Direct numerical simulation of transitional flow in a patient-specific intracranial aneurysm

Valen‐Sendstad, Kristian; Mardal, Kent‐André; Mortensen, Mikael; Reif, Bjørn Anders Pettersson; Langtangen, Hans Petter

doi:10.1016/j.jbiomech.2011.08.015

Cited by 118 publications

(69 citation statements)

References 41 publications

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“…Indeed, there is now independent evidence for such flow instabilities based on high-resolution particle image velocimetry of realistic flow in a compliant model of a patient-specific aneurysm, which revealed transitional flow phenomena during the deceleration phase, 29 consistent with data presented in the current study. Hence, as has previously been argued on the basis of HR CFD findings 17,18 and as the authors of the particle image velocimetry study also emphasized, 29 though there is a widely held conception that aneurysm flow is laminar (ie, stable, or with periodic instabilities and/or vortex shedding; as opposed to turbulent flows or laminar/transitional flows, with high-frequency, non-periodic instabilities having small spatial and temporal scales), evidence suggests that this a priori assumption, which is often used implicitly or explicitly to rationalize NR solution strategies, must be reconsidered.…”

Section: Discussionsupporting

confidence: 59%

“…[11][12][13] To illustrate the potential gap between what may be termed normal-resolution (NR) and high-resolution (HR) solution strategies, consider that the broadest CFD-based studies of aneurysm rupture status have reported using 100 time-steps per cardiac cycle with meshes of 1 to 5 million tetrahedra 14 or 1000 time-steps per cycle with 300,000 to 1 million elements. 2 On the other hand, recent case studies using tens of thousands of time-steps per cardiac cycle and tens of millions of tetrahedral elements (or the equivalent) have reported the presence of highly unstable and possibly turbulent flows, [15][16][17][18] consistent with clinical observations 19 but seemingly at odds with most published aneurysm CFD studies. The impact of the solution strategy was also evident in a recent CFD Challenge, 20 which highlighted, for the same aneurysm case, a wide variety of aneurysm inflow patterns contributed by 25 groups, most using a range of NR strategies.…”

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confidence: 64%

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Mind the Gap: Impact of Computational Fluid Dynamics Solution Strategy on Prediction of Intracranial Aneurysm Hemodynamics and Rupture Status Indicators

Valen‐Sendstad

Steinman

2013

AJNR Am J Neuroradiol

147

114

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BACKGROUND AND PURPOSE:Computational fluid dynamics has become a popular tool for studying intracranial aneurysm hemodynamics, demonstrating success for retrospectively discriminating rupture status; however, recent highly refined simulations suggest potential deficiencies in solution strategies normally used in the aneurysm computational fluid dynamics literature. The purpose of the present study was to determine the impact of this gap.

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Section: Discussionsupporting

confidence: 59%

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confidence: 64%

Mind the Gap: Impact of Computational Fluid Dynamics Solution Strategy on Prediction of Intracranial Aneurysm Hemodynamics and Rupture Status Indicators

Valen‐Sendstad

Steinman

2013

AJNR Am J Neuroradiol

147

114

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“…This definition is mathematically equivalent to turbulence kinetic energy, which was used previously [17,25]. (However, note that the fluctuations are not necessarily fully developed turbulence.)…”

Section: Quantification Of Flow Fluctuations and Classification Ofmentioning

confidence: 99%

Flow Instability Detected by High-Resolution Computational Fluid Dynamics in Fifty-Six Middle Cerebral Artery Aneurysms

Varble

Xiang

Lin

et al. 2016

Journal of Biomechanical Engineering

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Recent high-resolution computational fluid dynamics (CFD) studies have detected persistent flow instability in intracranial aneurysms (IAs) that was not observed in previous in silico studies. These flow fluctuations have shown incidental association with rupture in a small aneurysm dataset. The aims of this study are to explore the capabilities and limitations of a commercial CFD solver in capturing such velocity fluctuations, whether fluctuation kinetic energy (fKE) as a marker to quantify such instability could be a potential parameter to predict aneurysm rupture, and what geometric parameters might be associated with such fluctuations. First, we confirmed that the second-order discretization schemes and high spatial and temporal resolutions are required to capture these aneurysmal flow fluctuations. Next, we analyzed 56 patient-specific middle cerebral artery (MCA) aneurysms (12 ruptured) by transient, high-resolution CFD simulations with a cycle-averaged, constant inflow boundary condition. Finally, to explore the mechanism by which such flow instabilities might arise, we investigated correlations between fKE and several aneurysm geometrical parameters. Our results show that flow instabilities were present in 8 of 56 MCA aneurysms, all of which were unruptured bifurcation aneurysms. Statistical analysis revealed that fKE could not differentiate ruptured from unruptured aneurysms. Thus, our study does not lend support to these flow instabilities (based on a cycle-averaged constant inflow as opposed to peak velocity) being a marker for rupture. We found a positive correlation between fKE and aneurysm size as well as size ratio. This suggests that the intrinsic flow instability may be associated with the breakdown of an inflow jet penetrating the aneurysm space.

