Low Wall Shear Stress Is Associated with Local Aneurysm Wall Enhancement on High-Resolution MR Vessel Wall Imaging

Wang, Xiao; Qi, Tiewei; He, Shiliang; Li, Z.; Ou, San‐San; Zhang, G.; Liu, X.; Huang, Zheng; Liang, Fei

doi:10.3174/ajnr.a5806

Cited by 35 publications

(43 citation statements)

References 23 publications

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“…In this study, focal enhancement was colocalized with low AWSS, low maxOSI, and high LSA in agreement with results recently published by Xiao et al and Khan et al [13,31], confirming the assumption that enhanced regions possibly indicate the presence and localization of low-flow conditions in an aneurysm.…”

Section: Focal Enhancement Hemodynamic Parameters and Morphologysupporting

confidence: 93%

“…Focal enhancement has been reported to be associated with ruptured aneurysms and the rupture site [11,12]. While low-flow conditions near the aneurysm wall have been described to coincide with focal enhancement [13], low wall shear stress (WSS) has been found to be associated with rupture sites [14]. Other studies related flow characteristics, such as low shear area (LSA), shear concentration index (SCI), oscillatory shear index (OSI), neck inflow rate (NIR), inflow concentration index (ICI), and WSS to aneurysm growth, rupture risk, and rupture [15][16][17][18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

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Multimodal validation of focal enhancement in intracranial aneurysms as a surrogate marker for aneurysm instability

et al. 2020

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Purpose Circumferential enhancement on MR vessel wall imaging has been proposed as a biomarker of a higher risk of rupture in intracranial aneurysms. Focal enhancement is frequently encountered in unruptured aneurysms, but its implication for risk stratification and patient management remains unclear. This study investigates the association of focal wall enhancement with hemodynamic and morphological risk factors and histologic markers of wall inflammation and degeneration. Methods Patients with an unruptured middle cerebral artery aneurysm who underwent 3D rotational angiography and 3T MR vessel wall imaging showing focal wall enhancement were included. Hemodynamic parameters were calculated based on flow simulations and compared between enhanced regions and the entire aneurysm surface. Morphological parameters were semiautomatically extracted and quantitatively associated with wall enhancement. Histological analysis included detection of vasa vasorum, CD34, and myeloperoxidase staining in a subset of patients. Results Twenty-two aneurysms were analyzed. Enhanced regions were significantly associated with lower AWSS, lower maxOSI, and increased LSA. In multivariate analysis, higher ellipticity index was an independent predictor of wall enhancement. Histologic signs of inflammation and degeneration and higher PHASES score were significantly associated with focal enhancement. Conclusion Focal wall enhancement is colocalized with hemodynamic factors that have been related to a higher rupture risk. It is correlated with morphological factors linked to rupture risk, higher PHASES score, and histologic markers of wall destabilization. The results support the hypothesis that focal enhancement could serve as a surrogate marker for aneurysm instability.

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Section: Focal Enhancement Hemodynamic Parameters and Morphologysupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Multimodal validation of focal enhancement in intracranial aneurysms as a surrogate marker for aneurysm instability

et al. 2020

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“…According to previous studies, high or low wall shear stress (LWSS) may cause aneurysm formation. 1,3,4,18 The wall shear stress curve data supported the hypothesis that LWSS was a possible reason. Similar LWSS values also exist on the apexes of normal MCA bifurcations, however, the normal distribution of LWSS seldom causes aneurysms.…”

Section: Discussionsupporting

confidence: 64%

“…Previous studies offer some clues. 3,[18][19][20][21][22] Specifically, unlike the arterial wall, the apex of a cerebral arterial bifurcation lacks a tunica media and forms a "gap" that is filled with fibers from the tunica adventitia, namely the "apical ridge." This structure is composed of collagen fibers and can, therefore, bear stronger impingement of blood flow than the arterial wall.…”

Section: Discussionmentioning

confidence: 99%

A Hemodynamic Mechanism Correlating with the Initiation of MCA Bifurcation Aneurysms

