The effectiveness of 3T time-of-flight magnetic resonance angiography for follow-up evaluations after the stent-assisted coil embolization of cerebral aneurysms

Safety and efficacy of the novel Alpha stent for the treatment of intracranial wide-necked aneurysm

The Alpha stent is an intracranial closed-cell stent with a unique mesh design to enhance wall apposition. It recently underwent structural modifications to facilitate easier stent deployment. This study aimed to evaluate the safety and efficacy of stent-assisted coil embolization for unruptured intracranial aneurysms using the Alpha stent. Between January 2021 and November 2021, 35 adult patients with 35 unruptured intracranial aneurysms in the distal internal carotid artery were prospectively enrolled. For efficacy outcomes, magnetic resonance angiography at the 6-month follow-up was evaluated using the Raymond-Roy occlusion classification (RROC). The safety outcome evaluated the occurrence of symptomatic procedure-related neurological complications up to 6 months postoperatively. Technical success was achieved in 34/35 (97.1%). Six months postoperatively, aneurysm occlusion showed RROC I in 32/35 (91.4%) and RROC II in 3/35 (8.6%) patients. Procedure-related neurologic complications occurred in one patient (2.9%) who experienced hemiparesis due to acute lacunar infarction, which resulted in a 6-month mRS score of 1. The Alpha stent demonstrated excellent efficacy and safety outcomes in stent-assisted coil embolization of unruptured distal ICA aneurysms. The recent structural modifications allowed for easier stent delivery and deployment.Clinical trial registration number: KCT0005841; registration date: 28/01/2021.

Intracranial aneurysms treated with stent-assisted coil embolization: evaluation with four-dimensional ultrashort-TE MR angiography

OBJECTIVES

As a novel follow-up method for intracranial aneurysms treated with stent-assisted coil embolization (SACE), we developed four-dimensional magnetic resonance angiography (MRA) with minimized acoustic noise utilizing ultrashort-echo time (4D mUTE-MRA). We aimed to assess whether 4D mUTE-MRA is useful for the evaluation of intracranial aneurysms treated with SACE.

METHODS

This study included 31 consecutive patients with intracranial aneurysm treated with SACE who underwent 4D mUTE-MRA at 3 T and digital subtraction angiography (DSA). For 4D mUTE-MRA, five dynamic MRA images with a spatial resolution of 0.5 × 0.5 × 0.5 mm3 were obtained every 200 ms. Two readers independently reviewed the 4D mUTE-MRA images to evaluate the aneurysm occlusion status (total occlusion, residual neck, and residual aneurysm) and the flow in the stent using a 4-point scale (from 1 [not visible] to 4 [excellent]). The interobserver and intermodality agreement was assessed using κ statistics.

RESULTS

On DSA images, 10 aneurysms were classified as total occlusion, 14 as residual neck, and 7 as residual aneurysm. In terms of aneurysm occlusion status, the intermodality and interobserver agreement was excellent (κ = 0.92 and κ = 0.96, respectively). For the flow in the stents on 4D mUTE-MRA, the mean score was significantly higher for single stents than multiple stents (p < .001) and for open-cell type stents than closed-cell type (p < .01).

CONCLUSIONS

4D mUTE-MRA is a useful tool with a high spatial and temporal resolution for the evaluation of intracranial aneurysms treated with SACE.

KEY POINTS

• In the evaluation of intracranial aneurysms treated with SACE on 4D mUTE-MRA and DSA, the intermodality and interobserver agreement in aneurysm occlusion status was excellent. • 4D mUTE-MRA shows good to excellent visualization of flow in the stents, especially for cases treated with a single or open-cell stent. • 4D mUTE-MRA can provide hemodynamic information related to embolized aneurysms and the distal arteries to stented parent arteries.

Usefulness of Pointwise Encoding Time Reduction with Radial Acquisition-Magnetic Resonance Angiography after Endovascular Treatment for Intracranial Aneurysms

PURPOSE

Imaging follow-up after endovascular treatment is important; however, time-of-flight magnetic resonance angiography (TOF-MRA) has limitations associated with magnetic susceptibility and radiofrequency shielding caused by the stent and coils. We evaluated the diagnostic performance of pointwise encoding time reduction with radial acquisition (PETRA)-MRA after endovascular treatment for intracranial aneurysms.

MATERIAL AND METHODS

A total of 186 patients with 211 aneurysms who underwent both pointwise encoding time reduction with radial acquisition- and time-of-flight magnetic resonance angiography in the same imaging session for follow-up after endovascular treatment. We subjectively graded the overall image quality, visualization of treated sites, and occlusion status.

RESULTS

Although the overall image quality scores of pointwise encoding time reduction with radial acquisition-magnetic resonance angiography were significantly lower than those of time-of-flight magnetic resonance angiography for both observers (4.04 ± 0.81 vs. 4.85 ± 0.35 [observer 1], 4.60 ± 0.69 vs. 4.94 ± 0.24 [observer 2]) (both P < .001), the visibility of treated sites using pointwise encoding time reduction with radial acquisition-magnetic resonance angiography was significantly better than that of time-of-flight magnetic resonance angiography overall (4.27 ± 0.97 vs. 3.42 ± 1.01; P < .001), in the distal internal carotid artery (4.46 ± 0.79 vs. 3.40 ± 1.00; P < .001), and in the middle cerebral artery (4.19 ± 0.93 vs. 3.08 ± 0.53, P = 0.007). Pointwise encoding time reduction with radial acquisition-magnetic resonance angiography showed a higher area under the curve than time-of-flight magnetic resonance angiography for the evaluation of treated aneurysm occlusion, except for posterior circulation aneurysms.

CONCLUSIONS

Pointwise encoding time reduction with radial acquisition-magnetic resonance angiography showed better visualization of treated sites and better diagnostic performance than time-of-flight magnetic resonance angiography for anterior circulation aneurysms. However, Pointwise encoding time reduction with radial acquisition-magnetic resonance angiography showed limitations in the follow-up evaluation of posterior circulation aneurysms.

