scholarly journals Focal irregularities in 7-Tesla MRI of unruptured intracranial aneurysms as an indicator for areas of altered blood-flow parameters

2019 ◽  
Vol 47 (6) ◽  
pp. E7
Author(s):  
Matthias Millesi ◽  
Engelbert Knosp ◽  
Georg Mach ◽  
Johannes A. Hainfellner ◽  
Gerda Ricken ◽  
...  
Keyword(s):  
Blood Flow ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Field Strength ◽  
Vessel Wall ◽  
Intracranial Aneurysms ◽  
7 Tesla ◽  
Risk Of Rupture ◽  
Wall Shear ◽  
Cfd Analyses

OBJECTIVEIn the last several decades, various factors have been studied for a better evaluation of the risk of rupture in incidentally discovered intracranial aneurysms (IAs). With advanced MRI, attempts were made to delineate the wall of IAs to identify weak areas prone to rupture. However, the field strength of the MRI investigations was insufficient for reasonable image resolution in many of these studies. Therefore, the aim of this study was to analyze findings of IAs in ultra–high field MRI at 7 Tesla (7 T).METHODSPatients with incidentally found IAs of at least 5 mm in diameter were included in this study and underwent MRI investigations at 7 T. At this field strength a hyperintense intravascular signal can be observed on nonenhanced images with a brighter “rim effect” along the vessel wall. Properties of this rim effect were evaluated and compared with computational fluid dynamics (CFD) analyses.RESULTSOverall, 23 aneurysms showed sufficient image quality for further evaluation. In 22 aneurysms focal irregularities were identified within this rim effect. Areas of such irregularities showed significantly higher values in wall shear stress and vorticity compared to areas with a clearly visible rim effect (p = 0.043 in both).CONCLUSIONSA hyperintense rim effect along the vessel wall was observed in most cases. Focal irregularities within this rim effect showed higher values of the mean wall shear stress and vorticity when compared by CFD analyses. Therefore, these findings indicate alterations in blood flow in IAs within these areas.

A Numerical Multiscale Study of the Haemodynamics in an Image-Based Model of Human Carotid Artery Bifurcation

2009 ◽  
Author(s):  
Diego Gallo ◽  
Raffaele Ponzini ◽  
Filippo Consolo ◽  
Diana Massai ◽  
Luca Antiga ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Blood Flow ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Cardiovascular System ◽  
Vessel Wall ◽  
3D Model ◽  
Carotid Bifurcation ◽  
Wall Shear ◽  
Flow Division

The initiation and progression of vessel wall pathologies have been linked to disturbances of blood flow and altered wall shear stress. The development of computational techniques in fluid dynamics, together with the increasing performances of hardware and software allow to routinely solve problems on a virtual environment, helping to understand the role of biomechanics factors in the healthy and diseased cardiovascular system and to reveal the interplay of biology and local fluid dynamics nearly intractable in the past, opening to detailed investigation of parameters affecting disease progression. One of the major difficulties encountered when wishing to model accurately the cardiovascular system is that the flow dynamics of the blood in a specific vascular district is strictly related to the global systemic dynamics. The multiscale modelling approach for the description of blood flow into vessels consists in coupling a detailed model of the district of interest in the framework of a synthetic description of the surrounding areas of the vascular net [1]. In the present work, we aim at evaluating the effect of boundary conditions on wall shear stress (WSS) related vessel wall indexes and on bulk flow topology inside a carotid bifurcation. To do it, we coupled an image-based 3D model of carotid bifurcation (local computational domain), with a lumped parameters (0D) model (global domain) which allows for physiological mimicking of the haemodynamics at the boundaries of the 3D carotid bifurcation model here investigated. Two WSS based blood-vessel wall interaction descriptors, the Time Averaged WSS (TAWSS), and the Oscillating Shear Index (OSI) were considered. A specific Lagrangian-based “bulk” blood flow descriptor, the Helical Flow Index (HFI) [2], was calculated in order to get a “measure” of the helical structure in the blood flow. In a first analysis the effects of the coupled 0D models on the 3D model are evaluated. The results obtained from the multiscale simulation are compared with the results of simulations performed using the same 3D model, but imposing a flow rate at internal carotid (ICA) outlet section equal to the maximum (60%) and the minimum (50%) flow division obtained out from ICA in the multiscale model simulation (the presence of the coupled 0D model gives variable internal/external flow division ratio during the cardiac cycle), and a stress free condition on the external carotid (ECA).