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“…They proposed that the oscillatory behavior of WSS vectors might play an important role in the formation of an aneurysm. Valen-Sendstad et al (2011) studied the effects of turbulence in a patient-specific middle cerebral aneurysm (MCA) using ultra-high resolution direct numerical simulations (DNS). High-frequency velocity fluctuations ranged between 1-500Hz were detected, which suggests that turbulence could be present in MCA aneurysms.…”

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confidence: 99%

Low-frequency harmonics in inlet flow rate play a crucial role in inducing flow instabilities in terminal cerebral aneurysms

Saito

Yokoyama

et al. 2016

JBSE

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Low-frequency harmonics in inlet flow rate play a crucial role in inducing flow instabilities in terminal cerebral aneurysms IntroductionHemodynamic factors play an important role in the initiation, growth and rupture of cerebral aneurysms. Understanding the mechanisms associated with these events could contribute to making a more accurate assessment of rupture risk, and therefore avoid unnecessary surgical operations. With computational fluid dynamics (CFD) modeling of aneurysm hemodynamics, several hemodynamic factors, such as wall shear stress (WSS), oscillatory shear index (OSI), impingement regions, inflow jet sizes, and pressure loss coefficient have been presented as key indicators for the rupture risk (Cebral et al., 2005;Dhar et al., 2008;Dolan et al., 2013;Sforza et al., 2009;Takao et al., 2012;Xiang et al., 2011). Xiang et al. (2011 analyzed 38 ruptured and 81 unruptured aneurysms using CFD-based models and proposed that low WSS and high OSI correlated with aneurysm rupture. On the contrary, Cebral et al. (2011) studied 210 aneurysms with CFD models and correlated the elevated levels of the maximum WSS with a clinical history of prior aneurysm rupture. In order to explain such inconsistent results and/or conclusions, Meng et al. (2014) proposed that both high and low WSS might cause the growth and rupture of cerebral aneurysms with independent pathways, but it is still unclear whether the complex rupture mechanism or different experiment designs (small sample size, inconsistent parameter definitions and model assumptions) lead to the controversy results.Recently, flow instability-related studies in vessels and aneurysms have been carried out experimentally and numerically for a better understanding of the rupture mechanisms. Flow fluctuations have been observed in aneurysms Lijian XU*, Atsushi SAITO**, Yoko YOKOYAMA***, Kenya SATO***, Tatsuya SASAKI**, Ryuhei YAMAGUCHI*, Michiko SUGAWARA*and Hao LIU* *Graduate School of Engineering, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba-shi, Chiba, Japan E-mail: hliu@faculty.chiba-u.jp ** Department of Neurosurgery, Aomori Prefectural Central Hospital, 2-1-1 Higashitsukurimichi, Aomori, Japan *** Department of Radiology, Aomori Prefectural Central Hospital, 2-1-1 Higashitsukurimichi, Aomori, Japan AbstractPrediction of rupture status in cerebral aneurysms remains challenging for clinicians, and the important rupture indicator (wall shear stress, WSS) is controversially discussed. Recent studies report that flow instabilities appear to play an influential role in the evolution and rupture of aneurysms and it is strongly correlated with both geometries and inlet flow rate waveforms. However, how frequency harmonics in inlet flow rate waveforms influence the flow instabilities and hence WSS fluctuations in cerebral aneurysms are still unclear.In this study, we used a computational fluid dynamic (CFD) model of anatomically realistic cerebral aneurysms combining with Fourier series and power spectral density (PSD) analysis to investigate the association betwee...

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Direct numerical simulation of transitional flow in a patient-specific intracranial aneurysm

Cited by 118 publications

References 41 publications

Mind the Gap: Impact of Computational Fluid Dynamics Solution Strategy on Prediction of Intracranial Aneurysm Hemodynamics and Rupture Status Indicators

Mind the Gap: Impact of Computational Fluid Dynamics Solution Strategy on Prediction of Intracranial Aneurysm Hemodynamics and Rupture Status Indicators

Flow Instability Detected by High-Resolution Computational Fluid Dynamics in Fifty-Six Middle Cerebral Artery Aneurysms

Low-frequency harmonics in inlet flow rate play a crucial role in inducing flow instabilities in terminal cerebral aneurysms

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