Follow-Up Assessment of Intracranial Aneurysms Treated with Endovascular Coiling: Comparison of Compressed Sensing and Parallel Imaging Time-of-Flight Magnetic Resonance Angiography

The aim of our study was to compare compressed sensing (CS) time-of-flight (TOF) magnetic resonance angiography (MRA) with parallel imaging (PI) TOF MRA in the evaluation of patients with intracranial aneurysms treated with coil embolization or stent-assisted coiling. We enrolled 22 patients who underwent follow-up imaging after intracranial aneurysm coil embolization. All patients underwent both PI TOF and CS TOF MRA during the same examination. Image evaluation aimed to compare the performance of CS to PI TOF MRA in determining the degree of aneurysm occlusion, as well as the depiction of parent vessel and vessels adjacent to the aneurysm dome. The reference standard for the evaluation of aneurysm occlusion was PI TOF MRA. The inter-modality agreement between CS and PI TOF MRA in the evaluation of aneurysm occlusion was almost perfect (κ  =  0.98, p  <  0.001) and the overall inter-rater agreement was substantial (κ  =  0.70, p  <  0.001). The visualization of aneurysm parent vessel in CS TOF images compared with PI TOF images was evaluated to be better in 11.4%, equal in 86.4%, and worse in 2.3%. CS TOF MRA, with almost 70% scan time reduction with respect to PI TOF MRA, yields comparable results for assessing the occlusion status of coiled intracranial aneurysms. Short scan times increase patient comfort, reduce the risk of motion artifacts, and increase patient throughput, with a resulting reduction in costs. CS TOF MRA may therefore be a potential replacement for PI TOF MRA as a first-line follow-up examination in patients with intracranial aneurysms treated with coil embolization.

The Use of Pointwise Encoding Time Reduction With Radial Acquisition MRA to Assess Middle Cerebral Artery Stenosis Pre- and Post-stent Angioplasty: Comparison With 3D Time-of-Flight MRA and DSA

Background and Purpose: 3D pointwise encoding time reduction magnetic resonance angiography (PETRA-MRA) is a promising non-contrast magnetic resonance angiography (MRA) technique for intracranial stenosis assessment but it has not been adequately validated against digital subtraction angiography (DSA) relative to 3D-time-of-flight (3D-TOF) MRA. The aim of this study was to compare PETRA-MRA and 3D-TOF-MRA using DSA as the reference standard for intracranial stenosis assessment before and after angioplasty and stenting in patients with middle cerebral artery (MCA) stenosis. Materials and Methods: Sixty-two patients with MCA stenosis (age 53 ± 12 years, 43 males) underwent MRA and DSA within a week for pre-intervention evaluation and 32 of them had intracranial angioplasty and stenting performed. The MRAs' image quality, flow visualization within the stents, and susceptibility artifact were graded on a 1-4 scale (1 = poor, 4 = excellent) independently by three radiologists. The degree of stenosis was measured by two radiologists independently on DSA and MRAs. Results: There was an excellent inter-observer agreement for stenosis assessment on PETRA-MRA, 3D-TOF-MRA, and DSA (ICCs > 0.90). For pre-intervention evaluation, PETRA-MRA had better image quality than 3D-TOF-MRA (3.87 ± 0.34 vs. 3.38 ± 0.65, P < 0.001), and PETRA-MRA had better agreement with DSA for stenosis measurements compared to 3D-TOF-MRA (r = 0.96 vs. r = 0.85). For post-intervention evaluation, PETRA-MRA had better image quality than 3D-TOF-MRA for in-stent flow visualization and susceptibility artifacts (3.34 ± 0.60 vs. 1.50 ± 0.76, P < 0.001; 3.31 ± 0.64 vs. 1.41 ± 0.61, P < 0.001, respectively), and better agreement with DSA for stenosis measurements than 3D-TOF-MRA (r = 0.90 vs. r = 0.26). 3D-TOF-MRA significantly overestimated the stenosis post-stenting compared to DSA (84.9 ± 19.7 vs. 39.3 ± 13.6%, p < 0.001) while PETRA-MRA didn't (40.6 ± 13.7 vs. 39.3 ± 13.6%, p = 0.18). Conclusions: PETRA-MRA is accurate and reproducible for quantifying MCA stenosis both pre- and post-stenting compared with DSA and performs better than 3D-TOF-MRA.

The feasibility of non-contrast-enhanced zero echo time magnetic resonance angiography for characterization of intracranial atherosclerotic disease

Background

Accurate and non-invasive assessment of intracranial atherosclerotic disease (ICAD) is important because of its effect on treatment planning. The aim of this study is to investigate if zero echo time (zTE) magnetic resonance angiography (zTE-MRA) is feasible in the characterization of ICAD.

Methods

A total of 175 patients with ICAD were recruited. ZTE-MRA and time-of-flight (TOF)-MRA sequences were conducted for all participants using a 3T clinical MR system. Forty-one patients also underwent digital subtraction angiography (DSA), and were confirmed to have intracranial arterial stenosis (ICAS). Weighted kappa (κ) statistics were used to assess the inter-observer agreement and diagnostic consistency of both zTE- and TOF-MRA, using DSA as a reference. The Wilcoxon signed-rank test was used to evaluate differences in image quality between zTE- and TOF-MRA images. The nonparametric test of multiple paired samples was used to compare the results of vascular stenosis diagnosis between zTE-, TOF-MRA and DSA.

Results

Supported by high inter-observer agreement (weighted κ=0.78), zTE-MRA generated significantly higher scores than TOF-MRA for susceptibility artifact signal (mean: 3.03±0.98 vs. 2.72±1.09; P=0.017) and flow signal in parent artery (mean: 3.63±0.49 vs. 3.07±0.82; P<0.001). Additionally, zTE-MRA showed more robust diagnostic performance than TOF-MRA for patients with ICAD and degree of vascular stenosis (P<0.05), and was highly consistent with reference DSA images (weighted κ=0.80).

Conclusions

ZTE-MRA has potential for use as a routine clinical method for patients with ICAD.

Application of 3D T1-SPACE combined with 3D-TOF sequence for follow-up evaluation of stent-assisted coil embolization for intracranial aneurysm

OBJECTIVES

To assess 3D T1-SPACE combined with 3D-TOF sequence for follow-up evaluation of stent-assisted coil embolization for intracranial aneurysm.

MATERIALS AND METHODS

Between Oct 2018 and May 2019, we enrolled 25 patients with intracranial aneurysm who underwent stent-assisted coil embolization. All patients were followed up for 6 to10 months after endovascular treatment (EVT) using 3D-TOF MRA, 3D T1-SPACE and DSA to evaluate aneurysm occlusion and parent artery patency.

