Wall enhancement ratio determined by vessel wall MRI associated with symptomatic intracranial aneurysms

Association of wall enhancement on high-resolution magnetic resonance imaging with morphology and hemodynamics in unruptured intracranial aneurysms

OBJECTIVE

To investigate the relationships between intracranial aneurysm (IA) wall enhancement (AWE) and aneurysm morphology and hemodynamic parameters.

METHODS

A total of 100 patients (112 unruptured aneurysms) were categorized by enhancement degree (significant, slight, no enhancement) and pattern (circumferential, partial, no enhancement). Morphological and AWE features were measured using enhanced high-resolution magnetic resonance images (HR-MRI). Computational fluid dynamics (CFD) was used to calculate hemodynamic parameters, including time-averaged wall shear stress (TAWSS), normalized time-averaged wall shear stress (NTAWSS), oscillatory shear index (OSI), gradient oscillatory number (GON), and relative residence time (RRT).

RESULTS

NTAWSS (p < 0.05), aspect ratio (AR, p < 0.01), and size ratio (SR, p < 0.01) showed significantly statistical difference among AWE groups. The significantly enhanced group had higher AR and SR and higher RRT but lower NTAWSS compared to non-enhanced and slightly enhanced groups. Enhancement ratio negatively correlated with NTAWSS (rs = -0.33, p < 0.001), OSI (rs = -0.28, p = 0.003), and positively correlated with the GON (rs = 0.22, p = 0.018) and RRT (rs = 0.31, p < 0.001) and SR (rs = 0.51, p < 0.001) and AR (rs = 0.48, p < 0.001).

CONCLUSION

Aneurysmal morphological and hemodynamic features are related to the degree and extent of AWE. Unruptured IAs with more intense AWE are larger and have lower NTAWSS and higher RRT.

There Is Poor Agreement between the Subjective and Quantitative Adjudication of Aneurysm Wall Enhancement

BACKGROUND AND PURPOSE

The determination of aneurysm wall enhancement (AWE) by human readers on visual inspection alone is subjective and prone to error. A 3D method for quantifying the signal intensity (SI) of the aneurysm enables objective determination of AWE. Interreader agreement and agreement between subjective and objective determination of AWE were assessed in this study.

MATERIALS AND METHODS

Patients with saccular intracranial aneurysms (IAs) were imaged with high-resolution MRI. In the subjective assessment, 2 internal adjudicators visually determined AWE if the degree of enhancement was equal to or higher than that of the pituitary stalk. An experienced internal neuroradiologist resolved disagreements. This internal adjudication was compared with an external adjudication to assess interrater agreement among centers. In the objective assessment, the distribution of SI across the aneurysm wall after normalizing the SI to the corpus callosum was determined with an in-house code. The normalized mean SI on postcontrast T1 MRI was defined as 3D-circumferential AWE (3D-CAWE). If the 3D-CAWE value was higher than 1, an IA was defined as objectively "enhancing." Interrater agreement was analyzed with κ coefficients. Intertechnique agreement between the subjective and objective assessments was performed using κ statistics. Univariate regressions were used to identify which morphologic characteristics influenced subjective adjudication of enhancement.

RESULTS

A total of 113 IAs were analyzed. The agreement of the internal assessment was moderate (κ = 0.63), 49.5% of IAs (56) were classified as "enhancing;" and 50.5% (57) as "nonenhancing" after consensus. Interrater agreement between internal and external adjudication was weak (κ = 0.52) for the presence of AWE. There was no agreement between the subjective assessment of AWE and objective 3D-CAWE (κ = 0.16, P = .02). Subjective assessment was less likely to reliably adjudicate enhancement when assessing multiple aneurysms (OR, 0.4; 95% CI, 0.16-0.97; P = .04) and IAs larger than >7 mm (OR, 0.22; 95% CI, 0.09-0.55; P = .002) despite being objectively nonenhancing.

