Numerical Simulation of Pre- and Postsurgical Flow in a Giant Basilar Aneurysm

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Vitaliy L. Rayz ◽  
Michael T. Lawton ◽  
Alastair J. Martin ◽  
William L. Young ◽  
David Saloner
Keyword(s):  
Numerical Simulation ◽  
Vertebral Artery ◽  
Computational Models ◽  
Numerical Solutions ◽  
Cerebral Aneurysms ◽  
Flow Region ◽  
Secondary Flows ◽  
Patient Specific ◽  
Interventional Treatment ◽  
Slow Flow

Computational modeling of the flow in cerebral aneurysms is an evolving technique that may play an important role in surgical planning. In this study, we simulated the flow in a giant basilar aneurysm before and after surgical takedown of one vertebral artery. Patient-specific geometry and flowrates obtained from magnetic resonance (MR) angiography and velocimetry were used to simulate the flow prior to and after the surgery. Numerical solutions for steady and pulsatile flows were obtained. Highly three-dimensional flows, with strong secondary flows, were computed in the aneurysm in the presurgical and postsurgical conditions. The computational results predicted that occlusion of a vertebral artery would result in a significant increase of the slow flow region formed in the bulge of the aneurysm, where increased particle residence time and velocities lower than 2.5cm∕s were computed. The region of slow flow was found to have filled with thrombus following surgery. Predictions of numerical simulation methods are consistent with the observed outcome following surgical treatment of an aneurysm. The study demonstrates that computational models may provide hypotheses to test in future studies, and might offer guidance for the interventional treatment of cerebral aneurysms.

Coupling the Haemodynamic Environment to the Evolution of Cerebral Aneurysms

2009 ◽  
Author(s):  
Paul N. Watton ◽  
Yiannis Ventikos ◽  
Gerhard A. Holzapfel
Keyword(s):  
Interventional Procedures ◽  
Computational Models ◽  
Cerebral Aneurysms ◽  
Mortality Rates ◽  
Patient Specific ◽  
High Morbidity ◽  
Future Evolution ◽  
Elective Repair ◽  
Risk Of Rupture ◽  
Very High

Cerebral aneurysms are thought to be present in 2–5% of the general population. Most aneurysms remain asymptomatic and of those that are detected, the risk of rupture is relatively low, i.e. 0.1–1% per year. However, very high morbidity and mortality rates are associated with an aneurysm that does rupture (30–50%). Consequently, elective repair of an aneurysm at high risk of rupture may be deemed appropriate. Unfortunately, interventional procedures are themselves not without risk and have morbidity rates of up to 6%. Moreover, it is difficult to quantify the risk of rupture on a patient specific basis: more sophisticated diagnostic criteria are required. Computational models of aneurysm evolution aim to improve the understanding of the aetiology of the disease. The ultimate aim is to predict future evolution and rupture.

scholarly journals Numerical Simulation of the Intra-Aneurysmal Flow Dynamics

2006 ◽  
Vol 12 (1_suppl) ◽  
pp. 49-52 ◽  
Author(s):  
M. Shojima ◽  
M. Oshima ◽  
K. Takagi ◽  
M. Hayakawa ◽  
K. Katada ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Three Dimensional ◽  
Cerebral Aneurysms ◽  
Computed Tomographic Angiography ◽  
Flow Dynamics ◽  
Patient Specific ◽  
Geometrical Parameters ◽  
Computed Tomographic ◽  
Tomographic Angiography ◽  
Middle Cerebral Artery Aneurysms

Intra-aneurysmal flow dynamics is analyzed qualitatively and quantitatively with numerical simulation technique, and presented for the future clinical application in embolizing cerebral aneurysms. From the volumetric data obtained by three-dimensional computed tomographic angiography, patient-specific vessel models were created for 16 middle cerebral artery aneurysms. Intra-aneurysmal flow dynamics was visualized and analyzed qualitatively, and the geometrical parameters of vessels and aneurysms that affect the intra-aneurysmal flow dynamics were determined quantitatively by correlation analysis. The flow velocity was delayed in the aneurysm cavity, especially at its tip where the rupture usually occurs. The intra-aneurysmal flow dynamics was considerably influenced by the geometrical parameters that are related to the width of the neck and the branching angle of larger branch artery. The intra-aneurysmal flow dynamics is complex, and the numerical flow simulations with patient-specific vascular models seems effective in understanding the flow dynamics and planning the endovascular treatment of cerebral aneurysms.

scholarly journals How patient specific are patient-specific computational models of cerebral aneurysms? An overview of sources of error and variability

2019 ◽  
Vol 47 (1) ◽  
pp. E14 ◽  
Author(s):  
David A. Steinman ◽  
Vitor M. Pereira
Keyword(s):  
Computational Models ◽  
Cerebral Aneurysms ◽  
Patient Specific ◽  
The Past ◽  
Sources Of Error ◽  
3D Angiography ◽  
Uncertain Model ◽  
Patient Specific Modeling ◽  
Specific Modeling ◽  
Different Sources

Computational modeling of cerebral aneurysms, derived from clinical 3D angiography, has become widespread over the past 15 years. While such “image-based” or “patient-specific” models have shown promise for the assessment of rupture risk, much debate remains about their reliability in light of necessary modeling assumptions and incomplete or uncertain model input parameters derived from the clinic. The aims of this review were to walk through the various steps of this so-called patient-specific modeling pipeline and to highlight evidence supporting those steps that we can or cannot rely on. The relative importance of the different sources of error and variability on hemodynamic predictions is summarized, with recommendations to standardize for those that can be avoided and to pay closer attention those to that cannot.