RESULTS

With regards to aneurysm occlusion, the specificity of 3D-TOF MRA was 86.9% (20/23) and the accuracy was 84% (21/25). There was no statistical significance (P ​= ​0.409) compared with the DSA. The parent artery by 3D-TOF MRA showed that there were 14 patients with grade 3, 8 patients with grade 2 and 3 patients with grade 1. However, 3D T1-SPACE showed that all 25 patients were grade 4, and were clearly displayed without metal artifacts. The comparison of the two MR techniques demonstrated that 3D T1-SPACE was superior to 3D-TOF MRA in the evaluation of parent artery (P<0.001).

CONCLUSIONS

3D T1-SPACE sequence provides better image quality and higher accuracy for evaluating stented parent arteries compared to TOF-MRA. This study also shows that 3D-TOF MRA has a merit to evaluate aneurysm occlusion. The combination of these two modalities can be used as an optional follow-up evaluation after EVT of intracranial aneurysms.

Knowledge framework and emerging trends in intracranial aneurysm magnetic resonance angiography: a scientometric analysis from 2004 to 2020

Background

As magnetic resonance angiography (MRA) has been increasingly used in the follow-up of intracranial aneurysms (IAs) as a non-invasive technique, the knowledge framework and areas of research interest in intracranial aneurysms magnetic resonance angiography (IAMRA) change approximately every 10 years. However, few studies have quantitatively analyzed the published literature in this field. In the present study, we used scientometrics to survey the knowledge field, development trends, and research focus of IAMRA with the aim of providing a reference for further study.

Methods

We collected articles on IAMRA published from 2004 (Jan 1, 2004) to 2020 (May 24, 2020). Web of Science Core Collection databases (WoSCCd) including the Science Citation Index Expanded were searched. An experienced staff member from the Department of Radiology at Southern Medical University, assisted in screening articles for relevant articles. We used ArcGIS (a mapping and location analytics platform) to perform geographic visualization. Excel 2016 was used to analyze the literature data, including number of publications, impact factor (IF), and publication year. CiteSpace V was used to conduct a series of literature feature clustering, including author co-citation analysis, reference co-citation analysis (RCA), and burst keywords analysis.

Results

A total of 1,272 articles on IAMRA published between 2004 and 2020 were included. Of 257 journals, American Journal of Neuroradiology (IF 2018: 3.256) published the most IAMRA articles (109 publications, 8.57%), followed by Journal of Neurosurgery (IF 2018: 4.131, 51 publications, 4.16%), and Neuroradiology (IF 2018: 2.504, 51 publications, 4.01%). Of 56 countries, the USA published the most, with 347 articles [27.28%, IF: 3.14 (average IF of all journals in the country)], followed by Japan (242 articles, 19.03%, IF: 2.38), Germany (135 articles, 10.61%, IF: 3.21), and China (101 articles, 7.94%, IF: 2.86). A total of 1387 institutions published articles, with the Mayo Clinic publishing the most (33 articles, 2.59%), followed by Shanghai Jiao Tong University (25 article, 1.97%), Seoul National University (23 articles, 1.81%), and University Medical Center Utrecht (19 articles, 1.49%). Of 399 authors, Rinkel ranked first with 19 articles, followed by Li MH (18 articles), Uchino A (15 articles), and Saito N (13 articles). Cluster RCA showed that the first cluster was "#0 growth", followed by "#1 Guglielmi detachable coils". Timeline views showed that the time span of "#0 growth" was the closest to today. The modularity value was 0.6971, and the mean silhouette value was 0.5477. According to the burst keyword analysis, "risk factors associated to rupture" was the topic with the strongest burst since 2017. Studies conducted in several countries suggested that age is inversely related to the risk of rupture, which implies the importance of MRA follow-up for patients of different age.

Conclusions

From 2004 to 2020, the number of published IAMRA-related articles gradually increased. The USA and Western Europe lead in the field, with a concentration of cutting-edge talents and high-level scientific research institutions. A synthesis of the clustering results of RCA and burst keyword analysis indicated that unruptured IA growth, stent-assisted coil embolization, and risk factors associated to rupture were the current hotspots in IAMRA research.

The sensitivity and specificity of TOF-MRA compared with DSA in the follow-up of treated intracranial aneurysms

BACKGROUND

Time-of-flight magnetic resonance angiography (TOF-MRA) is widely used in detecting intracranial aneurysms (IA), but it is limited and controversial for use during follow-up to assess the outcome of interventional coiling or clipping surgery.

METHODS

To evaluate the specificity and sensitivity of using TOF-MRA as an imaging follow-up for IA with different treatments. A total of 280 patients with 326 treated IA underwent simultaneous TOF-MRA and digital subtraction angiography (DSA) as follow-up imaging on the same day. All images were independently reviewed by two neurosurgeons and two radiologists. The consensus evaluation of intra-arterial DSA as a reference test was used to evaluate the result of aneurysm occlusions. The aneurysmal embolization status was assessed with two ratings involving complete or incomplete occlusions. We calculated the sensitivity, specificity, negative predictive value, and positive predictive value of three-dimensional-TOF-MRA to investigate the diagnostic performance.

RESULTS

Overall sensitivity and specificity of TOF-MRA for diagnosing the remnant were 83.3% and 95.2%, respectively. The sensitivity and specificity of interventional therapy was 90.0% and 94.2%, respectively, while the clipping group showed sensitivity and specificity of 50.0% and 100%, respectively. For additional groups, involving coil only, stent-assisted, and flow diverter, the analysis of interventional therapy showed sensitivities and specificities of 100.0% and 90.1%, 66.7% and 95.1%, and 91.7% and 100%, respectively.

CONCLUSIONS

TOF-MRA can be used as a first-line noninvasive imaging modality during follow-up, especially for the patients treated with a pipeline embolization device and coils only. But it may not be enough for clipped aneurysms.

Validity of PETRA-MRA for Stent-Assisted Coil Embolization of Intracranial Aneurysms

Objective

Pointwise encoding time reduction with radial acquisition (PETRA) using magnetic resonance angiography (MRA) is a non-enhanced MRA technique employing an ultrashort echo time, and is known to significantly reduce the magnetic susceptibility of coils and stents during post-embolization imaging. We evaluated the quality of PETRA-MRA images for use at the follow-up assessment of stent-assisted coil embolization procedures performed to treat aneurysms.

