-noise-ratios (CNRs), and sharpness of aneurysms were measured using PETRA-MRA and TOF-MRA. Two radiologists independently evaluated subjective image scores, focusing on aneurysm signal homogeneities and sharpness depictions using a 4-point scale: 4, excellent; 3, good; 2, poor; 1, not assessable. PETRA-MRA and TOF-MRA acoustic noises were measured. RESULTS: All aneurysms were detected with PETRA-MRA. The morphologic parameters of 15 patients evaluated with PETRA-MRA were more closely correlated with those receiving computed tomography angiography over those receiving TOF-MRA. No significant differences between PETRA-MRA and TOF-MRA parameters were seen in the 54 UIAs (p > 0.10), excluding those with inflow angles (p < 0.05). In four patients with inflow angles on PETRA-MRA, the angles were more closely related to those of digital subtraction angiography than those of TOF-MRA. CNRs between TOF-MRA and PETRA-MRA were comparable (p = 0.068), and PETRA-MRA sharpness values and subjective image scores were significantly higher than those of TOF-MRA (p < 0.001). Inter-observer agreements were excellent for both PETRA-MRA and TOF-MRA (intraclass correlation coefficients were 0.90 and 0.97, respectively). The acoustic noise levels of PETRA-MRA were much lower than those of TOF-MRA (59 vs.73 dB, p < 0.01). CONCLUSIONS: PETRA-MRA, with better visualization of aneurysms and lower acoustic noise levels than TOF-MRA, showed a superior diagnostic performance for depicting saccular UIAs.