Estimation of endothelial shear stress in atherosclerotic lesions detected by intravascular ultrasound using computational fluid dynamics from coronary CT scans with a pulsatile blood flow and an individualized blood viscosity

2021 ◽  
pp. 1-14
Author(s):  
Adrian Curta ◽  
Ahmad Jaber ◽  
Johannes Rieber ◽  
Holger Hetterich
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Shear Stress ◽  
Coronary Arteries ◽  
Blood Viscosity ◽  
Flow Profile ◽  
Cfd Simulations ◽  
Coronary Ct ◽  
Endothelial Shear Stress

INTRODUCTION: Endothelial shear stress (ESS) is a local hemodynamic factor that is dependent on vessel geometry and influences the process of atherogenesis. As in vivo measurements of ESS are not possible, it must be calculated using computational fluid dynamics (CFD). In this feasibility study we explore CFD-models generated from coronary CT-angiography (CCTA) using an individualised blood viscosity and a pulsatile flow profile derived from in vivo measurements. MATERIALS AND METHODS: We retrospectively recruited 25 consecutive patients who received a CCTA followed by a coronary angiography including intravascular ultrasound (IVUS) and generated 3D models of the coronary arteries from the CT-datasets. We then performed CFD-simulations on these models. Hemodynamically non-relevant stenosis were identified in IVUS. They were isolated in the CFD-model and separated longitudinally into a half with atherosclerotic lesion (AL) and one without (NAL). ESS was measured and compared for both halves. RESULTS: After excluding vessels with no IVUS data or relevant stenosis we isolated 31 hemodynamically non-relevant excentric AL from a total of 14 vessels. AL segments showed consistently significantly lower ESS when compared to their corresponding NAL segments when regarding minimum (0.9 Pa, CI [0.6, 1.2] vs. 1.3 Pa, CI [0.9, 1.8]; p = 0.004), mean (5.0 Pa, CI [3.4, 6.0] vs. 6.7 Pa, CI [5.5, 8.4]; p = 0.008) and maximum ESS values (12.4 Pa, CI [8.6, 14.6] vs. 19.6 Pa, CI [12.4, 21.0]; p = 0.005). Qualitatively ESS was lower on the inside of bifurcations and curvatures. CONCLUSION: CFD simulations of coronary arteries from CCTA with an individualised flow profile and blood viscosity are feasible and could provide further prognostic information and a better risk stratification in coronary artery disease. Further prospective studies are needed to investigate this claim.

Abstract 2800: Assessment of Computational Fluid Dynamics to Calculate Individual Coronary Wall Shear Stress In-Vivo

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Johannes Rieber ◽  
Thomas Redel ◽  
Holger Hetterich ◽  
Tobias Potzger ◽  
Konstantin Nikolaou ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Shear Stress ◽  
Coronary Angiography ◽  
Wall Shear Stress ◽  
Radio Frequency ◽  
Intravascular Ultrasound ◽  
Coronary Arteries ◽  
Wall Shear

Beyond classic risk parameters non physiologic or oscillating wall shear stress (WSS) has been proven to act as a local factor for initiation and progression of atherosclerosis as well as for plaque rupture. Direct measurement of WSS in-vivo is difficult and restricted to animal models. Computational fluid dynamics (CFD) is a validated tool to compute flow parameters and WSS. For this purpose an exact model of the underlying patient specific geometry of the coronary tree is a prerequisite. Using 3D-IVUS or modern multislice computed tomographic coronary angiography (CTA) with submilimeter resolution these data can be provided. The aim of this study was to 1.) demonstrate feasibility of in-vivo CFD calculation of human coronaries based on CTA and 2.) to correlate the findings with radio frequency tissue information derived by intravascular ultrasound. We prospectively included 10 patients with suspected coronary artery disease who received CTA (Dual source 64 slice CT) and invasive conventional coronary angiography. Intravascular ultrasound and ECG-triggered radio frequency analysis (VH) was attempted in all three epicardial vessels. In the CTA-dataset the coronaries were segmented and a mesh model for CFD was generated. CFD calculations were performed using a commercial available software package with laminar flow and blood as a Newtonian fluid as boundary conditions. Coronary models were stationary with rigid vessel walls, while the pulsatile inflow characteristics was derived from invasive Doppler velocity measurement. Flow pattern calculations, vessel wall shear stress and IVUS analysis were successfully performed in 24/30 and 17/30 coronary arteries. The presence of high shear stress and non turbulent flow was inversely correlated with the presence of plaque as determined by intravascular ultrasound. No correlation of any CFD parameter with the radio frequency tissue information could yet be observed. The findings of the present study demonstrate the feasibility of assessing fluid tissue interactions in human coronary arteries using CTA and its correlation to invasive findings. The possible impact of CFD parameters on risk- and treatment stratification has to be determined in a large scale prospective trial.

scholarly journals Aerodynamic effects of inferior turbinate surgery on nasal airflow--a computational fluid dynamics model