Methods

A total of six aneurysm patients who were treated by stent-assisted coil embolization were included. All patients underwent PETRA-MRA, time-of-flight (TOF)-MRA performed with MAGNETOM Skyra (Siemens), and digital subtraction angiography (DSA) performed with Infinix Celeve-i INFX-8000V (Canon Medical Systems) and Allura Clarity FD20/15 (Philips). The PETRA-MRA images were compared with those from DSA and TOF-MRA to validate the aneurysm occlusion status and visually assess the blood flow within the stent. Four independent specialists graded occlusion status and flow visualization through the stent using a four-point scale, where 4 points represented excellent visualization of flow within the stent.

Results

The aneurysm was located in the internal carotid artery in two patients, the middle cerebral artery in two patients, the top of the basilar artery in one patient, and the vertebral artery-posterior inferior cerebellar artery (VA-PICA) in one patient. Three patients were treated using a Neuroform Atlas Stent system, one using an Enterprise2 VRD, one using two Neuroform Atlas stents for Y-stenting, and the remaining patient using a Neuroform Atlas and an Enterprise2 VRD for Y-stenting. With DSA, the postoperative aneurysm occlusion status was neck remnant (NR) in five cases and complete obliteration (CO) in one case. DSA and PETRA-MRA evaluations demonstrated an equal occlusion status in five of six cases, whereas DSA and TOF-MRA were equal in two of six cases. The mean visualization score for PETRA-MRA was 3.33 ± 0.82, whereas that for TOF-MRA was 2.17 ± 1.33. On the PETRA-MRA images, blood flow through the stent was well-visualized and produced an aneurysm occlusion status score comparable to DSA, especially in the three cases using the Neuroform Atlas Stent System where the visualization was scored 4 points. In the case of the VA-PICA aneurysm, for which an Enterprise2 VRD was used, PETRA-MRA images were insufficient for postoperative assessment.

Conclusion

PETRA-MRA can provide good visualization of the blood flow within a stent and displays a clear blood signal near the coils, barring small magnetic susceptibility artifacts. Therefore, PETRA-MRA may be an effective option for follow-up imaging after stent-assisted coil embolization.

Usefulness of 3D T1-SPACE in Combination With 3D-TOF MRA for Follow-Up Evaluation of Intracranial Aneurysms Treated With Pipeline Embolization Devices

Object: Follow-up evaluation of intracranial aneurysms treated by flow-diverting stents using MRI is challenging due to the presence of imaging artifacts. This study evaluated 3D T1-SPACE in combination with 3D-TOF sequence for follow-up evaluation of intracranial aneurysms treated with Pipeline embolization devices.

Methods: Forty patients with 53 intracranial aneurysms who were treated with Pipeline Embolization Devices from October 2018 to July 2019 were enrolled in this study. All patients were evaluated for aneurysm occlusion and stent patency 4 to 7 months post-treatment using 3D T1-SPACE sequence, 3D-TOF MRA, and DSA examinations.

Results: With regards to aneurysm occlusion, the intermodality (DSA and 3D-TOF MRA) agreement was good (κ = 0.755). The specificity of 3D-TOF MRA was 94.4% (34/36), the sensitivity was 76.5% (13/17), the total coincidence rate was 88.7% (47/53). With regards to the patency of the stented arteries after PED treatment, 3D T1-SPACE sequence was more accurate compared to 3D-TOF MRA (Z = −6.283, P < 0.001), with a no-artifact rate of 95.7% (44/46).

Conclusions: 3D T1-SPACE sequence provides better image quality and higher accuracy for evaluating stented parent arteries compared to TOF-MRA. 3D-TOF MRA may be valuable in the evaluation of aneurysm occlusion. The combination of these two modalities may be used for long-term follow-up of intracranial aneurysms treated with Pipeline Embolization Devices.

Management of incidentally found unruptured intracranial aneurysms

Incidentally found unruptured intracranial aneurysms are increasing because of the popularity of medical checkups with cerebrovascular imaging and the recent growing interest in health. Accordingly, surgical or endovascular treatments are also increasing in prevalence to improve aneurysm-related symptoms or prevent the rupture of aneurysms causing devastating conditions. However, treatment plans should be carefully determined based on the natural history of aneurysms, comorbidities of the patients, and institutional situations because of the relatively low risk of rupture, no uncommon treatment-related complications, and considerable economical and psychological burdens. Recently, domestic and international clinical guidelines for unruptured intracranial aneurysms were introduced, and the guidelines have been continuously revised according to advancements in imaging and treatment techniques. Here, this review paper introduces the clinical characteristics of unruptured intracranial aneurysms including the epidemiology, risk factors of development, growth and rupture, natural course, symptoms and signs, imaging tools for diagnosis and follow-up, and treatment methods. This paper also includes recent international prospective trials, analytic reports with big data from national health insurance and health insurance review and assessment services, and the guidelines of Korea and other foreign countries.

Motion Correction of Dual Volume Reconstruction of Three‑dimensional Digital Subtraction Angiography for Follow‑up Evaluation of Intracranial Coiled Aneurysms

Purpose

To evaluate the usefulness of the "Motion Correction" function of the dual volume-3D-volume-rendering technique (DV-3D-VRT) in follow-up digital subtraction angiography (DSA) of intracranial coiled aneurysms.

Materials and Methods

This study used data collected from consecutive, follow-up DSAs after the coiling of 64 intracranial aneurysms in 59 patients. We performed subtracted 3D-rotational angiographies (3D-RAs) on all DSAs and obtained DV-3D-VRT images. We then assessed recurrence using DV-3D-VRT images with and without the motion correction functions (MC(+) vs. MC(-)) and observed which method showed better agreement with the reference assessment (using a combination of 2D DSA and TOF MRA images).

Results

The recurrence of MC(-) DV-3D-VRT images showed 51.6% (33/64) agreement with the reference assessment, whereas the MC(+) DV-3D-VRT images showed 78.1% (50/64) (P = 0.035, McNemar test).

Conclusion

Motion correction is a useful complementary imaging technique in evaluating aneurysm recurrence after endovascular embolization. MC(+) DV-3D-VRT image showed higher inter-observer agreement than MC(-) DV-3D-VRT.

Usefulness of Noncontrast-Enhanced Silent Magnetic Resonance Angiography (MRA) for Treated Intracranial Aneurysm Follow-up in Comparison with Time-of-Flight MRA

BACKGROUND

Flow visualization in time-of-flight magnetic resonance angiography (TOF MRA) is limited for treated intracranial aneurysms owing to magnetic susceptibility and radiofrequency shielding.

OBJECTIVE

To assess the clinical usefulness of noncontrast-enhanced magnetic resonance angiography (MRA) using a silent scan (silent MRA) as a follow-up imaging modality in patients with treated intracranial aneurysms.