CONCLUSIONS

Subjective adjudication of AWE has poor interrater agreement, and no agreement with an objective 3D method of determining AWE. It is also less likely than objective quantification to identify enhancement in aneurysms of >7 mm or when multiple aneurysms are present. Objective 3D quantification, such as the technique used in this study, should, therefore, be considered when assessing AWE, especially in patients with multiple aneurysms and aneurysms of >7 mm in size.

Combined Susceptibility-Weighted Imaging and Vessel Wall Imaging of Unruptured Intracranial Aneurysms Presenting with Sentinel Headache

BACKGROUND

The combinational assessment of susceptibility-weighted imaging and vessel wall imaging on magnetic resonance imaging (MRI) in patients of unruptured intracranial aneurysms presenting with sentinel headache can show microbleeds and inflammatory changes in the wall of the aneurysms and thus predict the future risk of rupture of the aneurysm. In this pilot study, we hypothesized that combination of vessel wall imaging and susceptibility-weighted imaging would be more informative to assess the changes in the wall of aneurysm in patients with sentinel headache.

MATERIALS AND METHODS

Fifteen patients of intracranial aneurysms with history of sentinel headache underwent advanced MRI. Susceptibility-weighted imaging images were evaluated for presence of any hypointensity suggestive of microbleeds along the wall of the aneurysm. The postcontrast vessel wall images were evaluated for presence of any wall enhancement.

RESULTS

Susceptibility foci suggestive of microbleeds on susceptibility-weighted imaging in the wall of the aneurysms were seen in 14 intracranial aneurysms. Vessel wall imaging showed enhancement of wall in 10 cases and nonenhancement in five cases. Enhancement of the wall on MRI was observed more in aneurysms imaged early after the onset of symptoms (<45 days) than in those imaged late (>45 days).

CONCLUSION

Our observations might be indicative of temporally evolving pathologic changes in the aneurysmal wall in unruptured aneurysms with sentinel headache. Combining advanced magnetic resonance sequences can help in elucidation of the wall pathology and rupture risk assessment of unruptured aneurysms, and these observations could be incorporated in future studies.

The relationship between symptomatic status and aneurysm wall enhancement characteristics of single unruptured intracranial aneurysm

OBJECTIVE

We aimed to analyze the aneurysm wall enhancement (AWE) characteristics of a single unruptured intracranial aneurysm (UIA) and observe the relationship between the symptoms of a single UIA and the aneurysm wall.

METHODS

In our hospital, 85 patients diagnosed with a single UIA using computed tomography angiography (CTA) were retrospectively analyzed. The patients were divided into symptomatic and asymptomatic groups, including 46 asymptomatic and 39 symptomatic aneurysms. High-resolution magnetic resonance imaging of the vascular wall (HR-MR-VWI) was utilized to ascertain the presence, degree, and extent of AWE and thick-wall enhancement. In addition to AWE characteristics, morphological parameters of aneurysms, such as maximal size, shape, height, neck width, aspect ratio (AR), and size ratio (SR), were scanned using CTA. The differences in the parameters of a single UIA between the two groups were compared. An investigation explored the correlation between the symptom status of a single UIA and AWE.

RESULTS

We observed a correlation between symptom status and maximal size, height, and neck width for a single UIA, the presence or absence of AWE, and the levels and boundaries of AWE and thick-wall reinforcement. This study found that the AWE range was independently correlated with symptom status in the multivariate regression analysis.

CONCLUSION

A larger AWE range was an independent risk factor for the onset of symptoms in a single UIA.

Vessel wall imaging and quantitative flow assessment in arteriovenous malformations: A feasibility study

INTRODUCTION

Cerebral arteriovenous malformations (AVMs) carry a rupture rate of 2-3% per year. Several architectural factors may influence rupture rate, and a recently theorized model of AVMs describes the influence of vessel wall inflammation. A novel imaging modality, vessel wall imaging (VWI), has been developed to view inflammatory processes in vessel wall foci but has not yet been examined in AVMs, which is the aim of this study.

