scholarly journals Vortex Analysis of Intra-Aneurismal Flow in Cerebral Aneurysms

2016 ◽  
Vol 2016 ◽  
pp. 1-16 ◽  
Author(s):  
Kevin Sunderland ◽  
Christopher Haferman ◽  
Gouthami Chintalapani ◽  
Jingfeng Jiang
Keyword(s):  
Vortex Core ◽  
Cardiac Cycle ◽  
Temporal Stability ◽  
Cerebral Aneurysms ◽  
Patient Specific ◽  
Cfd Simulations ◽  
Hemodynamic Characteristics ◽  
Computational Fluid Dynamics Cfd ◽  
Marching Cube Algorithm ◽  
Core Characteristics

This study aims to develop an alternative vortex analysis method by measuring structure ofIntracranial aneurysm (IA) flow vortexes across the cardiac cycle, to quantify temporal stability of aneurismal flow. Hemodynamics were modeled in “patient-specific” geometries, using computational fluid dynamics (CFD) simulations. Modified versions of knownλ2andQ-criterion methods identified vortex regions; then regions were segmented out using the classical marching cube algorithm. Temporal stability was measured by the degree of vortex overlap (DVO) at each step of a cardiac cycle against a cycle-averaged vortex and by the change in number of cores over the cycle. No statistical differences exist in DVO or number of vortex cores between 5 terminal IAs and 5 sidewall IAs. No strong correlation exists between vortex core characteristics and geometric or hemodynamic characteristics of IAs. Statistical independence suggests this proposed method may provide novel IA information. However, threshold values used to determine the vortex core regions and resolution of velocity data influenced analysis outcomes and have to be addressed in future studies. In conclusions, preliminary results show that the proposed methodology may help give novel insight toward aneurismal flow characteristic and help in future risk assessment given more developments.

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.

Experimental and Numerical Flow Visualization in Patient Specific Pre Operative Human Airway Geometry

2011 ◽  
Author(s):  
Mathias Vermeulen ◽  
Cedric Van Holsbeke ◽  
Tom Claessens ◽  
Jan De Backer ◽  
Peter Van Ransbeeck ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Particle Image ◽  
Patient Specific ◽  
Lung Volume Reduction ◽  
Cfd Simulations ◽  
Piv Measurements ◽  
Image Velocimetry ◽  
Specific Geometry ◽  
Computational Fluid Dynamics Cfd ◽  
Human Airways

An experimental and numerical platform was developed to investigate the fluidodynamics in human airways. A pre operative patient specific geometry was used to create an identical experimental and numerical model. The experimental results obtained from Particle Image Velocimetry (PIV) measurements were compared to Computational Fluid Dynamics (CFD) simulations under stationary and pulsatile flow regimes. Together these results constitute the first step in predicting the clinical outcome of patients after lung surgeries such as Lung Volume Reduction.

scholarly journals A Workflow for Patient-Individualized Virtual Angiogram Generation Based on CFD Simulation

2012 ◽  
Vol 2012 ◽  
pp. 1-24 ◽  
Author(s):  
Jürgen Endres ◽  
Markus Kowarschik ◽  
Thomas Redel ◽  
Puneet Sharma ◽  
Viorel Mihalef ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Blood Flow ◽  
Shear Stress ◽  
Cfd Simulation ◽  
Cerebral Aneurysms ◽  
Patient Specific ◽  
Hemodynamic Parameters ◽  
Risk Of Rupture ◽  
Computational Fluid Dynamics Cfd ◽  
Subsequent Comparison

Increasing interest is drawn on hemodynamic parameters for classifying the risk of rupture as well as treatment planning of cerebral aneurysms. A proposed method to obtain quantities such as wall shear stress, pressure, and blood flow velocity is to numerically simulate the blood flow using computational fluid dynamics (CFD) methods. For the validation of those calculated quantities, virtually generated angiograms, based on the CFD results, are increasingly used for a subsequent comparison with real, acquired angiograms. For the generation of virtual angiograms, several patient-specific parameters have to be incorporated to obtain virtual angiograms which match the acquired angiograms as best as possible. For this purpose, a workflow is presented and demonstrated involving multiple phantom and patient cases.

scholarly journals CFD Simulations of Radioembolization: A Proof-of-Concept Study on the Impact of the Hepatic Artery Tree Truncation