2010 ◽  
Vol 48 (4) ◽  
pp. 394-400
Author(s):  
X.B. Chen ◽  
S.C. Leong ◽  
H.P. Lee ◽  
V.F.H. Chong ◽  
D.Y. Wang
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Middle Turbinate ◽  
Inferior Turbinate ◽  
Atrophic Rhinitis ◽  
Single Individual ◽  
Cfd Simulations ◽  
Wall Shear

BACKGROUND: Turbinate reduction surgery may be indicated for inferior turbinate enlargement when conservative treatment fails. The aim of this study was to evaluate the effects of inferior turbinate surgery on nasal aerodynamics using computational fluid dynamics (CFD) simulations. METHODS: CFD simulations were performed for the normal nose, enlarged inferior turbinate and following three surgical procedures: (1) resection of the lower third free edge of the inferior turbinate, (2) excision of the head of the inferior turbinate and (3) radical inferior turbinate resection. The models were constructed from MRI scans of a healthy human subject and a turbulent flow model was used for the numerical simulation. The consequences of the three turbinate surgeries were compared with originally healthy nasal model as well as the one with severe nasal obstruction. RESULTS: In the normal nose, the bulk of streamlines traversed the common meatus adjacent to the inferior and middle turbinate in a relatively vortex free flow. When the inferior turbinate was enlarged, the streamlines were directed superiorly at higher velocity and increased wall shear stress in the nasopharynx. Of the three surgical techniques simulated, wall shear stress and intranasal pressures achieved near-normal levels after resection of the lower third. In addition, airflow streamlines and turbulence improved although it did not return to normal conditions. As expected, radical turbinate resection resulted in intra-nasal aerodynamics of atrophic rhinitis demonstrated in previous CFD studies. CONCLUSION: There is little evidence that inspired air is appropriately conditioned following radical turbinate surgery. Partial reduction of the hypertropic turbinate results in improved nasal aerodynamics, which was most evident following resection of the lower third. The results were based on a single individual and cannot be generalised without similar studies in other subjects.

Relation Between Wall Shear Stress and Plaque Necrotic Core in the Left Coronary Arteries of Patients Using Intravascular Ultrasound and Computational Fluid Dynamics

2008 ◽  
Author(s):  
Jin Suo ◽  
Michael McDaniel ◽  
Habib Samady ◽  
Don Giddens
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Intravascular Ultrasound ◽  
Coronary Arteries ◽  
Plaque Rupture ◽  
Necrotic Core ◽  
Elastic Membrane ◽  
Wall Shear

Atherosclerosis is a disease characterized by arterial plaques that include several components of which the necrotic core has been recognized as an important indicator of the likelihood of plaque rupture [1]. In the present study, the relation of hemodynamic wall shear stress (WSS) to necrotic core localization in the left coronary artery of patients was investigated using intravascular ultrasound (IVUS) and computational fluid dynamics (CFD). An innovative 3D measuring technique was developed and was successfully used to reconstruct coronary arteries in patients based on angiographic images and echo ultrasound slices from IVUS. The reconstruction includes lumen, external elastic membrane (EEM) and spatial distribution of plaque components such as fibrous tissue, necrotic core and calcium. WSS distribution in the vessel segment was computed by CFD, and the relative locations of necrotic core and WSS were determined. Results to date support the hypothesis that a greater necrotic core in coronary plaques is associated with areas of low WSS. The methodology developed has implications for the study of plaque progression and the prediction of likelihood of plaque rupture.

Patient-Specific Stented Coronary Bifurcations: Numerical Analysis of Near-Wall Quantities and the Bulk Flow

2013 ◽  
Author(s):  
Claudio Chiastra ◽  
Stefano Morlacchi ◽  
Diego Gallo ◽  
Umberto Morbiducci ◽  
Rubén Cárdenes ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Shear Stress ◽  
Coronary Arteries ◽  
Fluid Dynamic ◽  
Patient Specific ◽  
Wall Region ◽  
Stent Restenosis ◽  
Local Measurements ◽  
In Stent Restenosis

The mechanisms and the causes of the in-stent restenosis process in coronary arteries are not fully understood. One of the most relevant phenomena, which seems to be associated to this process, is an altered hemodynamics in the stented wall region [1]. In vivo local measurements of velocities and their gradients in human coronary arteries are very difficult and can hardly be applied to successfully investigate the fluid dynamic field [1]. Alternatively, virtual models of blood flow in patient-specific coronary arteries allow the study of local fluid dynamics and the computation of the wall shear stress (WSS) and other quantities which can be related to the risk of restenosis.

scholarly journals Human upper-airway respiratory airflow: In vivo comparison of computational fluid dynamics simulations and hyperpolarized 129Xe phase contrast MRI velocimetry

PLoS ONE ◽  
2021 ◽  
Vol 16 (8) ◽  
pp. e0256460
Author(s):  
Qiwei Xiao ◽  
Neil J. Stewart ◽  
Matthew M. Willmering ◽  
Chamindu C. Gunatilaka ◽  
Robert P. Thomen ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Phase Contrast ◽  
Upper Airway ◽  
Breathing Patterns ◽  
Cfd Simulations ◽  
Airflow Velocity ◽  
Obstructive Sleep ◽  
Respiratory Airflow

