Investigation on a Relationship Between Hemodynamics and Wall-Thinning in an Unruptured Human Cerebral Aneurysm

2012 ◽  
Author(s):  
Yasutaka Tobe ◽  
Takanobu Yagi ◽  
Sara Takahashi ◽  
Yuki Iwabuchi ◽  
Momoko Yamanashi ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Aneurysm ◽  
Medical Images ◽  
Cerebral Aneurysms ◽  
Flow Simulation ◽  
Patient Specific ◽  
Thin Walled Structures ◽  
Aneurysm Wall ◽  
Thin Walled ◽  
The Relationship

Recent studies of cerebral aneurysms are held using the blood flow simulation with patient-specific luminal geometries. In the study of development of cerebral aneurysms, wall shear stress (WSS) is focused as one of the key factors1–2. But the answer to the relationship between the extension of aneurysm and the theory of low WSS and high WSS still remains a question. One reason this question remains unsolved is because the current research about the cerebral aneurysms are held only using the vascular geometry developed from the medical images. From the intra-operative observation of cerebral aneurysms, the appearance of the cerebral aneurysm is not unified. Certain parts of the cerebral aneurysm have thin-walled structures where the blood flow of the aneurysm can be observed through the aneurysm wall. These differences in the wall structures cannot be predicted from the medical images. The purpose of this study is to see the relationship between hemodynamic patterns and thin-walled structure in human cerebral aneurysms.

A Theoretical Model for Saccular Cerebral Aneurysm Growth: Deformation and Stress Analysis

2007 ◽  
Author(s):  
Martin Kroon ◽  
Gerhard Holzapfel
Keyword(s):  
Cerebral Aneurysm ◽  
Cerebral Aneurysms ◽  
Structural Features ◽  
Constitutive Behavior ◽  
Patient Specific ◽  
Western World ◽  
Specific Information ◽  
Aneurysm Wall ◽  
Aneurysm Growth ◽  
Size Criterion

Aneurysms are abnormal dilatations of arteries, and these lesions are found almost exclusively in humans. Saccular cerebral aneurysms occur most frequently in the Circle of Willis, which is a circuit of arteries supplying the brain with blood. Aneurysms of this kind appear in a few percent of the human population in the Western world. Only a few percent of these lesions do actually rupture, but once rupture occurs the consequences are severe, often with death as outcome. Once a cerebral aneurysm is detected, clinicians need to decide whether operation is required or not. These decisions are mainly based on the size of the aneurysm, where larger aneurysms are considered to be more critical than smaller ones. This size criterion is, however, not very reliable, and criteria based on mechanical fields (stress or strain) of the aneurysm should be taken into account in the decision. This, however, requires knowledge of the constitutive behavior of the aneurysm wall, together with patient-specific information regarding geometry and boundary conditions. In order to be able to model the constitutive behavior of an aneurysm, the structural features of the aneurysm wall need to be determined. Knowledge of the etiology of the aneurysm may here provide important insights.

CFD Challenge: Solutions Using the Commercial Solver Fluent and the Open-Source Solver OpenFOAM

2012 ◽  
Author(s):  
P. Berg ◽  
G. Janiga ◽  
D. Thévenin
Keyword(s):  
Blood Flow ◽  
Cerebral Aneurysms ◽  
Flow Simulation ◽  
Patient Specific ◽  
Post Processing ◽  
Close Collaboration ◽  
Blood Flow Simulation ◽  
Unsteady Blood Flow ◽  
Commercial Solver ◽  
Considerable Experience

During the last decade, the research group in Magdeburg investigated the hemodynamics in cerebral aneurysms in close collaboration with experts from the fields of visualization and neuroradiology. Thanks to this, a considerable experience has been collected concerning unsteady blood flow simulation and analyses, involving a steadily increasing number of patient-specific aneurysms. Intermediate results have been presented at several VISC challenges. The simulations regarding this CFD Challenge as well as the post-processing have been carried out by the doctoral student Philipp Berg.