Mathematics ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 839
Author(s):  
Unai Lertxundi ◽  
Jorge Aramburu ◽  
Julio Ortega ◽  
Macarena Rodríguez-Fraile ◽  
Bruno Sangro ◽  
...  
Keyword(s):  
Hepatic Artery ◽  
Liver Parenchyma ◽  
Patient Specific ◽  
Proof Of Concept ◽  
Cfd Simulations ◽  
Intraarterial Infusion ◽  
Computational Fluid Dynamics Cfd ◽  
The Impact ◽  
Healthy Liver ◽  
Simulation Time

Radioembolization (RE) is a treatment for patients with liver cancer, one of the leading cause of cancer-related deaths worldwide. RE consists of the transcatheter intraarterial infusion of radioactive microspheres, which are injected at the hepatic artery level and are transported in the bloodstream, aiming to target tumors and spare healthy liver parenchyma. In paving the way towards a computer platform that allows for a treatment planning based on computational fluid dynamics (CFD) simulations, the current simulation (model preprocess, model solving, model postprocess) times (of the order of days) make the CFD-based assessment non-viable. One of the approaches to reduce the simulation time includes the reduction in size of the simulated truncated hepatic artery. In this study, we analyze for three patient-specific hepatic arteries the impact of reducing the geometry of the hepatic artery on the simulation time. Results show that geometries can be efficiently shortened without impacting greatly on the microsphere distribution.

scholarly journals Multi-Scale, Patient-Specific Computational Flow Dynamics Models Predict Formation of Neointimal Hyperplasia in Saphenous Vein Grafts

2019 ◽  
Author(s):  
Francesca Donadoni ◽  
Cesar Pichardo-Almarza ◽  
Shervanthi Homer-Vanniasinkam ◽  
Alan Dardik ◽  
Vanessa Díaz-Zuccarini
Keyword(s):  
Neointimal Hyperplasia ◽  
Flow Dynamics ◽  
Patient Specific ◽  
Growth Mechanisms ◽  
Cfd Simulations ◽  
Vein Grafts ◽  
Multi Scale ◽  
Computational Flow Dynamics ◽  
Computational Fluid Dynamics Cfd ◽  
Dynamics Models

AbstractBypass occlusion due to neointimal hyperplasia (NIH) is among the major causes of peripheral graft failure. Its link to abnormal hemodynamics in the graft is complex, and isolated use of hemodynamic markers insufficient to fully capture its progression. Here, a computational model of NIH growth is presented, establishing a link between computational fluid dynamics (CFD) simulations of flow in the lumen, with a biochemical model representing NIH growth mechanisms inside the vessel wall. For all 3 patients analyzed, NIH at proximal and distal anastomoses was simulated by the model, with values of stenosis comparable to the computed tomography (CT) scans.

scholarly journals Computational Fluid Dynamics for Cerebral Aneurysms in Clinical Settings

2021 ◽  
pp. 27-32
Author(s):  
Fujimaro Ishida ◽  
Masanori Tsuji ◽  
Satoru Tanioka ◽  
Katsuhiro Tanaka ◽  
Shinichi Yoshimura ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Cerebral Aneurysms ◽  
Patient Specific ◽  
Clinical Settings ◽  
Geometry Model ◽  
Aneurysm Wall ◽  
3D Ct Angiography ◽  
Specific Geometry ◽  
Computational Fluid Dynamics Cfd

AbstractHemodynamics is thought to play an important role in the pathogenesis of cerebral aneurysms and recent development of computer technology makes it possible to simulate blood flow using high-resolution 3D images within several hours. A lot of studies of computational fluid dynamics (CFD) for cerebral aneurysms were reported; therefore, application of CFD for cerebral aneurysms in clinical settings is reviewed in this article.CFD for cerebral aneurysms using a patient-specific geometry model was first reported in 2003 and it has been revealing that hemodynamics brings a certain contribution to understanding aneurysm pathology, including initiation, growth and rupture. Based on the knowledge of the state-of-the-art techniques, this review treats the decision-making process for using CFD in several clinical settings. We introduce our CFD procedure using digital imaging and communication in medicine (DICOM) datasets of 3D CT angiography or 3D rotational angiography. In addition, we review rupture status, hyperplastic remodeling of aneurysm wall, and recurrence of coiled aneurysms using the hemodynamic parameters such as wall shear stress (WSS), oscillatory shear index (OSI), aneurysmal inflow rate coefficient (AIRC), and residual flow volume (RFV).

