On the Use of In Vivo Measured Flow Rates as Boundary Conditions for Image-Based Hemodynamic Models of the Human Aorta

2011 ◽  
Author(s):  
Diego Gallo ◽  
Gianluca De Santis ◽  
Federica Negri ◽  
Daniele Tresoldi ◽  
Giovanna Rizzo ◽  
...  
Keyword(s):  
Blood Flow ◽  
Boundary Conditions ◽  
Rigid Wall ◽  
Patient Specific ◽  
Human Aorta ◽  
Computational Domain ◽  
Healthy Human ◽  
Flow Rates ◽  
Measured Flow

It has been demonstrated that computational fluid dynamics (CFD) have the potential to enhance the comprehension of the role played by hemodynamic factors involved in atherosclerosis. Recently, phase-contrast magnetic resonance imaging (PC-MRI) has emerged as an effective tool for providing accurate vascular geometries for CFD simulations and quantitative data on blood flow rates, which can be used to specify realistic boundary conditions (BCs). However, the application of acquired flow waveforms at boundaries is not straightforward, mainly (i) due to possible occurrences of phase shifts and attenuations of outflow with respect to inflow rate and (ii) due to the instantaneous mass conservation constraint, which is required in hemodynamic simulations with rigid wall models, but is not guaranteed in in vivo measurements. As an alternative, new boundary conditions schemes have been developed in an effort to consider the interaction between the computational domain and the upstream/downstream vasculature by coupling through-scale hemodynamic models [1]. However, the identification of the parameters of these simplified vascular models on a subject-specific base involves both pressure and flow rates measurements [2]. In this context, it is clear that the direct application of individual PC-MRI measured flow rates waveforms as BCs in patient-specific simulations should be preferred [3]. In order to overcome the limitations mentioned above, measured flow rates should be combined with stress-free conditions or fixed mass flow ratio (derived from the same set of PC-MRI data) between inlet and multiple outlet sections. However, prescribing different BCs at boundaries can affect the solutions of the equations governing blood flow [1]. For this reason, different strategies in combining outlet BCs could lead to different simulated hemodynamics. This work analyzes the influence of different possible strategies of applying PC-MRI measured flow rates on an image-based hemodynamic model of a healthy human aortic arch with supra-aortic vessels. A total of six flow simulations was carried out applying six different schemes for treating BCs at outlets. Three common wall shear stress (WSS)-based indicators of abnormal flow were considered and the sensitivity of these indicators to the outlet treatment strategy was evaluated.

On the Use of In Vivo Measured Flow Rates as Boundary Conditions for Image-Based Hemodynamic Models of the Human Aorta: Implications for Indicators of Abnormal Flow

2011 ◽  
Vol 40 (3) ◽  
pp. 729-741 ◽  
Author(s):  
D. Gallo ◽  
G. De Santis ◽  
F. Negri ◽  
D. Tresoldi ◽  
R. Ponzini ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
Human Aorta ◽  
Flow Rates ◽  
Measured Flow

Computational Study on the Effects of Peripheral Vessel Network on Blood Flow in the Arterial Circle of Willis

2007 ◽  
Author(s):  
Shigefumi Tokuda ◽  
Takeshi Unemura ◽  
Marie Oshima
Keyword(s):  
Numerical Simulation ◽  
Blood Flow ◽  
Boundary Conditions ◽  
Vascular System ◽  
Computational Study ◽  
Circulatory System ◽  
Biological Data ◽  
Patient Specific ◽  
Peripheral Vessel

Cerebrovascular disorder such as subarachnoid hemorrhage (SAH) is 3rd position of the cause of death in Japan [1]. Its initiation and growth are reported to depend on hemodynamic factors, particularly on wall shear stress or blood pressure induced by blood flow. In order to investigate the information on the hemodynamic quantities in the cerebral vascular system, the authors have been developing a computational tool using patient-specific modeling and numerical simulation [2]. In order to achieve an in vivo simulation of living organisms, it is important to apply appropriate physiological conditions such as physical properties, models, and boundary conditions. Generally, the numerical simulation using a patient-specific model is conducted for a localized region near the research target. Although the analysis region is only a part of the circulatory system, the simulation has to include the effects from the entire circulatory system. Many studies have carried out to derive the boundary conditions to model in vivo environment [3–5]. However, it is not easy to obtain the biological data of cerebral arteries due to head capsule.