Huang¹,

Zeng²,

Tao³

et al. 2020

AJNR Am J Neuroradiol

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BACKGROUND AND PURPOSE: Previous studies have reported that MCA bifurcation aneurysms usually emerge on inclined bifurcations; however, the reason is unclear. We designed this study to explore hemodynamic mechanisms that correlate with the initiation of MCA bifurcation aneurysms. MATERIALS AND METHODS: Fifty-four patients with unilateral MCA bifurcation aneurysms and 54 control patients were enrolled in this study after propensity score matching, and their clinical and CTA data were collected. We extracted the morphologic features of aneurysmal MCA bifurcations to build a simplified MCA bifurcation model and performed a computational fluid dynamics analysis. RESULTS: The presence of MCA aneurysms correlated with smaller parent-daughter angles of MCA bifurcations (P , .001). Aneurysmal MCA bifurcations usually presented with inclined shapes. The computational fluid dynamics analysis demonstrated that when arterial bifurcations became inclined, the high-pressure regions and low wall shear stress regions shifted from the apexes of the arterial bifurcations to the inclined daughter arteries, while the initial sites of MCA bifurcation aneurysms often overlapped with the shifted high-pressure regions and low wall shear stress regions. CONCLUSIONS: Our results suggest that the initiation of MCA bifurcation aneurysms may correlate with shifts of high-pressure regions and low wall shear stress regions that occur on inclined MCA bifurcations. ABBREVIATIONS: CFD ¼ computational fluid dynamics; HPR ¼ high-pressure region; LWSS ¼ low wall shear stress; LWSSR ¼ low wall shear stress region; PSM ¼ propensity score matching; RD ¼ ratio of diameter; ROC ¼ receiver operating characteristic T he occurrence of intracranial aneurysms is generally thought to be due to arterial wall weakening and/or the influence of hemodynamics. 1-4 Most studies on aneurysm etiology have focused on hemodynamics. Because the geometric shapes of intracranial arteries are diverse, their hemodynamics are also complex. Arterial bifurcations are common sites for intracranial aneurysms. The bifurcations are generally exposed to extreme hemodynamic stress; those with special morphologic features that significantly divert blood flow from the direction of flow of the parent vessels are a risk factor for aneurysm formation. 1,5,6 Previous studies have reported that the inclined MCA bifurcations with a widening angle are likely to harbor aneurysms, 7,8 but mechanisms by which the aneurysms develop on MCA bifurcations are controversial and need to be elucidated. 8-11 The present study was designed to extract the morphologic features of aneurysmal MCA bifurcations from clinical data, build a simplified MCA bifurcation model based on these extracted features, perform computational fluid dynamics (CFD) analysis on the aneurysmal MCA bifurcations and simplified models, and finally, to explore the hemodynamic mechanisms that could trigger aneurysm initiation. MATERIALS AND METHODS Case Selection and Matching Patients with unilateral MCA bifurcation aneurysms confirmed ...

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“…Furthermore, regions of low wall shear stress (WSS) have been related to wall enhancement. 19 Because low WSS is related to lower velocities near the wall, insufficient suppression of slow flow in VWI could have contributed to wall enhancement. Putting it into perspective, slow flow contributes to low WSS, which has been suggested to be related to inflammation in the aneurysm wall.…”

Section: Traditional Risk Factors (Lesion Size and Shape) Are Sensitimentioning

confidence: 99%

Insufficient slow-flow suppression mimicking aneurysm wall enhancement in magnetic resonance vessel wall imaging: a phantom study

Cornelissen

Leemans

Coolen

et al. 2019

Neurosurgical Focus

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OBJECTIVEMR vessel wall imaging (VWI) is increasingly performed in clinical settings to support treatment decision-making regarding intracranial aneurysms. Aneurysm wall enhancement after contrast agent injection is expected to be related to aneurysm instability and rupture status. However, the authors hypothesize that slow-flow artifacts mimic aneurysm wall enhancement. Therefore, in this phantom study they assess the effect of slow flow on wall-like enhancement by using different MR VWI techniques.METHODSThe authors developed an MR-compatible aneurysm phantom model, which was connected to a pump to enable pulsatile inflow conditions. For VWI, 3D turbo spin echo sequences—both with and without motion-sensitized driven equilibrium (MSDE) and delay alternating with nutation for tailored excitation (DANTE) preparation pulses—were performed using a 3-T MR scanner. VWI was acquired both before and after Gd contrast agent administration by using two different pulsatile inflow conditions (2.5 ml/sec peak flow at 77 and 48 beats per minute). The intraluminal signal intensity along the aneurysm wall was analyzed to assess the performance of slow-flow suppression.RESULTSThe authors observed wall-like enhancement after contrast agent injection, especially in low pump rate settings. Preparation pulses, in particular the DANTE technique, improved the performance of slow-flow suppression.CONCLUSIONSNear-wall slow flow mimics wall enhancement in VWI protocols. Therefore, VWI should be carefully interpreted. Preparation pulses improve slow-flow suppression, and therefore the authors encourage further development and clinical implementation of these techniques.

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Low Wall Shear Stress Is Associated with Local Aneurysm Wall Enhancement on High-Resolution MR Vessel Wall Imaging

Cited by 35 publications

References 23 publications

Multimodal validation of focal enhancement in intracranial aneurysms as a surrogate marker for aneurysm instability

Multimodal validation of focal enhancement in intracranial aneurysms as a surrogate marker for aneurysm instability

A Hemodynamic Mechanism Correlating with the Initiation of MCA Bifurcation Aneurysms

Insufficient slow-flow suppression mimicking aneurysm wall enhancement in magnetic resonance vessel wall imaging: a phantom study

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