Abstract 1122‐000014: Effects of Patient‐Specific Blood Properties and Inflow Conditions on Hemodynamics in Cerebral Aneurysms

2021 ◽  
Vol 1 (S1) ◽  
Author(s):  
Yuya Uchiyama ◽  
Hiroyuki Takao ◽  
Soichiro Fujimura ◽  
Takashi Suzuki ◽  
Yuma Yamanaka ◽  
...  
Keyword(s):  
Cfd Simulation ◽  
Cerebral Aneurysms ◽  
Patient Specific ◽  
Parent Artery ◽  
Computational Domain ◽  
Cfd Simulations ◽  
Mean Velocity ◽  
Visual Evaluation ◽  
The Mean ◽  
Inflow Conditions

Introduction : Computational Fluid Dynamics (CFD) simulation is an effective tool to investigate pathologies and clinical outcomes of cerebral aneurysms from the hemodynamic perspective. However, simulation conditions such as the blood properties and boundary conditions are usually referred to in the literature do not consider patient‐specific values. In this study, we measured blood properties and extracted the inflow conditions from four‐dimensional digital subtraction angiography (4D‐DSA) images for patients who underwent flow diverter (FD) deployment. Then, we conducted CFD simulations considering the deployed FD geometry to investigate the effect of patient‐specific conditions on aneurysmal hemodynamics. Methods : We took whole blood samples of five patients with intracranial aneurysms just before the surgery and measured the blood density and viscosity with a densitometer and a falling needle rheometer. The patients underwent 4D‐DSA imaging, from which we calculated the patient‐specific inflow velocity of each patient using an in‐house flow extraction program. We used in‐house virtual FD deployment software to reproduce the FD geometry for each patient. We then defined the computational domain including the FD geometry. Four CFD simulations were performed for each of the five patients: (1) a steady CFD simulation under a referred Newtonian blood model and previously published inflow conditions as a basic simulation pattern (2) a CFD simulation including the patient‐specific non‐Newtonian blood properties only, (3) a CFD simulation including the inflow conditions only, and (4) a CFD simulation including both the patient‐specific blood properties and inflow conditions. We calculated the mean velocity in the aneurysm normalized by the mean velocity in the parent artery and the wall shear stress (WSS) of the aneurysm. We compared the results of the four CFD simulations and calculated their differences based on the values for the basic simulation pattern. Results : Based on the visual evaluation, the flow structures of the four CFD simulation patterns differed only slightly from each other, but a quantitative comparison revealed that there were large differences in the hemodynamic parameters. For the velocity, there was an average 14.2% difference with the steady CFD simulation results when the patient‐specific blood properties are considered, and an average 35.8% difference when the patient‐specific inflow conditions are considered. There was an average 60.7% difference when both the patient‐specific blood properties and inflow conditions are taken into account. For the WSS, there was an average 8.75% difference when including the patient‐specific blood properties and an average 66.8% difference in including the patient‐specific inflow conditions. There was an average 69.3% difference in including both conditions are considered. It appeared that the effect of including patient‐specific inflow conditions was more substantial than that of including the patient‐specific blood properties, and most robust when both conditions were included. Conclusions : The hemodynamics obtained from CFD simulations with the deployed FD appears to strongly depend on both the blood properties and the inflow conditions. This result implies that CFD simulations with the referred conditions may not accurately reproduce the hemodynamics. It was confirmed that patient‐specific conditions should be included in CFD simulations.