Sensitivity of patient-specific numerical simulation of cerebal aneurysm hemodynamics to inflow boundary conditions

2007 ◽  
Vol 106 (6) ◽  
pp. 1051-1060 ◽  
Author(s):  
Prem Venugopal ◽  
Daniel Valentino ◽  
Holger Schmitt ◽  
J. Pablo Villablanca ◽  
Fernando Viñuela ◽  
...  
Keyword(s):  
Blood Flow ◽  
Shear Stress ◽  
Boundary Conditions ◽  
Numerical Simulations ◽  
Flow Rate ◽  
Artery Aneurysm ◽  
Blood Flow Rate ◽  
Patient Specific ◽  
Stress Distributions ◽  
Flow Rates

Object Due to the difficulty of obtaining patient-specific velocity measurements during imaging, many assumptions have to be made while imposing inflow boundary conditions in numerical simulations conducted using patient-specific, imaging-based cerebral aneurysm models. These assumptions can introduce errors, resulting in lack of agreement between the computed flow fields and the true blood flow in the patient. The purpose of this study is to evaluate the effect of the assumptions made while imposing inflow boundary conditions on aneurysmal hemodynamics. Methods A patient-based anterior communicating artery aneurysm model was selected for this study. The effects of various inflow parameters on numerical simulations conducted using this model were then investigated by varying these parameters over ranges reported in the literature. Specifically, we investigated the effects of heart and blood flow rates as well as the distribution of flow rates in the A1 segments of the anterior cerebral artery. The simulations revealed that the shear stress distributions on the aneurysm surface were largely unaffected by changes in heart rate except at locations where the shear stress magnitudes were small. On the other hand, the shear stress distributions were found to be sensitive to the ratio of the flow rates in the feeding arteries as well as to variations in the blood flow rate. Conclusions Measurement of the blood flow rate as well as the distribution of the flow rates in the patient's feeding arteries may be needed for numerical simulations to accurately reproduce the intraaneurysmal hemodynamics in a specific aneurysm in the clinical setting.

scholarly journals Computational Modeling of the Liver Arterial Blood Flow for Microsphere Therapy: Effect of Boundary Conditions

2020 ◽  
Vol 7 (3) ◽  
pp. 64
Author(s):  
Amirtahà Taebi ◽  
Rex M. Pillai ◽  
Bahman S. Roudsari ◽  
Catherine T. Vu ◽  
Emilie Roncali
Keyword(s):  
Blood Flow ◽  
Boundary Conditions ◽  
Hepatic Artery ◽  
Transarterial Embolization ◽  
Arterial Blood Flow ◽  
Patient Specific ◽  
Computational Domain ◽  
Arterial Tree ◽  
Arterial Blood ◽  
Therapy Effect

Transarterial embolization is a minimally invasive treatment for advanced liver cancer using microspheres loaded with a chemotherapeutic drug or radioactive yttrium-90 (90Y) that are injected into the hepatic arterial tree through a catheter. For personalized treatment, the microsphere distribution in the liver should be optimized through the injection volume and location. Computational fluid dynamics (CFD) simulations of the blood flow in the hepatic artery can help estimate this distribution if carefully parameterized. An important aspect is the choice of the boundary conditions imposed at the inlet and outlets of the computational domain. In this study, the effect of boundary conditions on the hepatic arterial tree hemodynamics was investigated. The outlet boundary conditions were modeled with three-element Windkessel circuits, representative of the downstream vasculature resistance. Results demonstrated that the downstream vasculature resistance affected the hepatic artery hemodynamics such as the velocity field, the pressure field and the blood flow streamline trajectories. Moreover, the number of microspheres received by the tumor significantly changed (more than 10% of the total injected microspheres) with downstream resistance variations. These findings suggest that patient-specific boundary conditions should be used in order to achieve a more accurate drug distribution estimation with CFD in transarterial embolization treatment planning.

scholarly journals Patient-specific computational haemodynamics associated with surgical creation of an arteriovenous fistula