METHODS

This retrospective review studies prospectively collected data on patients with ruptured and unruptured AVMs between 2019 and 2021. Inclusion criteria included adult patients (≥18 years) with radiographically diagnosed AVM who underwent VWI. Charts were reviewed for medical history, clinical presentation, hospital course, discharge condition, and follow-up. Angioarchitectural features, blood flow, and VWI were compared in patients with and without hemorrhagic patients.

RESULTS

Nine patients underwent VWI, mean age 37.7 ± 9.9 years. Four presented with hemorrhage (44.4%). Seven (77.7%) received glue embolization and 6 (66.7%) underwent surgical resection. All patients (4/4) with a history of hypertension presented with hemorrhage (p = 0.0027). Size and Spetzler-Martin grade were not associated with hemorrhage (p = 0.47, p = 0.59). Net AVM flow was higher in patients presenting with hemorrhage, although nonsignificant (p = 0.19). With VWI, 3 (75%) hemorrhagic AVMs showed visible nidus and draining veins, and all three demonstrated positive post-contrast wall enhancement in at least one of their draining veins; conversely, of fivenonhemorrhagic AVMs, only 2 (40%) demonstrated post-contrast wall enhancement in any draining vein (p = 0.090).

CONCLUSION

This pilot study successfully demonstrated capture of venous walls in AVMs using VWI. In this study, draining vein enhancement occurred more often in hemorrhagic AVM and in those with higher venous volumetric flow.

Does it stable? Intracranial aneurysm wall enhancement might be the warning signals: a meta-analysis of observational studies

Magnetic resonance vessel wall imaging (MR-VWI) is an emerging imaging technology used to assess the progressive risk of unruptured intracranial aneurysms (UIAs). Unlike the standard evaluation model, MR-VWI is still debatable. This study aims to further define the potential relationship between aneurysm wall enhancement (AWE) and aneurysm stability. Using "intracranial aneurysm", "magnetic resonance", and "enhancement" as keywords, relevant studies were systematically searched in PubMed, Embase, and Cochrane, and the qualified studies were enrolled for further analysis. There were 13 case-control studies, 4 cohort studies, and 2,678 cases of intracranial aneurysms included in the meta-analysis. It was shown that AWE was correlated with intracranial aneurysm rupture (OR = 35.90, 95% CI: 15.58 to 82.75, p < 0.001), growth (OR = 6.69, 95% CI: 2.69 to 16.63, p < 0.001), and presence of symptoms (OR = 14.46, 95% CI: 9.07 to 23.05, p < 0.001). This finding had a high diagnostic value, but the correlation was probably not independent of aneurysm size. The pooled relative risks of the follow-up studies revealed that the risk of UIA progression was approximately 3.33 times higher with AWE than without AWE (RR = 3.33, 95% CI: 2.33 to 4.78, p < 0.001). In addition, the pooled results demonstrated that quantitative indices of VWI enhancement were equally linked with aneurysm stability (OR = 19.61, 95% CI: 10.63 to 36.17, p < 0.001). AWE is an effective imaging method to assess the stability of UIAs, and it can be a marker for the prophylactic treatment of small unruptured intracranial aneurysms in the future, which remains to be validated by prospective studies with large samples.

Neutrophil-to-lymphocyte ratio associated with symptomatic saccular unruptured intracranial aneurysm

BACKGROUND AND PURPOSE

Whether symptomatic unruptured intracranial aneurysms (UIAs) lead to change in circulating inflammation remains unclear. This study aims to evaluate the role of hematological inflammatory indicators in predicting symptomatic UIA.

METHODS

Adult patients diagnosed with saccular intracranial aneurysm from March 2019 to September 2023 were recruited retrospectively. Clinical and laboratory data, including the white blood cells (WBC), neutral counts (NEUT), lymphocyte counts (LYM), and monocyte counts (MONO) of each patient, were collected. The neutrophil-to-lymphocyte ratio (NLR) and lymphocyte-to-monocyte ratio (LMR) were calculated as NLR = NEUT/LYM, LMR = LYM/MONO, SII = PLT*NEUT/LYM. The hematological inflammatory indicators were compared in symptomatic saccular and asymptomatic UIA patients. Multivariable logistic regression analyses were performed to explore the factors predicting symptomatic UIA.

