Effect of Patient-Specific Aorta Wall Properties on Hemodynamic Parameters

Background and Purpose: Recent studies have suggested that MR-vessel wall imaging (VWI) or computational fluid dynamics (CFD) could evaluate aneurysm wall features in unruptured intracranial aneurysms (UIAs). The combination of these modalities might be comprehensive and help better understanding of the pathophysiology of aneurysm wall. This study was performed to disclose the relationship between VWI and hemodynamic characteristics evaluated by CFD. Methods: From April 2017 through May 2019, a total of 36 microsurgically-treated UIAs preoperatively underwent VWI and CFD were reviewed. Three-dimensional T1-weighted fast spin-echo sequences were obtained before and after injection of contrast medium, and aneurysm wall enhancement (AWE) was evaluated. CFD was carried out using patient specific geometry models from three-dimensional CT angiography. Morphological variables, intraoperative inspection and hemodynamic parameters were statistically analyzed between enhanced and nonenhanced wall of UIAs. Fourteen UIAs were available for histopathological examination. Results: In morphological variables, maximum diameter and irregularity were associated with AWE (p=0.02, respectively). AWE lesions corresponded to intraoperatively inspected atherosclerotic lesions of UIAs (sensitivity, 0.90; specificity, 0.79). Among hemodynamic parameters, oscillatory velocity index that suggests the directional changes of the flow velocity was significantly higher in UIAs with AWE (p=0.02). Histopathologic studies revealed that wall thickening accompanied by atherosclerosis, neovascularization, and macrophage infiltration corresponded to AWE lesions, while UIAs without AWE demonstrated various histopathological findings such as myointimal hyperplasia or thinning wall with loss of mural cells and wall degeneration. Conclusions: Pathophysiology of AWE could be explained as atherosclerotic changes with inflammation presumably associated with aberrant flow conditions in irregular UIAs. VWI and CFD are complementarily valuable imaging techniques to understand an aneurysm wall pathophysiology.

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Image-Guided Fluid-Structure Interaction Simulation of Transvalvular Hemodynamics: Quantifying the Effects of Varying Aortic Valve Leaflet Thickness

Fluids ◽

10.3390/fluids4030119 ◽

2019 ◽

Vol 4 (3) ◽

pp. 119 ◽

Cited By ~ 4

Author(s):

Anvar Gilmanov ◽

Alexander Barker ◽

Henryk Stolarski ◽

Fotis Sotiropoulos

Keyword(s):

Blood Flow ◽

Aortic Valve ◽

Heart Valve ◽

Fluid Structure Interaction ◽

Maximum Velocity ◽

Patient Specific ◽

Hemodynamic Parameters ◽

Orifice Area ◽

Fluid Structure ◽

Structure Interaction

When flow-induced forces are altered at the blood vessel, maladaptive remodeling can occur. One reason such remodeling may occur has to do with the abnormal functioning of the aortic heart valve due to disease, calcification, injury, or an improperly-designed prosthetic valve, which restricts the opening of the valve leaflets and drastically alters the hemodynamics in the ascending aorta. While the specifics underlying the fundamental mechanisms leading to changes in heart valve function may differ from one cause to another, one common and important change is in leaflet stiffness and/or mass. Here, we examine the link between valve stiffness and mass and the hemodynamic environment in aorta by coupling magnetic resonance imaging (MRI) with high-resolution fluid–structure interaction (FSI) computational fluid dynamics to simulate blood flow in a patient-specific model. The thoracic aorta and a native aortic valve were re-constructed in the FSI model from the MRI data and used for the simulations. The effect of valve stiffness and mass is parametrically investigated by varying the thickness (h) of the leaflets (h = 0.6, 2, 4 mm). The FSI simulations were designed to investigate systematically progressively higher levels of valve stiffness by increasing valve thickness and quantifying hemodynamic parameters known to be linked to aortopathy and valve disease. The computed results reveal dramatic differences in all hemodynamic parameters: (1) the geometric orifice area (GOA), (2) the maximum velocity V max of the jet passing through the aortic orifice area, (3) the rate of energy dissipation E ˙ diss ( t ) , (4) the total loss of energy E diss , (5) the kinetic energy of the blood flow E kin ( t ) , and (6) the average magnitude of vorticity Ω a ( t ) , illustrating the change in hemodynamics that occur due to the presence of aortic valve stenosis.

