On the relevance of boundary conditions and viscosity models in blood flow simulations in patient‐specific aorto‐coronary bypass models

Model verification, validation, and uncertainty quantification are essential procedures to estimate errors within cardiovascular flow modeling, where acceptable confidence levels are needed for clinical reliability. While more turbulent-like studies are frequently observed within the biofluid community, practical modeling guidelines are scarce. Verification procedures determine the agreement between the conceptual model and its numerical solution by comparing for example, discretization and phase-averaging-related errors of specific output parameters. This computational fluid dynamics (CFD) study presents a comprehensive and practical verification approach for pulsatile turbulent-like blood flow predictions by considering the amplitude and shape of the turbulence-related tensor field using anisotropic invariant mapping. These procedures were demonstrated by investigating the Reynolds stress tensor characteristics in a patient-specific aortic coarctation model, focusing on modeling-related errors associated with the spatiotemporal resolution and phase-averaging sampling size. Findings in this work suggest that attention should also be put on reducing phase-averaging related errors, as these could easily outweigh the errors associated with the spatiotemporal resolution when including too few cardiac cycles. Also, substantially more cycles are likely needed than typically reported for these flow regimes to sufficiently converge the phase-instant tensor characteristics. Here, higher degrees of active fluctuating directions, especially of lower amplitudes, appeared to be the most sensitive turbulence characteristics.

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Learning Patient-Specific Lumped Models for Interactive Coronary Blood Flow Simulations

Lecture Notes in Computer Science - Medical Image Computing and Computer-Assisted Intervention -- MICCAI 2015 ◽

10.1007/978-3-319-24571-3_52 ◽

2015 ◽

pp. 433-441 ◽

Cited By ~ 7

Author(s):

Hannes Nickisch ◽

Yechiel Lamash ◽

Sven Prevrhal ◽

Moti Freiman ◽

Mani Vembar ◽

...

Keyword(s):

Blood Flow ◽

Coronary Blood Flow ◽

Patient Specific ◽

Flow Simulations ◽

Lumped Models

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Realistic and patient specific blood flow simulations

Computer Methods in Biomechanics & Biomedical Engineering ◽

10.1080/10255840701479867 ◽

2007 ◽

Vol 10 (sup1) ◽

pp. 175-176

Author(s):

R. Moreno ◽

F. Nicoud ◽

H. Rousseau

Keyword(s):

Blood Flow ◽

Patient Specific ◽

Flow Simulations

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

ASME 2007 Summer Bioengineering Conference ◽

10.1115/sbc2007-176706 ◽

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.

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Development of a Numerical Model for Micro-Scale Blood Flow Simulation Using GPGPU

ASME 2012 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2012-80028 ◽

2012 ◽

Author(s):

Naoki Takeishi ◽

Yohsuke Imai ◽

Keita Nakaaki ◽

Takuji Ishikawa ◽

Takami Yamaguchi

Keyword(s):

Blood Flow ◽

Gpu Computing ◽

Flow Simulation ◽

Patient Specific ◽

Immersed Boundary ◽

Processing Unit ◽

Computational Domain ◽

Membrane Mechanics ◽

Flow Simulations ◽

Micro Scale

Computational fluid dynamics (CFD) study of the behavior of red blood cells (RBCs) in flow provides us informative insight into the mechanics of blood flow in microvessels. However, the size of computational domain is limited due to computational expense. Recently, we proposed a graphics processing unit (GPU) computing method for patient-specific pulmonary airflow simulations (Miki et al., in press). In this study, we extend this method to micro-scale blood flow simulations, where a lattice Boltzmann method (LBM) of fluid mechanics is coupled with a finite element method (FEM) of membrane mechanics by an immersed boundary method (IBM). We also present validation and performance of our method for micro-scale blood flow simulations.

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Computational Modeling of Shear-Based Hemolysis Caused by Renal Obstruction

Journal of Biomechanical Engineering ◽

10.1115/1.4005850 ◽

2012 ◽

Vol 134 (2) ◽

Cited By ~ 12

Author(s):

Polina A. Segalova ◽

K. T. Venkateswara Rao ◽

Christopher K. Zarins ◽

Charles A. Taylor

Keyword(s):

Blood Flow ◽

Boundary Conditions ◽

Renal Artery ◽

Aortic Aneurysms ◽

Cfd Modeling ◽

Patient Specific ◽

Shear Stresses ◽

Baseline Model ◽

Implantable Medical Devices ◽

Renal Obstruction

As endovascular treatment of abdominal aortic aneurysms (AAAs) gains popularity, it is becoming possible to treat certain challenging aneurysmal anatomies with endografts relying on suprarenal fixation. In such anatomies, the bare struts of the device may be placed across the renal artery ostia, causing partial obstruction to renal artery blood flow. Computational fluid dynamics (CFD) was used to simulate blood flow from the aorta to the renal arteries, utilizing patient-specific boundary conditions, in three patient models and calculate the degree of shear-based blood damage (hemolysis). We used contrast-enhanced computed tomography angiography (CTA) data from three AAA patients who were treated with a novel endograft to build patient-specific models. For each of the three patients, we constructed a baseline model and endoframe model. The baseline model was a direct representation of the patient’s 30-day post-operative CTA data. This model was then altered to create the endoframe model, which included a ring of metallic struts across the renal artery ostia. CFD was used to simulate blood flow, utilizing patient-specific boundary conditions. Pressures, flows, shear stresses, and the normalized index of hemolysis (NIH) were quantified for all patients. The overall differences between the baseline and endoframe models for all three patients were minimal, as measured though pressure, volumetric flow, velocity, and shear stress. The average NIH across the three baseline and endoframe models was 0.002 and 0.004, respectively. Results of CFD modeling show that the overall disturbance to flow caused by the presence of the endoframe struts is minimal. The magnitude of the NIH in all models was well below the accepted design and safety threshold for implantable medical devices that interact with blood flow.

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Volumetric Flow at the Supraceliac and Infrarenal Levels in Patients With Abdominal Aortic Aneurysm: Waveforms and Allometric Scaling Relationships

ASME 2009 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2009-204269 ◽

2009 ◽

Cited By ~ 1

Author(s):

Andrea S. Les ◽

Janice J. Yeung ◽

Phillip M. Young ◽

Robert J. Herfkens ◽

Ronald L. Dalman ◽

...

Keyword(s):

Blood Flow ◽

Abdominal Aortic Aneurysm ◽

Aortic Aneurysm ◽

Boundary Conditions ◽

Computational Simulation ◽

Critical Role ◽

Healthy Person ◽

Patient Specific ◽

Hemodynamic Forces ◽

Abdominal Aortic

Hemodynamic forces are thought to play a critical role in abdominal aortic aneurysm (AAA) formation and growth, as well as in the migration and failure of aortic stent grafts. Computational simulation of blood flow enables the study of such hemodynamic forces; however, these simulations require accurate geometries and boundary conditions, usually in the form of flow and pressure data at specific locations. Although hundreds of computed tomography (CT) and magnetic resonance (MR) imaging studies of AAA geometry are performed daily in the clinical setting, flow information is difficult to obtain: It is not possible to reliably measure flow using CT, and while phase-contrast MRI (PC-MRI) can measure velocities, it is rarely used clinically for AAA patients. As a result, many AAA blood flow simulations use highly resolved patient-specific geometries, but may utilize literature-derived flows for inlet boundary conditions from a single, unrelated, sometimes healthy person of dissimilar body mass.

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