Numerical Modeling of the Flow in Cerebral Aneurysms Can Predict Thrombus Deposition Regions Following Vascular Interventions

2013 ◽  
Author(s):  
V. L. Rayz ◽  
G. Acevedo-Bolton ◽  
M. T. Lawton ◽  
V. Halbach ◽  
J. R. Leach ◽  
...  
Keyword(s):  
Treatment Options ◽  
Cerebral Aneurysms ◽  
Flow Diverter ◽  
Patient Specific ◽  
Interventional Treatment ◽  
Shear Stresses ◽  
Parent Vessel ◽  
Vessel Occlusion ◽  
Flow Diverter Stent ◽  
Proximal Occlusion

Giant intracranial aneurysms present a grave danger of hemorrhage, cerebral compression, and thromboembolism. Fusiform aneurysms present a particular challenge for interventional treatment since these lesions cannot be completely removed from the circulation by clipping or coiling without sacrificing flow to the distal vasculature. In some cases, these lesions can be treated by interventions eliminating pathological hemodynamics, such as indirect aneurysm occlusion or deployment of a flow diverter stent (FDS). The first approach consists of proximal occlusion, distal occlusion, or trapping, sometimes performed with a bypass supplying flow from collateral circulation. In the second approach, a flow diverter device is used to reconstruct the parent vessel geometry and redirect the flow away from the aneurysmal sac. This is achieved due to the denser struts of an FDS relative to a standard stent, which provide resistance to the flow across its walls. Both interventional approaches often result in thrombus deposition (TD) in the aneurysm sac that is considered protective. Despite their advantages, these treatments introduce complications related to thrombotic occlusion of vital perforators or branch arteries. A virtual model, that could predict TD regions that result from flow alteration could help evaluate various treatment options. In addition to biochemical factors, an important role in the TD process may be played by hemodynamics. Previous studies demonstrated that flow regions with elevated TD potential are characterized by low velocities and near-wall shear stresses as well as increased flow residence time [1, 2]. The current study extends this patient-specific CFD methodology to predict TD regions following vascular interventions, such as proximal vessel occlusion and FDS deployment.

scholarly journals Morphological and Hemodynamic Changes during Cerebral Aneurysm Growth

2021 ◽  
Vol 11 (4) ◽  
pp. 520
Author(s):  
Emily R. Nordahl ◽  
Susheil Uthamaraj ◽  
Kendall D. Dennis ◽  
Alena Sejkorová ◽  
Aleš Hejčl ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Kinetic Energy ◽  
Swirling Flow ◽  
Morphological Changes ◽  
Cerebral Aneurysms ◽  
Patient Specific ◽  
Aneurysm Wall ◽  
Aneurysm Growth ◽  
Computational Fluid Dynamics Cfd

Computational fluid dynamics (CFD) has grown as a tool to help understand the hemodynamic properties related to the rupture of cerebral aneurysms. Few of these studies deal specifically with aneurysm growth and most only use a single time instance within the aneurysm growth history. The present retrospective study investigated four patient-specific aneurysms, once at initial diagnosis and then at follow-up, to analyze hemodynamic and morphological changes. Aneurysm geometries were segmented via the medical image processing software Mimics. The geometries were meshed and a computational fluid dynamics (CFD) analysis was performed using ANSYS. Results showed that major geometry bulk growth occurred in areas of low wall shear stress (WSS). Wall shape remodeling near neck impingement regions occurred in areas with large gradients of WSS and oscillatory shear index. This study found that growth occurred in areas where low WSS was accompanied by high velocity gradients between the aneurysm wall and large swirling flow structures. A new finding was that all cases showed an increase in kinetic energy from the first time point to the second, and this change in kinetic energy seems correlated to the change in aneurysm volume.

scholarly journals Supervised Domain Adaptation for Automated Semantic Segmentation of the Atrial Cavity

Entropy ◽  
2021 ◽  
Vol 23 (7) ◽  
pp. 898
Author(s):  
Marta Saiz-Vivó ◽  
Adrián Colomer ◽  
Carles Fonfría ◽  
Luis Martí-Bonmatí ◽  
Valery Naranjo
Keyword(s):  
High Performance ◽  
Computational Models ◽  
Domain Adaptation ◽  
Semantic Segmentation ◽  
Patient Specific ◽  
Mr Images ◽  
Training Samples ◽  
Volumetric Images ◽  
Acquisition Costs ◽  
Left And Right