scholarly journals Shear stress and aneurysms: a review

2019 ◽  
Vol 47 (1) ◽  
pp. E2 ◽  
Author(s):  
Brittany Staarmann ◽  
Matthew Smith ◽  
Charles J. Prestigiacomo
Keyword(s):  
Endothelial Cells ◽  
Blood Flow ◽  
Shear Stress ◽  
Smooth Muscle ◽  
Wall Shear Stress ◽  
Smooth Muscle Cells ◽  
Frictional Force ◽  
Vessel Wall ◽  
Risk Of Rupture ◽  
Aneurysm Growth

Wall shear stress, the frictional force of blood flow tangential to an artery lumen, has been demonstrated in multiple studies to influence aneurysm formation and risk of rupture. In this article, the authors review the ways in which shear stress may influence aneurysm growth and rupture through changes in the vessel wall endothelial cells, smooth-muscle cells, and surrounding adventitia, and they discuss shear stress–induced pathways through which these changes occur.

Computational Modeling of Non-Newtonian Blood Flow Through Stenosed Arteries in the Presence of Magnetic Field

2013 ◽  
Vol 135 (11) ◽  
Author(s):  
Aiman Alshare ◽  
Bourhan Tashtoush ◽  
Hossam H. El-Khalil
Keyword(s):  
Magnetic Field ◽  
Blood Flow ◽  
Shear Stress ◽  
Pressure Drop ◽  
Wall Shear Stress ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Stenosed Artery ◽  
Flow Through ◽  
Wall Shear

Steady flow simulations of blood flow in an axisymmetric stenosed artery, subjected to a static magnetic field, are performed to investigate the influence of artery size, magnetic field strength, and non-Newtonian behavior on artery wall shear stress and pressure drop in the stenosed section. It is found that wall shear stress and pressure drop increase by decreasing artery size, assuming non-Newtonian fluid, and increasing magnetic field strength. In the computations, the shear thinning behavior of blood is accounted for by the Carreau–Yasuda model. Computational results are compared and found to be inline with available experimental data.

Basic study on estimation method of wall shear stress in common carotid artery using blood flow imaging

2020 ◽  
Vol 59 (SK) ◽  
pp. SKKE16 ◽  
Author(s):  
Ryo Nagaoka ◽  
Kazuma Ishikawa ◽  
Michiya Mozumi ◽  
Magnus Cinthio ◽  
Hideyuki Hasegawa
Keyword(s):  
Blood Flow ◽  
Shear Stress ◽  
Carotid Artery ◽  
Wall Shear Stress ◽  
Common Carotid Artery ◽  
Estimation Method ◽  
Flow Imaging ◽  
Basic Study ◽  
Blood Flow Imaging ◽  
Wall Shear

Mathematical analysis of two-phase blood flow through a stenosed curved artery with hematocrit and temperature dependent viscosity

2021 ◽  
Author(s):  
Chandan Kumawat ◽  
Bhupendra Kumar Sharma ◽  
Khalid Saad Mekheimer
Keyword(s):  
Blood Flow ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Mathematical Study ◽  
Temperature Dependent ◽  
Two Phase ◽  
Temperature Dependent Viscosity ◽  
Linear Temperature ◽  
Wall Shear ◽  
Dependent Viscosity