Classification of Blood Flow in Cerebral Aneurysm Considering the Parent Artery Curves

2013 ◽  
Author(s):  
Toshio Nakayama ◽  
Shin-ichiro Sugiyama ◽  
Makoto Ohta
Keyword(s):  
Blood Flow ◽  
Flow Pattern ◽  
Cerebral Aneurysm ◽  
Cerebral Aneurysms ◽  
Flow Simulation ◽  
Flow Speed ◽  
Parent Artery ◽  
Blood Flow Pattern ◽  
Stent Strut

Background and purpose: Recently, the number of endovascular treatments has increased worldwide because of advances in minimally invasive surgery. We considered the effect of reduced flow due to stent implantation and proposed the design of stent strut pattern from the viewpoint of fluid dynamics. We developed an optimized stent strut pattern using a computational fluid dynamics (CFD) system. A classification of cerebral aneurysms was proposed using the aspect ratio (AR) and the stent strut pattern was optimized. The results of optimal stent strut pattern for reduced blood flow speed and wall shear stress were different, and the influence of the AR values was small because there was no dependence on relationship between blood flow and the AR values due to the use of a straight pipe in the parent artery. The classification of blood flow pattern in a cerebral aneurysm must consider the parent artery curves. In this study, we investigated the relationship between the blood flow pattern in cerebral aneurysms and parent artery curves using CFD. Methods: To investigate the influence of blood flow based on the parent artery curve, the parent artery shape was constructed as follows. Patient-specific parent artery shape with a cerebral aneurysm was reconstructed using OsiriX. Center line was extracted using a vascular modeling tool kit. The parent artery shape was reconstructed based on this center line using CAD. The diameter of the parent artery was 4 mm. The cerebral aneurysm shape was a combination of a straight pipe and a half sphere, and the AR value was fixed at 1.0. The cerebral aneurysm position varied from the original position to a 180° rotated position. Tetrahedral numerical mesh was generated with a commercial mesh generator (ICEM CFD 14.0; Ansys Inc.) for the CFD analysis. The numerical blood flow simulation was performed on a supercomputer using the commercial ANSYS FLUENT 6.3 software package and the finite volume method, and a steady flow simulation was performed. Boundary conditions were set for velocity at the inlet, pressure at the outlet, no-slip parent artery, and stent surface. Reynolds numbers at the inlet determined from the mean blood flow speed were 240 and 600. Results and discussion: In this study, we revealed the blood flow pattern in some cerebral aneurysms using CFD. The pattern in a cerebral aneurysm was influenced by the aneurysm direction and parent artery curves. The blood flow pattern in a neck cerebral aneurysm was classified into two types.

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 Computed Tomography Image under Optimized Iterative Reconstruction Algorithm to Analyze the Characteristics of Blood Flow Field in Cerebral Aneurysm before and after Stent Implantation

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Kunyang Bao ◽  
Chao Liu ◽  
Jin Li ◽  
Xiang Liu ◽  
Wenzhang Luo ◽  
...  
Keyword(s):  
Blood Flow ◽  
Flow Field ◽  
Cerebral Aneurysm ◽  
Iterative Reconstruction ◽  
Stent Implantation ◽  
Cerebral Aneurysms ◽  
Reconstruction Algorithm ◽  
Ct Images ◽  
Iterative Reconstruction Algorithm ◽  
The Difference