METHODS

A total of 119 patients with 126 treated aneurysms underwent silent MRA and TOF MRA during the same scan session. Two neuroradiologists independently assessed overall image quality and visualization of the treated site using a 5-point Likert scale to compare the 2 image sets. We used receiver operating characteristic (ROC) curve analysis to investigate the diagnostic performance of the 2 MRA methods in evaluating aneurysm occlusion. Interobserver reliability was also assessed using weighted kappa statistics.

RESULTS

The overall image quality scores of silent MRA and TOF MRA were 4.04 ± 0.22 and 4.64 ± 0.48, respectively (P &lt; .001), and interobserver agreement was substantial (P &lt; .001). For the treated site, the score of flow visualization on silent MRA was higher than that on TOF MRA, 3.94 ± 0.94 vs 2.59 ± 1.37 (P &lt; .001), with substantial interobserver agreement (P &lt; .001). ROC curve analysis showed that silent MRA was superior to TOF MRA in diagnostic performance (area under the curve [AUC] = 0.962; 95% CI: 0.931-0.982 vs AUC = 0.843; 95% CI: 0.792-0.886; P &lt; .001).

CONCLUSION

Silent MRA can be useful to evaluate treated intracranial aneurysms during follow-up without radiation exposure and use of contrast material. It is characterized by higher diagnostic performance and superior visualization for the treated site.

MRA versus DSA for the follow-up imaging of intracranial aneurysms treated using endovascular techniques: a meta-analysis

BACKGROUND

Treated aneurysms must be followed over time to ensure durable occlusion, as more than 20% of endovascularly treated aneurysms recur. While digital subtraction angiography (DSA) remains the gold standard, magnetic resonance angiography (MRA) is attractive as a non-invasive follow-up technique. Two different MRA techniques have traditionally been used: time-of-flight (TOF) and contrast-enhanced (CE) MRA. We analysed data from studies comparing MRA techniques with DSA for the follow-up of aneurysms undergoing endovascular treatment. Subgroup analysis of stent-assisted coiling (SAC) and flow diversion (FD) techniques was completed.

METHODS

Comprehensive searches using the Embase, PubMed, and Cochrane databases were performed and updated to November 2018. Pooled sensitivity and specificity were calculated using aneurysm occlusion status as defined by the Raymond-Roy occlusion grading scale.

RESULTS

The literature search yielded 1579 unique titles. Forty-three studies were included. For TOF-MRA, sensitivity and specificity of all aneurysms undergoing endovascular therapy were 88% and 94%, respectively. For CE-MRA, the sensitivity and specificity were 88% and 96%, respectively. For SAC and FD techniques, sensitivity and specificity of TOF-MRA were 86% and 95%, respectively. CE-MRA had sensitivity and specificity of 90% and 92%.

CONCLUSION

MRA is a reliable modality for the follow-up of aneurysms treated using endovascular techniques. While the data are limited, MRA techniques can also be used to reliably follow patients undergoing FD and SAC. However, clinical factors must be used to optimize follow-up regimens for individual patients.

Usefulness of Silent MR Angiography for Intracranial Aneurysms Treated with a Flow-Diverter Device

BACKGROUND AND PURPOSE

The flow-diverter device has been established as a treatment procedure for large unruptured intracranial aneurysms. The purpose of this study was to compare the usefulness of Silent MR angiography and time-of-flight MRA to assess the parent artery and the embolization state of the aneurysm after a flow-diverter placement.

MATERIALS AND METHODS

Seventy-eight large, unruptured internal carotid aneurysms in 78 patients were the subjects of this study. After 6 months of treatment, they underwent follow-up digital subtraction angiography, Silent MRA, and TOF-MRA, performed simultaneously. All images were independently reviewed by 2 neurosurgeons and 1 radiologist and rated on a 4-point scale from 1 (not visible) to 4 (excellent) to evaluate the parent artery. The aneurysmal embolization status was assessed with 2 ratings: complete or incomplete occlusion.

RESULTS

The mean scores of Silent MRA and TOF-MRA regarding the parent artery were 3.18 ± 0.72 and 2.31 ± 0.86, respectively, showing a significantly better score with Silent MRA (P < .01). In the assessment of the embolization of aneurysms on Silent MRA and TOF-MRA compared with DSA, the percentages of agreement were 91.0% and 80.8%, respectively.

CONCLUSIONS

Silent MRA is superior for visualizing blood flow images inside flow-diverter devices compared with TOF-MRA. Furthermore, Silent MRA enables the assessment of aneurysmal embolization status. Silent MRA is useful for assessing the status of large and giant unruptured internal carotid aneurysms after flow-diverter placement.

Pointwise Encoding Time Reduction with Radial Acquisition with Subtraction-Based MRA during the Follow-Up of Stent-Assisted Coil Embolization of Anterior Circulation Aneurysms

BACKGROUND AND PURPOSE

Time-of-flight MR angiography, though widely used after coil embolization, is associated with limitations owing to magnetic susceptibility and radiofrequency shielding following stent-assisted coil embolization. We evaluated the pointwise encoding time reduction with radial acquisition (PETRA) sequence in subtraction-based MRA (qMRA) using an ultrashort TE relative to TOF-MRA during the follow-up of stent-assisted coil embolization for anterior circulation aneurysms.

MATERIALS AND METHODS

Twenty-five patients (3 men and 22 women; mean age, 59.1 ± 14.0 years) underwent stent-assisted coil embolization for anterior circulation aneurysms and were retrospectively evaluated using TOF-MRA and PETRA qMRA data from the same follow-up session. Two neuroradiologists independently reviewed both MRA findings and subjectively graded flow within the stents (relative to the latest DSA findings) and occlusion status (complete occlusion or neck/aneurysm remnant). Interobserver and intermodality agreement for TOF-MRA and PETRA qMRA were evaluated.

RESULTS

The mean score for flow visualization within the stents was significantly higher in PETRA qMRA than in TOF-MRA (P < .001 for both observers), and good interobserver agreement was reported (κ = 0.63). The aneurysm occlusion status of PETRA qMRA (observer 1, 92.0%; observer 2, 88.0%) was more consistent with DSA than with TOF-MRA (observer 1, 76.0%; observer 2, 80.0%), and there was a better intermodality agreement between DSA and PETRA qMRA than between DSA and TOF-MRA.

CONCLUSIONS

These findings indicate that PETRA qMRA is a useful follow-up technique for patients who have undergone stent-assisted coil embolization for anterior circulation aneurysms.