Abstract A two-phase blood flow model is considered to analyze the fluid flow and heat transfer in a curved tube with time-variant stenosis. In both core and plasma regions, the variable viscosity model ( Hematocrit and non linear temperature-dependent, respectively) is considered. A toroidal coordinate system is considered to describe the governing equations. The perturbation technique in terms of perturbation parameter ε is used to obtain the temperature profile of blood flow. In order to find the velocity, wall shear stress and impedance profiles, a second-order finite difference method is employed with the accuracy of 10−6 in the each iteration. Under the conditions of fully-developed flow and mild stenosis, the significance of various physical parameters on the blood velocity, temperature, wall shear stress (WSS) and impedance are investigated with the help of graphs. A validation of our results has been presented and comparison has been made with the previously published work and present study, and it revels the good agreement with published work. The present mathematical study suggested that arterial curvature increase the fear of deposition of plaque (atherosclerosis), while, the use of thermal radiation in heat therapies lowers this risk. The positive add in the value of λ1 causes to increase in plasma viscosity; as a result, blood flow velocity in the stenosed artery decreases due to the assumption of temperature-dependent viscosity of the plasma region. Clinical researchers and biologists can adopt the present mathematical study to lower the risk of lipid deposition, predict cardiovascular disease risk and current state of disease by understanding the symptomatic spectrum, and then diagnose patients based on the risk.

A New Ultrasonographic Instrument for Measuring Vessel Wall Shear Stress: Comparison to a Mathematical Model in Essential Hypertensives

1996 ◽  
pp. 403-407 ◽  
Author(s):  
Moreno Bardelli ◽  
Renzo Carretta ◽  
Domenico Dotti ◽  
Bruno Fabris ◽  
Fabio Fischetti ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Vessel Wall ◽  
Measuring Vessel ◽  
Wall Shear

scholarly journals Numerical Simulation of Dispersed Particle-Blood Flow in the Stenosed Coronary Arteries

2018 ◽  
Vol 2018 ◽  
pp. 1-16 ◽  
Author(s):  
Mongkol Kaewbumrung ◽  
Somsak Orankitjaroen ◽  
Pichit Boonkrong ◽  
Buraskorn Nuntadilok ◽  
Benchawan Wiwatanapataphee
Keyword(s):  
Numerical Simulation ◽  
Blood Flow ◽  
Shear Stress ◽  
Coronary Artery ◽  
Pressure Drop ◽  
Wall Shear Stress ◽  
Stokes Equations ◽  
Spherical Shape ◽  
Shear Stresses ◽  
Wall Shear

A mathematical model of dispersed bioparticle-blood flow through the stenosed coronary artery under the pulsatile boundary conditions is proposed. Blood is assumed to be an incompressible non-Newtonian fluid and its flow is considered as turbulence described by the Reynolds-averaged Navier-Stokes equations. Bioparticles are assumed to be spherical shape with the same density as blood, and their translation and rotational motions are governed by Newtonian equations. Impact of particle movement on the blood velocity, the pressure distribution, and the wall shear stress distribution in three different severity degrees of stenosis including 25%, 50%, and 75% are investigated through the numerical simulation using ANSYS 18.2. Increasing degree of stenosis severity results in higher values of the pressure drop and wall shear stresses. The higher level of bioparticle motion directly varies with the pressure drop and wall shear stress. The area of coronary artery with higher density of bioparticles also presents the higher wall shear stress.

scholarly journals Evaluation of Aortic Blood Flow and Wall Shear Stress in Aortic Stenosis and Its Association With Left Ventricular Remodeling

2016 ◽  
Vol 9 (3) ◽  
Author(s):  
Florian von Knobelsdorff-Brenkenhoff ◽  
Achudhan Karunaharamoorthy ◽  
Ralf Felix Trauzeddel ◽  
Alex J. Barker ◽  
Edyta Blaszczyk ◽  
...  
Keyword(s):  
Blood Flow ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Aortic Stenosis ◽  
Ventricular Remodeling ◽  
Left Ventricular Remodeling ◽  
Left Ventricular ◽  
Aortic Blood Flow ◽  
Aortic Blood ◽  
Wall Shear
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