RESULTS

One hundred and fifty UIA patients with a mean age of 58.5 ± 12.4 were included, of which 68% were females. The NLR and LMR were significantly associated with symptomatic UIA, and the association remained in small UIAs (< 7 mm). The multiple logistic regression analysis showed that NLR was independently associated with symptomatic UIA. On ROC curve analysis, the optimal cutoff value of NLR to differentiate symptomatic from asymptomatic was 2.38. In addition, LMR was significantly associated with symptomatic UIA smaller than 7 mm.

CONCLUSION

There was a significant correlation between NLR and symptomatic UIA. The NLR was independently associated with symptomatic UIA.

Qualitative and quantitative wall enhancement associated with unstable intracranial aneurysms: a meta-analysis

Background

Unstable intracranial aneurysms (UIAs) are more likely to rupture and cause serious consequences. Evaluating the stability of unruptured aneurysms facilitates clinical management stratification.

Purpose

To compare and evaluate the predictive performance of qualitative and quantitative wall enhancement (aneurysmal wall enhancement [AWE], circumferential aneurysmal wall enhancement [CAWE], wall enhancement ratio [WER]) on high-resolution magnetic resonance imaging (MRI) of the vessel wall to predict the presence of UIA.

Material and Methods

Original articles describing the depiction of aneurysmal wall enhancement on 3.0-T or 1.5-T high-resolution vessel wall imaging were retrieved from the Web of Science, Medline/PubMed, the Cochrane Library, and EMBASE databases up to 15 February 2022. The combined sensitivity, specificity, and summary area under the receiver operating characteristic curve (AUC) were calculated, and meta-regression analysis was performed.

Results

In total, 12 original articles involving 1619 intracranial aneurysms (IAs) were included. The combined sensitivity and specificity of AWE, CAWE, and WER were 91% and 67%, 59% and 83%, and 86% and 75%, respectively, in the diagnosis of UIA. The summary AUC values of these items were, in order from high to low, 0.88 (WER), 0.84 (AWE), and 0.77 (CAWE), and the differences among them were significant ( z = 2.976, P = 0.003 and z = 2.950, P = 0.003). The meta-regression analysis identified average size and 2D/3D magnetic imaging technology as possible sources of heterogeneity.

Conclusion

Qualitative and quantitative wall enhancement showed moderate accuracy in predicting UIA, and WER had the highest accuracy among them in this meta-analysis. Two covariates were found to explain the heterogeneity.

Circumferential wall enhancement with contrast ratio measurement in unruptured intracranial aneurysm for aneurysm instability

BACKGROUND

Aneurysm wall enhancement on high-resolution vessel wall imaging (HR-VWI) may represent vessel wall inflammation for unruptured intracranial aneurysms (UIAs). Further evidence for the role of circumferential aneurysm wall enhancement (CAWE) in evaluating the instability of UIAs is required, especially in small aneurysms (<7 mm).

METHODS

We analyzed patients with saccular UIAs who prospectively underwent HR-VWI on a 3.0 T MRI scanner in our center from September 2017 to August 2021. The presence of AWE was identified and quantitatively measured using the aneurysm-to-pituitary stalk contrast ratio (CRstalk) with maximal signal intensity value. The PHASES and ELAPSS scores were used to assess the risk of aneurysm rupture and growth. We evaluated the association of CAWE and CRstalk value with intracranial aneurysm instability.

RESULTS

One hundred patients with 109 saccular UIAs were included in this study. Eighty-three UIAs (76.1%) had a size smaller than 7 mm. PHASES and ELAPSS scores were significantly higher in UIAs with CAWE than in UIAs without CAWE (p < .01). The association of CAWE with PHASES and ELAPSS scores remained in small UIAs (<7 mm). The optimal cutoff value of CRstalk for CAWE was 0.5. PHASES and ELAPSS scores were significantly higher in UIAs with CRstalk ≥0.5 than in UIAs with CRstalk <0.5 (p < .01).