Atrial fibrillation (AF) is the most common cardiac arrhythmia. At present, cardiac ablation is the main treatment procedure for AF. To guide and plan this procedure, it is essential for clinicians to obtain patient-specific 3D geometrical models of the atria. For this, there is an interest in automatic image segmentation algorithms, such as deep learning (DL) methods, as opposed to manual segmentation, an error-prone and time-consuming method. However, to optimize DL algorithms, many annotated examples are required, increasing acquisition costs. The aim of this work is to develop automatic and high-performance computational models for left and right atrium (LA and RA) segmentation from a few labelled MRI volumetric images with a 3D Dual U-Net algorithm. For this, a supervised domain adaptation (SDA) method is introduced to infer knowledge from late gadolinium enhanced (LGE) MRI volumetric training samples (80 LA annotated samples) to a network trained with balanced steady-state free precession (bSSFP) MR images of limited number of annotations (19 RA and LA annotated samples). The resulting knowledge-transferred model SDA outperformed the same network trained from scratch in both RA (Dice equals 0.9160) and LA (Dice equals 0.8813) segmentation tasks.

scholarly journals Computational Modeling of Vortex Generators for Turbomachinery

2002 ◽  
Author(s):  
R. V. Chima
Keyword(s):  
Computational Models ◽  
Body Force ◽  
Secondary Flows ◽  
The Body ◽  
Vortex Generators ◽  
Force Model ◽  
Suction Surface ◽  
Near Surface ◽  
Compressor Rotor ◽  
Surface Particle

In this work computational models were developed and used to investigate applications of vortex generators (VGs) to turbomachinery. The work was aimed at increasing the efficiency of compressor components designed for the NASA Ultra Efficient Engine Technology (UEET) program. Initial calculations were used to investigate the physical behavior of VGs. A parametric study of the effects of VG height was done using 3-D calculations of isolated VGs. A body force model was developed to simulate the effects of VGs without requiring complicated grids. The model was calibrated using 2-D calculations of the VG vanes and was validated using the 3-D results. Then three applications of VGs to a compressor rotor and stator were investigated: 1. The results of the 3-D calculations were used to simulate the use of small casing VGs used to generate rotor preswirl or counterswirl. Computed performance maps were used to evaluate the effects of VGs. 2. The body force model was used to simulate large partspan splitters on the casing ahead of the stator. Computed loss buckets showed the effects of the VGs. 3. The body force model was also used to investigate the use of tiny VGs on the stator suction surface for controlling secondary flows. Near-surface particle traces and exit loss profiles were used to evaluate the effects of the VGs.

Numerical Simulation of Blood Flow in Patient-Specific Stenotic Carotid Bifurcation Geometries

2009 ◽  
Author(s):  
Megan Cummins ◽  
Jenn S. Rossmann
Keyword(s):  
Vortex Shedding ◽  
Carotid Bifurcation ◽  
Secondary Flows ◽  
Patient Specific ◽  
Mechanical Forces ◽  
Plaque Vulnerability ◽  
Governing Equations ◽  
Unstable Plaque ◽  
Recirculation Zones ◽  
Insight Into

The hemodynamics and fluid mechanical forces in blood vessels have long been implicated in the deposition and growth of atherosclerotic plaque. Detailed information about the hemodynamics in vessels affected by significant plaque deposits can provide insight into the mechanisms and likelihood of plaque weakening and rupture. In the current study, the governing equations are solved in their finite volume formulation in several patient-specific geometries. Recirculation zones, vortex shedding, and secondary flows are captured. The forces on vessel walls are shown to correlate with unstable plaque deposits. The results of these simulations suggest morphological features that may usefully supplement percent stenosis as a predictor of plaque vulnerability.

A Numerical and Experimental Investigation of Turbulent Heat Transport Downstream From an Abrupt Pipe Expansion

1983 ◽  
Vol 105 (4) ◽  
pp. 862-869 ◽  
Author(s):  
R. S. Amano ◽  
M. K. Jensen ◽  
P. Goel
Keyword(s):  
Heat Transfer ◽  
Numerical Solutions ◽  
Numerical Study ◽  
Separated Flow ◽  
Flow Region ◽  
Reynolds Numbers ◽  
Turbulent Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Pipe Expansion

An experimental and numerical study is reported on heat transfer in the separated flow region created by an abrupt circular pipe expansion. Heat transfer coefficients were measured along the pipe wall downstream from an expansion for three different expansion ratios of d/D = 0.195, 0.391, and 0.586 for Reynolds numbers ranging from 104 to 1.5 × 105. The results are compared with the numerical solutions obtained with the k ∼ ε turbulence model. In this computation a new finite difference scheme is developed which shows several advantages over the ordinary hybrid scheme. The study also covers the derivation of a new wall function model. Generally good agreement between the measured and the computed results is shown.

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