scholarly journals MRV-validated numerical flow analysis of thrombotic potential of coronary stent designs

2019 ◽  
Vol 5 (1) ◽  
pp. 77-80
Author(s):  
Jan Oldenburg ◽  
Finja Borowski ◽  
Klaus-Peter Schmitz ◽  
Michael Stiehm ◽  
Alper Ö Öner ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Cross Sections ◽  
Flow Analysis ◽  
Mechanical Analysis ◽  
Test Fluid ◽  
Stent Design ◽  
Flow Topology ◽  
Open Cell ◽  
Magnetic Resonance Velocimetry ◽  
Helical Stent

AbstractThe formation of a thrombus is associated with dramatic consequences for the patient, such as increased risks of neurologic events and myocardial infarction or even death. A pathologically altered blood flow is associated with these complications. Consequently, a consistent fluid-mechanical analysis of implants, such as coronary stents, must be carried out. Computational fluid dynamics (CFD) is an important in silico tool for the analysis of different stent designs. Using three different generic stent designs (closed-cell, open-cell and helical), CFD could be performed with the OpenFOAM software package. The stents were implemented in a vascular model having a fully developed Hagen-Poiseuille velocity profile (umean = 0.6 m/s) as inlet condition. In combination with the dynamic viscosity of the Newtonian test fluid of 6.04·10-5m2/s, Reynolds numbers up to 460 were achieved. Spatially high-resolved velocity fields from measurements in the magnetic resonance tomograph (magnetic resonance velocimetry, MRV) were available for validation. The velocity field was compared in selected cross sections and longitudinal sections. The difference of the main flow proximal and distal to the stent models were below 6 %. In addition, a similar flow topology could be quantified using the Q-criterion. Due to the very good agreement of the numerical results with the MRV-measurements, the numerical method has been applied to further analysis of stent designs regarding to time average wall shear stress (TAWSS) distribution on the luminal vessel surface (surface area with TAWSS < 0.4 Pa was related to overall vessel surface) under pulsatile conditions. Although all stent designs have the same square cross-section, a large influence of the stent design on WSS distribution could be observed (closedcell vs. helical = -50.2 %; open-cell vs. helical = -38.5 %). By using validated CFD it was possible to quantify the hemodynamic benefit of helical stent design in terms of thrombosis potential.

scholarly journals Measurement of cytoplasmic streaming in single plant cells by magnetic resonance velocimetry

2009 ◽  
Vol 642 ◽  
pp. 5-14 ◽  
Author(s):  
JAN-WILLEM VAN DE MEENT ◽  
ANDY J. SEDERMAN ◽  
LYNN F. GLADDEN ◽  
RAYMOND E. GOLDSTEIN
Keyword(s):  
Magnetic Resonance ◽  
Spatial Resolution ◽  
Cross Sections ◽  
Cytoplasmic Streaming ◽  
Molecular Motor ◽  
Longitudinal Velocity ◽  
Quantitative Agreement ◽  
Chara Corallina ◽  
Magnetic Resonance Velocimetry ◽  
Streaming Flows

In the giant cylindrical cells found in Characean algae, multitudes of the molecular motor myosin transport the cytoplasm along opposing spiralling bands covering the inside of the cell wall, generating a helical shear flow in the large central vacuole. It has been suggested that such flows enhance mixing within the vacuole (van de Meent, Tuval & Goldstein, Phys. Rev. Lett., vol. 101, 2008, paper no. 178102) and thereby play a role in regulating metabolism. For this to occur the membrane that encloses the vacuole, namely the tonoplast, must transmit efficiently the hydrodynamic shear generated in the cytoplasm. Existing measurements of streaming flows are of insufficient spatial resolution and extent to provide tests of fluid mechanical theories of such flows and information on the shear transmission. Here, using magnetic resonance velocimetry (MRV), we present the first measurements of cytoplasmic streaming velocities in single living cells. The spatial variation of the longitudinal velocity field in cross-sections of internodal cells of Chara corallina is obtained with spatial resolution of 16 μm and is shown to be in quantitative agreement with a recent theoretical analysis (Goldstein, Tuval & van de Meent, Proc. Natl. Acad. Sci. USA, vol. 105, 2008, p. 3663) of rotational cytoplasmic streaming driven by bidirectional helical forcing in the cytoplasm, with direct shear transmission by the tonoplast. These results highlight the open problem of understanding tonoplast motion induced by streaming. Moreover, this study suggests the suitability of MRV in the characterization of streaming flows in a variety of eukaryotic systems and for microfluidic phenomena in general.

Parametric effects on the flow redistribution in ballooned bundles evaluated by magnetic resonance velocimetry

2021 ◽  
Vol 125 ◽  
pp. 110383
Author(s):  
A.V.S. Oliveira ◽  
D. Stemmelen ◽  
S. Leclerc ◽  
T. Glantz ◽  
A. Labergue ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Magnetic Resonance Velocimetry ◽  
Parametric Effects

Numerical Analysis of Branch Mechanical Response to Loading

2019 ◽  
Vol 45 (4) ◽  
Author(s):  
Barbora Vojáčková ◽  
Jan Tippner ◽  
Petr Horáček ◽  
Luděk Praus ◽  
Václav Sebera ◽  
...  
Keyword(s):  
Finite Element ◽  
Cross Sections ◽  
Mechanical Response ◽  
Mechanical Analysis ◽  
Beam Deflection ◽  
Design System ◽  
Elliptical Cross ◽  
Static Mechanical ◽  
The Difference ◽  
Tree Uprooting