CONCLUSIONS

CAWE on HR-VWI is a valuable imaging marker for aneurysm instability in UIAs. CRstalk value ≥0.5 may be associated with a higher risk of intracranial aneurysm rupture and growth.

Intracranial aneurysm wall enhancement as an indicator of instability: a systematic review and meta-analysis

BACKGROUND AND PURPOSE

Aneurysm wall enhancement (AWE) of intracranial aneurysms on magnetic resonance imaging has been described in previous studies as a surrogate marker of instability. With this study, an updated literature overview and summary risk estimates of the association between AWE and different specific outcomes (i.e., rupture, growth or symptomatic presentation) for both cross-sectional and longitudinal studies are provided.

METHODS

The PRISMA guideline was followed and a search was performed of PubMed and Embase to 1 January 2021 for studies that reported on AWE and aneurysm instability. In cross-sectional studies, AWE was compared between patients with stable and unstable aneurysms. In longitudinal studies, AWE of stable aneurysms was assessed at baseline after which patients were followed longitudinally. Risk ratios were calculated for longitudinal studies, prevalence ratios for cross-sectional studies and then the ratios were pooled in a random-effects meta-analysis. Also, the performance of AWE to differentiate between stable and unstable aneurysms was evaluated.

RESULTS

Twelve studies were included with a total of 1761 aneurysms. In cross-sectional studies, AWE was positively associated with rupture (prevalence ratio 11.47, 95% confidence interval [CI] 4.05-32.46) and growth or symptomatic presentation (prevalence ratio 4.62, 95% CI 2.85-7.49). Longitudinal studies demonstrated a positive association between AWE and growth or rupture (risk ratio 8.00, 95% CI 2.14-29.88). Assessment of the performance of AWE showed high sensitivities, mixed specificities, low positive predictive values and high negative predictive values.

CONCLUSIONS

Although AWE is positively associated with aneurysm instability, current evidence mostly supports the use of its absence as a surrogate marker of aneurysm stability.

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.

Objective quantification of contrast enhancement of unruptured intracranial aneurysms: a high-resolution vessel wall imaging validation study

OBJECTIVE

High-resolution vessel wall imaging (HR-VWI) has emerged as a valuable tool in assessing unruptured intracranial aneurysms (UIAs). There is no standardized method to quantify contrast enhancement of the aneurysm wall. Contrast enhancement can be objectively measured as signal intensity (SI) or subjectively adjudicated. In this study, the authors compared the different methods to quantify wall enhancement of UIAs and determined the sensitivity and specificity of each method as a surrogate of aneurysm instability. They also compared SI quantification between scanners from different manufacturers.

METHODS

The University of Iowa HR-VWI Project database was analyzed. This database compiles patients with UIAs who prospectively underwent HR-VWI using a 3T MRI scanner. The mean and maximal SI values of the aneurysm wall, pituitary stalk, and genu of the corpus callosum were used to compare 3 different measurement methods: 1) aneurysm enhancement ratio AER = (SIwall post - SIwall pre)/SIwall pre; 2) aneurysm-to-pituitary stalk contrast ratio CRstalk = SIwall post/SIstalk post; and 3) aneurysm enhancement index AEI = ([SIwall post/SIbrain post] - [SIwall pre/SIbrain pre])/(SIwall pre/SIbrain pre) (where "pre" indicates precontrast images and "post" indicates postcontrast images). Size ≥ 7 mm was used as a surrogate of aneurysm instability for receiver operating characteristic (ROC) curve analysis. To determine if the objective quantification of SI varies among scanners from different manufacturers, 9 UIAs underwent the same HR-VWI protocol using a 3T General Electric (GE) scanner and a 3T Siemens scanner. Three UIAs also underwent a third scanning procedure on a unit with a different magnet strength (7T GE).