In order to analyze the change characteristics of blood flow field in cerebral aneurysms before and after stent implantation, this study first constructed an optimized iterative reconstruction algorithm to reconstruct CT images of patients with cerebral aneurysms and used it to solve the problem of image sharpness. In addition, backprojection image reconstruction algorithm and Fourier transform analytic method were introduced. According to the CT images of cerebral arteries of patients, the lesions were presented in a three-dimensional and visual way through the reconstructed three-dimensional images, thus achieving the effects of simulation and simulation. The results showed that the sensitivity, specificity, and accuracy of the optimized iterative reconstruction algorithm were 90.78%, 83.27%, and 94.82%, which were significantly higher than those of the backprojection image reconstruction algorithm and Fourier transform analysis method, and the difference was statistically significant ( P < 0.05 ). Before operation, the blood flow velocity in the neck of aneurysm was 7.35 × 10−2 m/s, the exit velocity was 1.51 × 10−1 m/s, and the maximum velocity appeared in the upstream part of the exit. After passing through the aneurysm, the blood flow velocity began to decrease gradually, forming a vortex at the top of the tumor. After stent implantation, the neck and outlet velocities of cerebral aneurysm were 9.352 × 10−2 m/s and 1.897 × 10−2 m/s, respectively. The velocity of blood flow decreased after entering the aneurysm, and there was no vortex at the top of the aneurysm. Among the outlet velocities of arterial blood vessels, the velocity before stent implantation was significantly lower than that after stent implantation, and the difference was statistically significant ( P < 0.05 ). Compared with prestent, the shear force distribution on the wall of cerebral aneurysm showed a significant decrease, and the difference was statistically significant ( P < 0.05 ). To sum up, pelvic floor ultrasound based on hybrid iterative reconstruction algorithm has high accuracy in diagnosing the changes of blood flow field in cerebral aneurysms. The application of CT images in the diagnosis of cerebral aneurysms can objectively provide imaging data for clinical practice and has high application value.

Modeling the Geometry, Hemodynamics and Tissue Mechanics of Cerebral Aneurysms

2004 ◽  
Author(s):  
Baoshun Ma ◽  
Robert Harbaugh ◽  
Jia Lu ◽  
Madhavan Raghavan
Keyword(s):  
Shear Stress ◽  
Mechanical Stress ◽  
Cerebral Aneurysm ◽  
Residence Time ◽  
Cerebral Aneurysms ◽  
Lesion Size ◽  
Tissue Mechanics ◽  
Particle Residence Time ◽  
Aneurysm Wall ◽  
Geometric Size

The relationship between cerebral aneurysm geometry and biomechanics was investigated. Human cerebral aneurysm geometry was reconstructed from computed tomography angiography (CTA) and refined. Various indices of global geometric (size and shape) features were computed based on differential and computational geometry techniques. Computational fluid dynamics (CFD) simulations were performed to model both steady and pulsatile blood flow in the aneurysm and surrounding vasculature. Hemodynamic indices such as wall shear stress, pressure and particle residence time were obtained. Nonlinear finite element method (FEM) and a reported finite strain constitutive model were employed to estimate the distribution of mechanical stress in the aneurysm wall under static pressure. Shear stress, sac pressure and mechanical stress correlated better with lesion shape while particle residence time correlated better with lesion size.

Evaluation of Cerebral Aneurysm Stent Performance in a Subject-Specific Computational Model

2010 ◽  
Author(s):  
Timothy J. Gundert ◽  
John F. LaDisa
Keyword(s):  
United States ◽  
Blood Flow ◽  
Computational Model ◽  
Cerebral Aneurysm ◽  
Cerebral Aneurysms ◽  
The United States ◽  
Flow Stagnation ◽  
Subject Specific ◽  
Endovascular Devices ◽  
Saccular Aneurysms

Rupture of cerebral aneurysms is the second leading cause of stroke in the United States [1]. Altered hemodynamics is thought to play a role in the progression and subsequent rupture of aneurysms. Blood flow into an aneurysm can be occluded by surgically clipping the aneurysm or using endovascular devices, such as stents or coils. In saccular aneurysms, coiling alone may be a sufficient method of inducing flow stagnation in the aneurysm, causing thrombosis and preventing rupture. When treating wide-necked aneurysms, stenting is often used in conjunction with coiling to prevent the migration of coils. Many investigators have studied the ability of a stent-only treatment to favorably alter flow in aneurysms [2, 3].

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