Aneurysm wall enhancement, hemodynamics, and morphology of intracranial fusiform 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.

Vessel wall enhancement in vertebrobasilar dolichoectasia is associated with posterior circulation infarction: An observational study based on high-resolution magnetic resonance imaging

BACKGROUND

Posterior circulation infarction (PCI) is the most common manifestation of vertebrobasilar dolichoectasia (VBD). Vessel wall enhancement (VWE) in high-resolution magnetic resonance imaging (HR-MRI) is associated with ischemic stroke.

OBJECTIVES

This study aims to evaluate different quantitative VWE parameters in identifying PCI in VBD patients by comparing the sensitivity of each VWE parameter. The associated factors of PCI and VWE were also identified.

METHODS

Patients with VBD who received HR-MRI were retrospectively analyzed and divided into PCI and non-PCI groups. Morphological parameters of VBD were measured using magnetic resonance angiography. VWE parameters, including arterial-to-pituitary stalk contrast ratio (CRstalk), arterial enhancement index, and arterial enhancement ratio, were extracted and calculated. The receiver-operating characteristic curve was used to compare the sensitivity of VWE parameters in discriminating PCI. The independent factors associated with PCI and VWE were investigated.

RESULTS

A total of 140 patients with VBD were included. Forty patients (28.6 %) had PCI. CRstalk with the average signal intensity (CRstalk-avg) had the highest sensitivity in identifying PCI with an area under curve value of 0.783 and a cut-off value of 0.47. CRstalk-avg (OR = 2.908, p < 0.001) and basilar artery tortuosity index (BATI) (OR = 1.391, p = 0.033) were independently associated with PCI. The independent associated factors of VWE were BA diameter (OR = 4.273, p < 0.001), BATI (OR = 1.040, p = 0.032), and hyperlipidemia (OR = 3.040, p = 0.018).

CONCLUSION

CRstalk-avg may be the most sensitive parameter for quantifying VWE to identify PCI in patients with VBD, and it is also independently associated with PCI. BA diameter, BATI, and hyperlipidemia are independently associated with VWE.

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.

Systematic evaluation of neuro-ophthalmic outcomes of the ophthalmic artery covered by flow-diverter

Carotid-ophthalmic aneurysms (COA) are complex and severe intracranial arterial lesions, and their treatment and management have always been a focus of clinical research. In recent years, the introduction of flow diverters (FD) has provided a revolutionary method for the treatment of intracranial aneurysms (IA). Although FD has achieved significant success in reducing the risk of COA rupture, the complex anatomical structure and critical function of the ophthalmic artery (OphA) mean that covering the OphA with FD may lead to adverse ophthalmic outcomes. This review aims to systematically examine the ocular complications and their mechanisms when FD covers the OphA in the treatment of COA, emphasizing the potential risks that clinicians should be aware of when applying FD treatment, to reduce complications and improve the overall prognosis of patients.

Computational fluid dynamics analysis for predicting microaneurysm formation in parent arteries of unruptured cerebral aneurysms: implications for neck clipping safety

Background

Aneurysmal subarachnoid hemorrhage caused by cerebral aneurysm rupture has a poor prognosis, with mortality exceeding 30% despite treatment advancements. Surgical neck clipping remains the standard for preventing rupture, but intraoperative rupture rates vary significantly (3-50%) and are influenced by vascular complexity and technical challenges. Thinning of the vascular wall near the aneurysm neck, particularly with microaneurysm formation, has emerged as a significant risk factor, yet these changes often go undetected in preoperative imaging.

Objective

This study aimed to evaluate the utility of computational fluid dynamics (CFD) analysis for predicting microaneurysm formation in the parent artery adjacent to unruptured cerebral aneurysms, using the parent artery radiation sign (PARS) as a predictive marker.

Methods

We conducted a single-center, retrospective observational study of 89 patients with unruptured middle cerebral artery (MCA) aneurysms treated with neck clipping from May 2020 to April 2022. Based on preoperative three-dimensional computed tomography angiography (3D-CTA), CFD analysis identified PARS through specific hemodynamic indicators. Intraoperative findings were analyzed and compared between PARS-positive and PARS-negative groups. The sensitivity and specificity of PARS for predicting microaneurysm formation were investigated.