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A Workflow for Patient-Individualized Virtual Angiogram Generation Based on CFD Simulation

Computational and Mathematical Methods in Medicine ◽

10.1155/2012/306765 ◽

2012 ◽

Vol 2012 ◽

pp. 1-24 ◽

Cited By ~ 14

Author(s):

Jürgen Endres ◽

Markus Kowarschik ◽

Thomas Redel ◽

Puneet Sharma ◽

Viorel Mihalef ◽

...

Keyword(s):

Fluid Dynamics ◽

Blood Flow ◽

Shear Stress ◽

Cfd Simulation ◽

Cerebral Aneurysms ◽

Patient Specific ◽

Hemodynamic Parameters ◽

Risk Of Rupture ◽

Computational Fluid Dynamics Cfd ◽

Subsequent Comparison

Increasing interest is drawn on hemodynamic parameters for classifying the risk of rupture as well as treatment planning of cerebral aneurysms. A proposed method to obtain quantities such as wall shear stress, pressure, and blood flow velocity is to numerically simulate the blood flow using computational fluid dynamics (CFD) methods. For the validation of those calculated quantities, virtually generated angiograms, based on the CFD results, are increasingly used for a subsequent comparison with real, acquired angiograms. For the generation of virtual angiograms, several patient-specific parameters have to be incorporated to obtain virtual angiograms which match the acquired angiograms as best as possible. For this purpose, a workflow is presented and demonstrated involving multiple phantom and patient cases.

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Investigation of two-way fluid-structure interaction of blood flow in a patient-specific left coronary artery

Bio-Medical Materials and Engineering ◽

10.3233/bme-201171 ◽

2021 ◽

pp. 1-18

Author(s):

Abdulgaphur Athani ◽

N.N.N. Ghazali ◽

Irfan Anjum Badruddin ◽

Sarfaraz Kamangar ◽

Ali E. Anqi ◽

...

Keyword(s):

Blood Flow ◽

Shear Stress ◽

Coronary Artery ◽

Wall Shear Stress ◽

Left Coronary Artery ◽

Fluid Structure Interaction ◽

Patient Specific ◽

Hemodynamic Parameters ◽

Fluid Structure ◽

Structure Interaction

BACKGROUND: The blood flow in the human artery has been a subject of sincere interest due to its prime importance linked with human health. The hemodynamic study has revealed an essential aspect of blood flow that eventually proved to be paramount to make a correct decision to treat patients suffering from cardiac disease. OBJECTIVE: The current study aims to elucidate the two-way fluid-structure interaction (FSI) analysis of the blood flow and the effect of stenosis on hemodynamic parameters. METHODS: A patient-specific 3D model of the left coronary artery was constructed based on computed tomography (CT) images. The blood is assumed to be incompressible, homogenous, and behaves as Non-Newtonian, while the artery is considered as a nonlinear elastic, anisotropic, and incompressible material. Pulsatile flow conditions were applied at the boundary. Two-way coupled FSI modeling approach was used between fluid and solid domain. The hemodynamic parameters such as the pressure, velocity streamline, and wall shear stress were analyzed in the fluid domain and the solid domain deformation. RESULTS: The simulated results reveal that pressure drop exists in the vicinity of stenosis and a recirculation region after the stenosis. It was noted that stenosis leads to high wall stress. The results also demonstrate an overestimation of wall shear stress and velocity in the rigid wall CFD model compared to the FSI model.

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Correlating aneurysm growth to hemodynamic parameters: the case of a patient-specific anterior communicating artery aneurysm

10.1117/12.595508 ◽

2005 ◽

Author(s):

Prem Venugopal ◽

Hui Chen ◽

Gary Duckwiler ◽

Richard Kemkers ◽

Pablo Villablanca ◽

...