Computational fluid dynamics (CFD) simulations of respiratory airflow have the potential to change the clinical assessment of regional airway function in health and disease, in pulmonary medicine and otolaryngology. For example, in diseases where multiple sites of airway obstruction occur, such as obstructive sleep apnea (OSA), CFD simulations can identify which sites of obstruction contribute most to airway resistance and may therefore be candidate sites for airway surgery. The main barrier to clinical uptake of respiratory CFD to date has been the difficulty in validating CFD results against a clinical gold standard. Invasive instrumentation of the upper airway to measure respiratory airflow velocity or pressure can disrupt the airflow and alter the subject’s natural breathing patterns. Therefore, in this study, we instead propose phase contrast (PC) velocimetry magnetic resonance imaging (MRI) of inhaled hyperpolarized 129Xe gas as a non-invasive reference to which airflow velocities calculated via CFD can be compared. To that end, we performed subject-specific CFD simulations in airway models derived from 1H MRI, and using respiratory flowrate measurements acquired synchronously with MRI. Airflow velocity vectors calculated by CFD simulations were then qualitatively and quantitatively compared to velocity maps derived from PC velocimetry MRI of inhaled hyperpolarized 129Xe gas. The results show both techniques produce similar spatial distributions of high velocity regions in the anterior-posterior and foot-head directions, indicating good qualitative agreement. Statistically significant correlations and low Bland-Altman bias between the local velocity values produced by the two techniques indicates quantitative agreement. This preliminary in vivo comparison of respiratory airway CFD and PC MRI of hyperpolarized 129Xe gas demonstrates the feasibility of PC MRI as a technique to validate respiratory CFD and forms the basis for further comprehensive validation studies. This study is therefore a first step in the pathway towards clinical adoption of respiratory CFD.

scholarly journals Hemodynamic Changes in the Carotid Artery after Infusion of Normal Saline Using Computational Fluid Dynamics

Diagnostics ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 473
Author(s):  
Ui Yun Lee ◽  
Chul In Kim ◽  
Gyung Ho Chung ◽  
Jinmu Jung ◽  
Hyo Sung Kwak
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Shear Stress ◽  
Shear Rate ◽  
Carotid Artery ◽  
Normal Saline ◽  
Blood Viscosity ◽  
Internal Carotid ◽  
Hemodynamic Changes ◽  
Before And After

Purpose: To study the effect of the infusion of normal saline on hemodynamic changes in healthy volunteers using computational fluid dynamics (CFD) simulation. Methods: Eight healthy subjects participated and 16 carotid arteries were used for the CFD analysis. A one-liter intravenous infusion of normal saline was applied to the participants to observe the hemodynamic variations. Blood viscosity was measured before and after the injection of normal saline to apply the blood properties on the CFD modeling. Blood viscosity, shear rate, and wall shear stress were visually and quantitatively shown for the comparison between before and after the infusion of normal saline. Statistical analyses were performed to confirm the difference between the before and after groups. Results: After the infusion of normal saline, decreased blood viscosity was observed in the whole carotid artery. At the internal carotid artery, the recirculation zone with low intensity was found after the injection of normal saline. Increased shear rate and reduced wall shear stress was observed at the carotid bifurcation and internal carotid artery. The hemodynamic differences between before and after groups were statistically significant. Conclusions: The infusion of normal saline affected not only the overall changes of blood flow in the carotid artery but also the decrease of blood viscosity.

scholarly journals A Computational Fluid Dynamics Protocol for The Hemodynamic Analysis of a Microfluidic Model of Thrombosis

2021 ◽  
Author(s):  
Yunduo Charles Zhao ◽  
Sarah Elizabeth Keogh ◽  
Parham Vatankhah ◽  
Renee Ellen Preketes-Tardiani ◽  
Lining Arnold Ju
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Shear Stress ◽  
Experimental Analysis ◽  
Microfluidic Channels ◽  
Cfd Simulations ◽  
Disturbed Flow ◽  
Computational Fluid Dynamics Cfd ◽  
Time Observation ◽  
Real Time Observation

Abstract Thrombosis is both attributed to biochemical agonists and mechanical stresses applied to platelets. Whilst the effect of biochemical agonists has been extensively studied, the mechanosensitive factors remain poorly defined. Stenotic microfluidic channels mimic the narrowing vessels, providing the real-time observation of platelets under disturbed flow. Though the experimental analysis of platelets in disturbed flow confirms the mechanosensitive behavior of platelets, it cannot explicate detailed thresholds for platelet activation. Computational Fluid Dynamics (CFD) could be utilized alongside experimental analysis to characterize thresholds for platelet behavior under imposed shear stress. CFD simulations, however, are prone to uncertainties and errors which should be minimized to obtain compelling results. Hereby, we have presented a CFD protocol for researchers in the field of microfluidic and hemodynamic studies.

Sign in / Sign up

Export Citation Format

Share Document