Results

Of the 87 aneurysms analyzed, 25 (28.7%) were PARS-positive, and 62 (71.3%) were PARS-negative. Microaneurysms were identified intraoperatively in nine cases, eight of which were in the PARS-positive group. The sensitivity and specificity of PARS for detecting microaneurysms were 89 and 78%, respectively. The positive likelihood ratio was 4.1, while the negative likelihood ratio was 0.142.

Conclusion

CFD analysis using PARS offers a reliable method for predicting microaneurysm formation in the parent artery, potentially guiding surgical planning and reducing intraoperative rupture risk. While promising, these findings are limited by the retrospective, single-center design, highlighting the need for further research in larger, multicenter cohorts. Incorporating CFD analysis into preoperative assessment could significantly enhance the safety and outcomes of neck clipping procedures for unruptured cerebral aneurysms.

High-resolution magnetic resonance vessel wall imaging provides new insights into Moyamoya disease

Moyamoya disease (MMD) is a rare condition that affects the blood vessels of the central nervous system. This cerebrovascular disease is characterized by progressive narrowing and blockage of the internal carotid, middle cerebral, and anterior cerebral arteries, which results in the formation of a compensatory fragile vascular network. Currently, digital subtraction angiography (DSA) is considered the gold standard in diagnosing MMD. However, this diagnostic technique is invasive and may not be suitable for all patients. Hence, non-invasive imaging methods such as computed tomography angiography (CTA) and magnetic resonance angiography (MRA) are often used. However, these methods may have less reliable diagnostic results. Therefore, High-Resolution Magnetic Resonance Vessel Wall Imaging (HR-VWI) has emerged as the most accurate method for observing and analyzing arterial wall structure. It enhances the resolution of arterial walls and enables quantitative and qualitative analysis of plaque, facilitating the identification of atherosclerotic lesions, vascular entrapment, myofibrillar dysplasia, moyamoya vasculopathy, and other related conditions. Consequently, HR-VWI provides a new and more reliable evaluation criterion for diagnosing vascular lesions in patients with Moyamoya disease.

A hemodynamic analysis of energy loss in abdominal aortic aneurysm using three-dimension idealized model

Objective: The aim of this study is to perform specific hemodynamic simulations of idealized abdominal aortic aneurysm (AAA) models with different diameters, curvatures and eccentricities and evaluate the risk of thrombosis and aneurysm rupture. Methods: Nine idealized AAA models with different diameters (3 cm or 5 cm), curvatures (0° or 30°) and eccentricities (centered on or tangent to the aorta), as well as a normal model, were constructed using commercial software (Solidworks; Dassault Systemes S.A, Suresnes, France). Hemodynamic simulations were conducted with the same time-varying volumetric flow rate extracted from the literature and 3-element Windkessel model (3 EWM) boundary conditions were applied at the aortic outlet. Several hemodynamic parameters such as time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), relative residence time (RRT), endothelial cell activation potential (ECAP) and energy loss (EL) were obtained to evaluate the risk of thrombosis and aneurysm rupture under different conditions. Results: Simulation results showed that the proportion of low TAWSS region and high OSI region increases with the rising of aneurysm diameter, whereas decreases in the curvature and eccentric models of the corresponding diameters, with the 5 cm normal model having the largest low TAWSS region (68.5%) and high OSI region (40%). Similar to the results of TAWSS and OSI, the high ECAP and high RRT areas were largest in the 5 cm normal model, with the highest wall-averaged value (RRT: 5.18 s, ECAP: 4.36 Pa-1). Differently, the increase of aneurysm diameter, curvature, and eccentricity all lead to the increase of mean flow EL and turbulent EL, such that the highest mean flow EL (0.82 W · 10-3) and turbulent EL (1.72 W · 10-3) were observed in the eccentric 5 cm model with the bending angle of 30°. Conclusion: Collectively, increases in aneurysm diameter, curvature, and eccentricity all raise mean flow EL and turbulent flow EL, which may aggravate the damage and disturbance of flow in aneurysm. In addition, it can be inferred by conventional parameters (TAWSS, OSI, RRT and ECAP) that the increase of aneurysm diameter may raise the risk of thrombosis, whereas the curvature and eccentricity appeared to have a protective effect against thrombosis.