RESULTS

Eighty patients with 102 UIAs were included in the study. The mean age was 64.5 ± 12.2 years, and 64 (80%) patients were women. UIAs ≥ 7 mm had significantly higher SIs than smaller UIAs (< 7 mm): AER = 0.82 vs 0.49, p < 0.001; CRstalk = 0.84 vs 0.61, p < 0.001; and AEI = 0.81 vs 0.48, p < 0.001. ROC curves demonstrated optimal sensitivity of 81.5% for CRstalk ≥ 0.60, 75.9% for AEI ≥ 0.50, and 74.1% for AER ≥ 0.49. Intermanufacturer correlation between 3T GE and 3T Siemens MRI scanners for CRstalk using mean and maximal SI values was excellent (Pearson coefficients > 0.80, p < 0.001). A similar correlation was identified among the 3 UIAs that underwent 7T imaging.

CONCLUSIONS

CRstalk using maximal SI values was the most reliable objective method to quantify enhancement of UIAs on HR-VWI. The same ratios were obtained between different manufacturers and on scans obtained using magnets of different strengths.

Basilar artery dissection with rupture 6 years after accidental detection: A case report

Background:

Chronic basilar artery dissection (BAD) is a rare pathology, and only a few reports have been mentioned in the literature. The imaging features of chronic BAD, especially those that develop into a subarachnoid hemorrhage (SAH), are unknown.

Case Description:

We report a unique case of a chronic BAD with a split intimal flap that developed into an SAH. A 74-year-old man was diagnosed with BAD. After considering all treatment options, conservative treatment was selected for the patient. We continued imaging follow-up of the patient in our outpatient clinic once a year. The BA gradually dilated and the internal flap split. The patient and his family refused surgical treatment; therefore, conservative treatment was continued. Six years and 2 months from the first diagnosis, he developed a massive SAH and died.

Conclusion:

In the case of this patient, the weakened condition of the internal elastic lamina may have caused dissection of the intimal flap between the intima and media. Furthermore, the dissection may have developed and connected the true lumen to the pseudolumen and induced BA rupture. Thereby, split of the internal flap could be a risk factor for rupture in chronic BAD.

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.

Lessons from Vessel Wall Imaging of Intracranial Aneurysms: New Era of Aneurysm Evaluation beyond Morphology

Recent basic studies have clarified that aneurysmal wall inflammation plays an important role in the pathophysiology of intracranial aneurysms. However, it remains an interdisciplinary challenge to visualize aneurysm wall status in vivo. MR-vessel wall imaging (VWI) is a current topic of advanced imaging techniques since it could provide an additional value for unruptured intracranial aneurysms (UIAs) risk stratification. With regard to ruptured intracranial aneurysms, VWI could identify a ruptured aneurysm in patients with multiple intracranial aneurysms. Intraluminal thrombus could be a clue to interpret aneurysm wall enhancement on VWI in ruptured intracranial aneurysms. The interpretation of VWI findings in UIAs would require much caution. Actually aneurysm wall enhancement in VWI was significantly associated with consensus morphologic risk factors. However, aneurysmal wall with contrast enhancement oftentimes associated with atherosclerotic, degenerated and thickened wall structure. It remains ill defined if thin wall without wall enhancement (oftentimes invisible in VWI) could be actually safe or look over wall vulnerability. We reviewed currently available studies, especially focusing on VWI for intracranial aneurysms and discussed the clinical utility of VWI.

Vessel wall imaging in intracranial aneurysms

High-resolution vessel wall imaging (HR-VWI) is becoming a useful tool in the characterization and identification of unstable unruptured brain aneurysms. However, it has not been validated for clinical use. The current evidence on HR-VWI techniques for characterization of brain aneurysms is described in this review. Specific imaging approaches such as aneurysm wall contrast enhancement, MRI-quantitative susceptibility mapping, and 7T MRI are described in detail.