[Imaging Parameter Optimization of Non-contrast Three-dimensional Time-of-flight Magnetic Resonance Angiography for Patients with Intracranial Stents Using a 1.5 T Magnetic Resonance Imaging System]

The imaging parameters of non-contrast three-dimensional time-of-flight magnetic resonance angiography (3D TOF-MRA) were optimized to improve the image quality for patients treated using stent-assisted coiling. A simulated blood flow phantom with three types of stents (Enterprise 2, Neuroform Atlas, and LVIS) was imaged by changing echo time (TE), band width (BW), flip angle (FA), and matrix (phase, frequency). The difference between the signal intensity in the simulated vessel and the background was measured at each imaging condition. The ratio of this difference with and without the stent was evaluated as the relative in-stent signal (RIS). In addition, the error ratio of the stent lumen diameter was assessed by comparing the full width at half maximum (FWHM) to that measured by 3D X-ray angiography. The RIS was higher in order of LVIS, Neuroform Atlas, and Enterprise 2 in all conditions. The RIS was higher in imaging conditions with short TE, narrow BW, high FA, and large phase matrix. The highest RIS was seen with a frequency matrix of 320 in the Enterprise 2 and 256 in the others. FWHM error ratio was smaller in the same order as the RIS. FWHM error ratio was smaller in imaging conditions with short TE, large frequency matrix (>384), large phase matrix (>224), and high FA (>20°). Imaging conditions of 3D TOF-MRA that were effective to improve the image quality for stent lumen evaluation were short TE and high spatial resolution.

Usefulness of contrast-enhanced and TOF MR angiography for follow-up after low-profile stent-assisted coil embolization of intracranial aneurysms

BACKGROUND

Low-profile, self-expandable stents are used to treat wide-neck aneurysms located on the smaller distal intracranial arteries. This study aimed to assess the usefulness of time-of-flight (TOF) and contrast-enhanced (CE) magnetic resonance angiography (MRA) for follow-up after LEO Baby stent (LBS)-assisted coil embolization.

METHODS

Twenty-four aneurysms treated with LBS-assisted coil embolization were evaluated. Researchers reviewed TOF MRA and CE MRA images in terms of occlusion and stent patency. Aneurysm occlusion was graded according to Raymond-Roy classification as follows: total occlusion (grade 1), residual neck (grade 2), and residual aneurysm (grade 3). Stent patency was scored as follows: occlusion (1), stenosis (2), and normal (3). Interobserver and intermodality agreement values were determined by weighted kappa (κ) statistics.

RESULTS

Intermodality and interobserver values of TOF MRA and CE MRA with digital subtraction angiography (DSA) were perfect (κ = 1.00, p < 0.001) in terms of aneurysm occlusion. Rate of stent occlusion and stenosis in DSA, TOF, and MRA, respectively, were as follows: 0 and 12.5%, 16.6 and 70.8%, and 0 and 62.5%. Intermodality agreement values of TOF MRA and CE MRA with DSA were insignificant in terms of stent patency (κ = 0.065, p = 0.27; κ = 0.158, p = 0.15, respectively). Interobserver agreement was substantial in both TOF MRA (κ = 0.71, p < 0.001) and CE MRA (κ = 0.64, p = 0.001).

CONCLUSIONS

Both TOF and CE MRA techniques have strong concordance with DSA for the detection of aneurysm occlusion status. CE MRA can be used as a first-line noninvasive imaging modality due to its superiority to TOF MRA with respect to the visualization of in-stent signals.

Non-Contrast-Enhanced Silent Scan MR Angiography of Intracranial Anterior Circulation Aneurysms Treated with a Low-Profile Visualized Intraluminal Support Device

BACKGROUND AND PURPOSE

The Low-Profile Visualized Intraluminal Support Device comprises a small-cell nitinol structure and a single-wire braided stent that provides greater metal coverage than previously reported intracranial stents, as well as assumed strong susceptibility artifacts. This study aimed to assess the benefits of non-contrast-enhanced MRA by using a Silent Scan (Silent MRA) for intracranial anterior circulation aneurysms treated with Low-Profile Visualized Intraluminal Support Device stents.

MATERIALS AND METHODS

Thirty-one aneurysms treated with Low-Profile Visualized Intraluminal Support Device stents were assessed by using Silent MRA, 3D TOF-MRA, and x-ray DSA. The quality of MRA visualization of the reconstructed artery was graded on a 4-point scale from 1 (not visible) to 4 (excellent). Aneurysm occlusion status was evaluated by using a 2-grade scale (total occlusion/remnant [neck or aneurysm]). Weighted κ statistics were used to evaluate interobserver and intermodality agreement.

RESULTS

The mean scores ± SDs for Silent MRA and 3D TOF-MRA were 3.16 ± 0.79 and 1.48 ± 0.67 (P < .05), respectively, with substantial interobserver agreement (κ = 0.66). The aneurysm occlusion rates of the 2-grade scale (total occlusion/remnant [neck or aneurysm]) were 69%/31% for DSA, 65%/35% for Silent MRA, and 92%/8% for 3D TOF-MRA, respectively. The intermodality agreements were 0.88 and 0.30 for DSA/Silent MRA and DSA/3D TOF-MRA, respectively.

CONCLUSIONS

Silent MRA seems to be useful for visualizing intracranial anterior circulation aneurysms treated with Low-Profile Visualized Intraluminal Support Device stents.

Follow-up assessment of coiled intracranial aneurysms using zTE MRA as compared with TOF MRA: a preliminary image quality study

OBJECTIVES

To prospectively assess coiled intracranial aneurysms using a novel non-contrast enhanced zero echo time (zTE) MR angiography (MRA) method, and compare its image quality with time-of-flight (TOF) MRA, using digital subtraction angiography (DSA) as reference.

METHODS

Twenty-five patients (10 males and 15 females; age 53.96 ± 12.46 years) were enrolled in this monocentric study. MRA sequences were performed 24 h before DSA. Susceptibility artefact intensity and flow signal within the parent artery were carried out using a 4-point scale. Occlusion status was assessed using the 3-grade Montreal scale.