Failure of a tree can be caused by a stem breakage, tree uprooting, or branch failure. While the pulling test is used for assessing the first two cases, there is no device-supported method to assess branch failure. A combination of the optical technique, pulling test, and deflection curve analysis could provide a device-supported tool for this kind of assessment. The aim of the work was to perform a structural analysis of branch response to static mechanical loading. The analyses were carried out by finite element simulations in ANSYS using beam tapered elements of elliptical cross-sections. The numerical analyses were verified by the pulling test combined with a sophisticated optical assessment of deflection evaluation. The Probabilistic Design System was used to find the parameters that influence branch mechanical response to loading considering the use of cantilever beam deflection for stability analysis. The difference in the branch’s deflection between the simulation and the experiment is 0.5% to 26%. The high variability may be explained by the variable modulus of the elasticity of branches. The finite element (FE) sensitivity analysis showed a higher significance of geometry parameters (diameter, length, tapering, elliptical cross-section) than material properties (elastic moduli). The anchorage rotation was found to be significant, implying that this parameter may affect the outcome in mechanical analysis of branch behavior. The branch anchorage can influence the deflection of the whole branch, which should be considered in stability assessment.

Magnetic Resonance Flow Analysis of Classic and Extracardiac Fontan Procedures: The Seesaw Sign

2004 ◽  
Vol 20 (5) ◽  
pp. 397-405 ◽  
Author(s):  
S. Bruce Greenberg ◽  
W. Robert Morrow ◽  
Michiaki Imamura ◽  
Jonathan Drummond-Webb
Keyword(s):  
Magnetic Resonance ◽  
Flow Analysis ◽  
Resonance Flow ◽  
Extracardiac Fontan

scholarly journals Three-dimensional magnetic resonance flow analysis in a ventricular assist device

2007 ◽  
Vol 134 (6) ◽  
pp. 1471-1476 ◽  
Author(s):  
Michael Markl ◽  
Christoph Benk ◽  
Dominik Klausmann ◽  
Aurelien F. Stalder ◽  
Alex Frydrychowicz ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Ventricular Assist Device ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Assist Device ◽  
Ventricular Assist ◽  
Resonance Flow

A Combined CFD/MRV Study of Flow Through a Pin Bank

2014 ◽  
Author(s):  
Mike Siekman ◽  
David Helmer ◽  
Wontae Hwang ◽  
Gregory Laskowski ◽  
Ek Tsoon Tan ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Velocity Field ◽  
Turbulence Model ◽  
Field Data ◽  
Peak Velocity ◽  
Velocity Profiles ◽  
Mean Velocity ◽  
Magnetic Resonance Velocimetry ◽  
Sst Turbulence Model ◽  
Flow Through

RANS and time averaged URANS simulations of a pin bank are compared quantitatively and qualitatively to full 3D mean velocity field data obtained using magnetic resonance velocimetry (MRV). The ability of the CFD to match MRV velocity profiles through the pin bank is evaluated using the SST turbulence model. Quantitative comparisons of the velocity profiles showed an overprediction of peak velocity by the CFD at the first pin rows, and a smaller oscillatory error that diminishes as it moves through the pins, resulting in better matching towards the exit.

Effect of Open- vs Closed-Cell Stent Design on Periprocedural Outcomes and Restenosis After Carotid Artery Stenting: A Systematic Review and Comprehensive Meta-analysis

2018 ◽  
Vol 25 (4) ◽  
pp. 523-533 ◽  
Author(s):  
Pavlos Texakalidis ◽  
Stefanos Giannopoulos ◽  
Damianos G. Kokkinidis ◽  
Giuseppe Lanzino
Keyword(s):  
Carotid Artery ◽  
Carotid Artery Stenting ◽  
Meta Analysis ◽  
Stent Design ◽  
Open Cell ◽  
Stent Restenosis ◽  
Closed Cell ◽  
Ischemic Attack ◽  
In Stent Restenosis

Purpose:To compare periprocedural complications and in-stent restenosis rates associated with open- vs closed-cell stent designs used in carotid artery stenting (CAS). Methods: A systematic search was conducted to identify all randomized and observational studies published in English up to October 31, 2017, that compared open- vs closed-cell stent designs in CAS. Identified studies were included if they reported the following outcomes: stroke, transient ischemic attack (TIA), myocardial infarction (MI), hemodynamic depression, new ischemic lesions detected on imaging, and death within 30 days, as well as the incidence of in-stent restenosis. A random-effects model meta-analysis was employed. Model results are reported as the odds ratio (OR) and 95% confidence interval (CI). The I2 statistic was used to assess heterogeneity. Results: Thirty-three studies (2 randomized trials) comprising 20, 291 patients (mean age 71.3±3.0 years; 74.6% men) were included. Patients in the open-cell stent group had a statistically significant lower risk of restenosis ⩾40% (OR 0.42, 95% CI 0.19 to 0.92; I2=0%) and ⩾70% (OR 0.23, 95% CI 0.10 to 0.52; I2=0%) at a mean follow-up of 24 months. No statistically significant differences were identified for periprocedural stroke, TIA, new ischemic lesions, MI, hemodynamic depression, or death within 30 days after CAS. Sensitivity analysis of the 2 randomized controlled trials only did not point to any significant differences either. Conclusion: Use of open-cell stent design in CAS is associated with a decreased risk for restenosis when compared to the closed-cell stent, without significant differences in periprocedural outcomes.

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