2021 ◽  
Author(s):  
George Hyde-Linaker ◽  
Pauline Hall Barrientos ◽  
Sokratis Stoumpos ◽  
Asimina Kazakidi
Keyword(s):  
Blood Flow ◽  
Flow Rate ◽  
Disease Patient ◽  
Blood Flow Rate ◽  
Fold Increase ◽  
Transitional Flow ◽  
Patient Specific ◽  
Venous Anastomosis ◽  
End Stage

Abstract Despite arteriovenous fistulae (AVF) being the preferred vascular access for haemodialysis, high primary failure rates (30-70%) and low one-year patency rates (40-70%) hamper their use. The haemodynamics within the vessels of the fistula change significantly following surgical creation of the anastomosis and can be a surrogate of AVF success or failure. Computational fluid dynamics (CFD) can crucially predict AVF outcomes through robust analysis of a fistula’s haemodynamic patterns, which is impractical in-vivo. We present a proof-of-concept CFD framework for characterising the AVF blood flow prior and following surgical creation of a successful left radiocephalic AVF in a 20-year-old end-stage kidney disease patient. The reconstructed vasculature was generated utilising multiple contrast-enhanced magnetic resonance imaging (MRI) datasets. Large eddy simulations were conducted for establishing the extent of arterial and venous remodelling. Following anastomosis creation, a significant 2-3-fold increase in blood flow rate was induced downstream of the left subclavian artery. This was validated through comparison with post-AVF patient-specific phase-contrast data. The increased flow rate yielded an increase in time-averaged wall shear stress (TAWSS), a key marker of adaptive vascular remodelling. We have demonstrated TAWSS and oscillatory shear distributions of the transitional-flow in the venous anastomosis are predictive of AVF remodelling.

scholarly journals Major differences in noradrenaline action on lipolysis and blood flow rates in skeletal muscle and adipose tissue in vivo

Diabetologia ◽  
2005 ◽  
Vol 48 (5) ◽  
pp. 946-953 ◽  
Author(s):  
V. Quisth ◽  
S. Enoksson ◽  
E. Blaak ◽  
E. Hagström-Toft ◽  
P. Arner ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Blood Flow ◽  
Adipose Tissue ◽  
Flow Rates

Cyclic Breathing Simulations in Large-Scale Models of the Lung Airway From the Oronasal Opening to the Terminal Bronchioles

2014 ◽  
Vol 136 (10) ◽  
Author(s):  
D. Keith Walters ◽  
Greg W. Burgreen ◽  
Robert L. Hester ◽  
David S. Thompson ◽  
David M. Lavallee ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
Mass Flow ◽  
Flow Rate ◽  
Large Scale ◽  
Whole Body ◽  
Patient Specific ◽  
Computational Domain ◽  
Scale Models ◽  
Fully Coupled ◽  
Conducting Zone

Computational fluid dynamics (CFD) simulations were performed using large-scale models of the human lung airway and unsteady periodic breathing conditions. The computational domain included fully coupled representations of the orotracheal region and large conducting zone up to generation four (G4) obtained from patient-specific CT data, and the small conducting zone (to the 16th generation) obtained from a stochastically generated airway tree with statistically realistic morphological characteristics. A reduced-geometry airway model was used, in which several airway branches in each generation were truncated, and only select flow paths were retained to the 16th generation. The inlet and outlet flow boundaries corresponded to the oral opening, the physical inlet/outlet boundaries at the terminal bronchioles, and the unresolved airway boundaries created from the truncation procedure. The total flow rate was specified according to the expected ventilation pattern for a healthy adult male, which was supplied by the whole-body modeling software HumMod. The unsteady mass flow distribution at the distal boundaries was prescribed based on a preliminary steady-state simulation with an applied flow rate equal to the average flow rate during the inhalation phase of the breathing cycle. In contrast to existing studies, this approach allows fully coupled simulation of the entire conducting zone, with no need to specify distal mass flow or pressure boundary conditions a priori, and without the use of impedance or one-dimensional (1D) flow models downstream of the truncated boundaries. The results show that: (1) physiologically realistic flow is obtained in the model, in terms of cyclic mass conservation and approximately uniform pressure distribution in the distal airways; (2) the predicted alveolar pressure is in good agreement with correlated experimental data; and (3) the use of reduced-order geometry modeling allows accurate and efficient simulation of large-scale breathing lung flow, provided care is taken to use a physiologically realistic geometry and to properly address the unsteady boundary conditions.

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