RESULTS

Scores of zTE were higher than TOF for both susceptibility artefact intensity (3.42 ± 0.64, 2.92 ± 0.63, P = 0.01) and flow signal (3.66 ± 0.95, 3.24 ± 1.24, P = 0.01). DSA revealed 17 complete occlusions, five residual neck aneurysms and two residual aneurysms. Inter-observer agreement was excellent (weighted κ: 0.89) for zTE and good (weighted κ: 0.68) for TOF. Intermodality agreement was excellent for zTE (weighted κ: 0.95) and good for TOF (weighted κ: 0.80). Correlations of both MRA sequences with DSA were high (zTE, Spearman's ρ: 0.91; TOF, Spearman's ρ: 0.81).

CONCLUSIONS

zTE MRA showed promising results for follow-up assessment of coiled intracranial aneurysms and was superior to TOF MRA for visualizing the parent artery and evaluating occlusion status.

KEY POINTS

• Various MRA sequences were applied for follow-up assessment of coiled intracranial aneurysms. • zTE MRA was less sensitive to susceptibility artefacts and haemodynamics. • In this monocentric study, zTE MRA was equivalent to DSA. • zTE MRA maybe an alternative to TOF MRA for follow-up assessment.

Usefulness of Non-Contrast-Enhanced MR Angiography Using a Silent Scan for Follow-Up after Y-Configuration Stent-Assisted Coil Embolization for Basilar Tip Aneurysms

BACKGROUND AND PURPOSE

Y-configuration stent-assisted coil embolization is used for treating wide-neck aneurysms. Noninvasive alternatives to x-ray DSA for follow-up after Y-configuration stent-assisted coil embolization treatment are required. This study aimed to assess the usefulness of non-contrast-enhanced MRA by using a Silent Scan (silent MRA) for follow-up after Y-configuration stent-assisted coil embolization for basilar tip aneurysms.

MATERIALS AND METHODS

Seven patients treated with Y-configuration stent-assisted coil embolization for basilar tip aneurysms underwent silent MRA, 3D TOF-MRA, and DSA. Silent MRA and 3D TOF-MRA images were obtained during the same scan session on a 3T MR imaging system. Two neuroradiologists independently reviewed both types of MRA images and subjectively scored the flow in the stents on a scale of 1 (not visible) to 5 (nearly equal to DSA) by referring to the latest DSA image as a criterion standard. Furthermore, we evaluated the visualization of the neck remnant.

RESULTS

In all patients, the 2 observers gave a higher score for the flow in the stents on silent MRA than on 3D TOF-MRA. The average score ± standard deviation was 4.07 ± 0.70 for silent MRA and 1.93 ± 0.80 (P < .05) for 3D TOF-MRA. Neck remnants were depicted by DSA in 5 patients. In silent MRA, neck remnants were depicted in 5 patients, and visualization was similar to DSA; however, in 3D TOF-MRA, neck remnants were depicted in only 1 patient.

CONCLUSIONS

Silent MRA might be useful for follow-up after Y-configuration stent-assisted coil embolization.

A Comparison of Magnetic Resonance Angiography Techniques for the Evaluation of Intracranial Aneurysms Treated With Stent-assisted Coil Embolization

AIM

To identify the effective magnetic resonance angiography (MRA) technique to monitor intracranial aneurysms treated with stent-assisted coiling.

MATERIALS AND METHODS

Retrospective analysis of various MRA techniques was performed in 42 patients. Three neuroradiologists independently compared non-contrast time of flight (ncTOF) MRA of the head, contrast-enhanced time of flight (cTOF) MRA of the head and dynamic contrast-enhanced MRA (CEMRA) of the head and neck or of the head. Digital subtraction angiography (DSA) was available for comparison in 32 cases. Inter-rater agreement (kappa statistic) was assessed.

RESULTS

Artifactual in-stent severe stenosis or flow gap was identified by ncTOF MRA in 23 of 42 cases (55%) and by cTOF MRA in 23 of 38 cases (60%). DSA excluded in-stent stenosis or occlusion in all 32 cases. No difference was noted between ncTOF and cTOF in the demonstration of neck remnants or residual aneurysms in three cases each. CEMRA of the head and neck or of the head was rated superior to ncTOF and cTOF MRA by all three investigators in seven out of eight cases. In one case, all three techniques demonstrated signifcant artifacts due to double stent placement during coiling. The kappa statistic revealed 0.8 agreement between investigators.

CONCLUSIONS

In the assessment of stent-assisted coiling of intracranial aneurysm, both ncTOF and cTOF MRA show similar results. CEMRA tends to show better flow signals in stent and residual aneurysm.

Stability of Cerebral Aneurysms After Stent-Assisted Coil Embolization

BACKGROUND:

The availability of stents has widened the indications of endovascular intervention for cerebral aneurysms.

OBJECTIVE:

To elucidate the effect of stents on radiologic outcomes and to analyze the risk factors for aneurysmal recanalization via propensity score matching.

METHODS:

From the 735 aneurysms treated with coil embolization with stents (n = 187) and without stents (n = 548) between 2009 and 2011, 157 propensity score-matched case pairs were selected. The recanalization rates and relevant risk factors were analyzed. The mean follow-up interval was 24.1 ± 11.3 months (range, 6-48 months) and 22.9 ± 11.4 months (range, 6-56 months) in the stent and nonstent groups, respectively (P = .388).

RESULTS:

The stent group demonstrated lower recanalization rates than the nonstent group during both the 6-month (1.9% vs 10.2%, P = .004) and the final follow-up periods (8.3% vs 18.5%, P = .005). The multivariate analysis identified the following significant factors for recanalization: the use of stents (hazard ratio, 0.40; 95% confidence interval, 0.21-0.76, P = .005), larger aneurysm size (hazard ratio, 1.21; 95% confidence interval, 1.11-1.31, P &lt; .001), and initially incomplete occlusion (hazard ratio, 2.39; 95% confidence interval, 1.28-4.43, P = .006). The incidence of permanent neurological complication tended to be higher in the stent group than in the nonstent group (3.2% vs 0%, P = .063).

CONCLUSION:

In this propensity score-matched analysis, stent implantation reduced the overall recanalization of the coiled cerebral aneurysms. However, the use of stents should be carefully decided upon.

Concurrent use of the Pipeline Embolization Device and coils for intracranial aneurysms: technique, safety, and efficacy

OBJECT

The use of the Pipeline Embolization Device (PED) as a sole endovascular modality has been described for the treatment of brain aneurysms. The benefit of using coils concurrently with a limited number of PEDs is not well documented. The authors describe their experience with this technique as well as their midterm clinical and angiographic results.