PIV-Measured Versus CFD-Predicted Flow Dynamics in Anatomically Realistic Cerebral Aneurysm Models

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Matthew D. Ford ◽  
Hristo N. Nikolov ◽  
Jaques S. Milner ◽  
Stephen P. Lownie ◽  
Edwin M. DeMont ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
Cardiac Cycle ◽  
Flow Dynamics ◽  
Cfd Modeling ◽  
Patient Specific ◽  
Flow Loop ◽  
Cfd Simulations ◽  
Flow Through

Computational fluid dynamics (CFD) modeling of nominally patient-specific cerebral aneurysms is increasingly being used as a research tool to further understand the development, prognosis, and treatment of brain aneurysms. We have previously developed virtual angiography to indirectly validate CFD-predicted gross flow dynamics against the routinely acquired digital subtraction angiograms. Toward a more direct validation, here we compare detailed, CFD-predicted velocity fields against those measured using particle imaging velocimetry (PIV). Two anatomically realistic flow-through phantoms, one a giant internal carotid artery (ICA) aneurysm and the other a basilar artery (BA) tip aneurysm, were constructed of a clear silicone elastomer. The phantoms were placed within a computer-controlled flow loop, programed with representative flow rate waveforms. PIV images were collected on several anterior-posterior (AP) and lateral (LAT) planes. CFD simulations were then carried out using a well-validated, in-house solver, based on micro-CT reconstructions of the geometries of the flow-through phantoms and inlet/outlet boundary conditions derived from flow rates measured during the PIV experiments. PIV and CFD results from the central AP plane of the ICA aneurysm showed a large stable vortex throughout the cardiac cycle. Complex vortex dynamics, captured by PIV and CFD, persisted throughout the cardiac cycle on the central LAT plane. Velocity vector fields showed good overall agreement. For the BA, aneurysm agreement was more compelling, with both PIV and CFD similarly resolving the dynamics of counter-rotating vortices on both AP and LAT planes. Despite the imposition of periodic flow boundary conditions for the CFD simulations, cycle-to-cycle fluctuations were evident in the BA aneurysm simulations, which agreed well, in terms of both amplitudes and spatial distributions, with cycle-to-cycle fluctuations measured by PIV in the same geometry. The overall good agreement between PIV and CFD suggests that CFD can reliably predict the details of the intra-aneurysmal flow dynamics observed in anatomically realistic in vitro models. Nevertheless, given the various modeling assumptions, this does not prove that they are mimicking the actual in vivo hemodynamics, and so validations against in vivo data are encouraged whenever possible.

scholarly journals Validation of CFD Simulations of Cerebral Aneurysms With Implication of Geometric Variations

2006 ◽  
Vol 128 (6) ◽  
pp. 844-851 ◽  
Author(s):  
Yiemeng Hoi ◽  
Scott H. Woodward ◽  
Minsuok Kim ◽  
Dale B. Taulbee ◽  
Hui Meng
Keyword(s):  
Flow Field ◽  
Cfd Simulation ◽  
Three Dimensional ◽  
Cerebral Aneurysms ◽  
Patient Specific ◽  
Hemodynamic Parameters ◽  
Cfd Simulations ◽  
Piv Measurements ◽  
Cfd Method ◽  
Aneurysm Model

Background. Computational fluid dynamics (CFD) simulations using medical-image-based anatomical vascular geometry are now gaining clinical relevance. This study aimed at validating the CFD methodology for studying cerebral aneurysms by using particle image velocimetry (PIV) measurements, with a focus on the effects of small geometric variations in aneurysm models on the flow dynamics obtained with CFD. Method of Approach. An experimental phantom was fabricated out of silicone elastomer to best mimic a spherical aneurysm model. PIV measurements were obtained from the phantom and compared with the CFD results from an ideal spherical aneurysm model (S1). These measurements were also compared with CFD results, based on the geometry reconstructed from three-dimensional images of the experimental phantom. We further performed CFD analysis on two geometric variations, S2 and S3, of the phantom to investigate the effects of small geometric variations on the aneurysmal flow field. Results. We found poor agreement between the CFD results from the ideal spherical aneurysm model and the PIV measurements from the phantom, including inconsistent secondary flow patterns. The CFD results based on the actual phantom geometry, however, matched well with the PIV measurements. CFD of models S2 and S3 produced qualitatively similar flow fields to that of the phantom but quantitatively significant changes in key hemodynamic parameters such as vorticity, positive circulation, and wall shear stress. Conclusion. CFD simulation results can closely match experimental measurements as long as both are performed on the same model geometry. Small geometric variations on the aneurysm model can significantly alter the flow-field and key hemodynamic parameters. Since medical images are subjected to geometric uncertainties, image-based patient-specific CFD results must be carefully scrutinized before providing clinical feedback.

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