METHODS

This is a retrospective review of patients treated between 2011 and 2014. The authors placed a minimal number of PEDs with the addition of coils using a "jailed" microcatheter technique. A partially dense coil mass was obtained. Immediate and midterm clinical and angiographic results are reviewed.

RESULTS

The authors treated 27 patients harboring 28 aneurysms using this technique. The mean aneurysm size was 11.9 mm, and the mean neck size was 5.4 mm. A mean of 1.48 PEDs were placed per patient, and a mean of 1.33 PEDs per aneurysm were placed. The Raymond score immediately after PED placement was 2 or 3 in 82.1% of the patients. There were no intraprocedural or postprocedural complications. All PEDs were successfully deployed. No clinical or technical adverse effects related to the coil mass were observed. There were no clinical or radiographic signs of ischemia in this group. At follow-up imaging, complete aneurysm occlusion was demonstrated on the first MR angiogram (3-5 months) in all patients who reached this milestone. Follow-up digital subtraction angiography (5-13 months) confirmed complete occlusion in all patients who reached this milestone. All patients maintained their baseline clinical status.

CONCLUSIONS

The deployment of PEDs with concurrent partially dense coiling is safe and efficacious. This technique achieved early complete occlusion and endovascular reconstruction of the parent vessel, without inducing mass effect. Favorable midterm clinical results were observed in all patients.

Assessing Blood Flow in an Intracranial Stent: A Feasibility Study of MR Angiography Using a Silent Scan after Stent-Assisted Coil Embolization for Anterior Circulation Aneurysms

BACKGROUND AND PURPOSE

Blood flow in an intracranial stent cannot be visualized with 3D time-of-flight MR angiography owing to magnetic susceptibility and radiofrequency shielding. As a novel follow-up tool after stent-assisted coil embolization, we applied MRA by using a Silent Scan algorithm that contains an ultrashort TE combined with an arterial spin-labeling technique (Silent MRA). The purpose of this study was to determine whether Silent MRA could visualize flow in an intracranial stent placed in the anterior circulation.

MATERIALS AND METHODS

Nine patients treated with stent-assisted coil embolization for anterior circulation aneurysms underwent MRAs (Silent MRA and TOF MRA) and x-ray digital subtraction angiography. MRAs were performed in the same session on a 3T unit. Two neuroradiologists independently reviewed the MRA images and subjectively scored flow in a stent as 1 (not visible) to 4 (excellent) by referring to the latest x-ray digital subtraction angiography image as a criterion standard.

RESULTS

Both observers gave MRA higher scores than TOF MRA for flow in a stent in all cases. The mean score for Silent MRA was 3.44 ± 0.53, and for TOF MRA, it was 1.44 ± 0.46 (P < .001).

CONCLUSIONS

Silent MRA was able to visualize flow in an intracranial stent more effectively than TOF MRA. Silent MRA might be useful for follow-up imaging after stent-assisted coil embolization, though these study results may be only preliminary due to some limitations.

Optimized angiographic CT using intravenous contrast injection: a noninvasive imaging option for the follow-up of coiled aneurysms?

BACKGROUND AND PURPOSE

Because recanalization of coiled cerebral aneurysms is reported to occur, follow-up imaging is mandatory, ideally noninvasively. Our study aimed to evaluate the accuracy of an optimized angiographic CT by using intravenous contrast material injection in the assessment of coiled cerebral aneurysms, compared with MR angiography and digital subtraction angiography, the criterion standard.

MATERIALS AND METHODS

We included 69 patients with 76 coiled cerebral aneurysms. In each patient, we performed an angiographic CT with intravenous contrast material injection with a dual rotational acquisition, a time-of-flight MR angiography, and a DSA. The angiographic CT with intravenous contrast material injection data was postprocessed by using newly implemented reconstructions modes and a dual-volume technique. An aneurysm occlusion rate was assessed in angiographic CT with intravenous contrast material injection and MRA; remnants were measured and correlated with DSA, respectively.

RESULTS

Twenty-eight remnants were revealed by DSA with a mean size of 3.1 × 3.1 mm. Angiographic CT with intravenous contrast material injection demonstrated a sensitivity of 93% and a specificity of 96% in remnant detection. MRA showed almost identical accuracy (sensitivity of 93%, specificity of 100%). Assessment of remnant size by angiographic CT with intravenous contrast material injection and by MRA revealed a high significant correlation with DSA, respectively (P < .001).

CONCLUSIONS

Optimized angiographic CT with intravenous contrast material injection and MRA demonstrated accuracy comparable with that of DSA in the follow-up of coiled aneurysms, respectively. The assessment of remnant size showed a high correlation with DSA for both techniques. Due to the lack of radiation exposure, MRA seems to be the preferred technique. However, angiographic CT with intravenous contrast material injection can be considered a reliable, noninvasive alternative in patients with MR imaging contraindications or in cases of compromising artifacts due to metal implants (ie, clips).

Detection and characterization of unruptured intracranial aneurysms: Comparison of 3T MRA and DSA

PURPOSE

To compare magnetic resonance angiography (MRA) at 3 Tesla (3T) and digital subtraction angiography (DSA) for the detection and characterization of unruptured intracranial aneurysms (UIA).

MATERIALS AND METHODS

This study has been approved by our local ethical committee. From February to August 2010, 40 consecutive patients with UIA contemporarily underwent MRA at 3T including time-of-flight (TOF-MRA) and contrast enhanced (CE-MRA) techniques and DSA. MR images were independently reviewed by 3 radiologists and DSA images were reviewed by 2 radiologists together. Interobserver and intertechnique agreements were assessed for aneurysm detection and characterization including maximal diameter, neck width and the presence of a bleb or a branch arising from the sac.

RESULTS

DS angiography revealed 56 aneurysms. Mean sensitivity and positive predictive value of MRA were 91.4% and 93.4% respectively. For UIA < 3 mm and those ≥ 3 mm, MRA had a mean sensitivity of 74.1% and 100% respectively. Intertechnique and interobserver agreements were substantial for the measurement of UIA maximal diameter (mean κ, 0.607 and 0.601 respectively) and were moderate and fair for neck width measurement respectively (mean κ, 0.456 and 0.285 respectively). For bleb detection, intertechnique and interobserver agreements were fair and slight respectively (mean κ, 0.312 and 0.116 respectively) whereas both were slight for detection of branches arising from the sac (mean κ, 0.151 and 0.070 respectively).

CONCLUSION

MR angiography at 3T has a high sensitivity for the detection of UIA. However, it remains significantly inferior to DSA for morphological characterization of UIA.