Keyword(s):

Artery Aneurysm ◽

Patient Specific ◽

Anterior Communicating Artery ◽

Hemodynamic Parameters ◽

Anterior Communicating Artery Aneurysm ◽

Aneurysm Growth

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Risk of Rupture in AAA and Vulnerable Plaques: Patient Based FSI Simulation

ASME 2007 Summer Bioengineering Conference ◽

10.1115/sbc2007-176781 ◽

2007 ◽

Author(s):

Danny Bluestein ◽

Yared Alemu ◽

Peter Rissland ◽

Mikahil Britan ◽

Idit Avrahami ◽

...

Keyword(s):

Vulnerable Plaque ◽

Material Model ◽

Patient Specific ◽

Rupture Risk ◽

Fibrous Cap ◽

Wall Properties ◽

Aneurysm Wall ◽

Abdominal Aortic ◽

Risk Of Rupture ◽

Failure Location

Two separate fluid structure interaction (FSI) simulations were performed: a patient-specific Abdominal Aortic Aneurysm (AAA) geometry, and an idealized coronary vulnerable plaque (VP) geometry. VP FSI simulations were later performed in patient based geometries reconstructed from intravascular (IVUS) measurements. (AAA): The patient specific AAA FSI simulation was carried out with both isotropic and anisotropic wall properties. An orthotropic material model was used to describe wall properties, closely approximate experimental results [1]. Results show peak wall stresses are dependent on the geometry of the AAA and the region of highest stress corresponds to expected failure location. The ability to quantify stresses developing within the aneurysm wall based on FSI simulations will facilitate clinicians to reach informed decisions in determining rupture risk of AAA and the need for surgical intervention. (Vulnerable Plaque): To study the risk of rupture of a vulnerable plaque in an idealized coronary artery geometry, an FSI simulation was performed. This model of vulnerable plaque includes vessel wall with calcification spot embedded in the fibrous cap, and a lipid core. Identifying rupture risk, regions susceptible to failure and the contribution of the various components were studied. This work led to predicting the rupture risk in patient specific geometries. The results show the upstream side of vulnerable plaque fibrous cap has the highest stresses. The presence of the calcified spot is shown to enhance stresses within the fibrous cap, significantly contributing to its risk of rupture.

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Hemodynamic Metrics Correlate With Intracranial Aneurysm Rupture Status Better Than Morphologic Metrics

ASME 2010 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2010-19664 ◽

2010 ◽

Author(s):

Jianping Xiang ◽

Sabareesh K. Natarajan ◽

Markus Tremmel ◽

Ding Ma ◽

J. Mocco ◽

...

Keyword(s):

Prophylactic Treatment ◽

Aneurysm Rupture ◽

Patient Specific ◽

Hemodynamic Parameters ◽

Unruptured Aneurysms ◽

3D Angiography ◽

Unruptured Intracranial Aneurysms ◽

Complex Shapes ◽

Computational Fluid Dynamics Cfd ◽

Better Than

Given the considerable risk of treating unruptured intracranial aneurysms (IAs), as well as the known severe morbidity of aneurysm rupture, elucidating those aneurysms that require prophylactic treatment can be a quandary. Traditionally, decision-making to treat an unruptured aneurysm was largely based on the Size of the aneurysm, but recent studies have failed to show significant correlation of Size with IA rupture, and a large number of ruptured aneurysms are small in Size.[1] Consequently, shape-based morphologic metrics have been explored in current investigations, and complex shapes have been correlated with rupture.[1] With the advancement of 3D angiography, and computational fluid dynamics (CFD) technology, patient-specific hemodynamics analysis has become feasible. Intra-aneurysmal hemodynamic factors, including wall shear stress (WSS), impingement regions, and oscillatory shear index (OSI), have been proposed as indicators for IA rupture risk.[2, 3] No study has rigorously examined both morphology-based and hemodynamics-based parameters from a uniform cohort to compare their relative importance. Our aim, therefore, was to identify significant morphologic and hemodynamic parameters that correlate with an aneurysm’s rupture status and examine whether hemodynamic parameters can separate ruptured and unruptured aneurysms better than morphologic parameters.

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A longitudinal comparison of hemodynamics and intraluminal thrombus deposition in abdominal aortic aneurysms

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00461.2014 ◽

2014 ◽

Vol 307 (12) ◽

pp. H1786-H1795 ◽

Cited By ~ 44

Author(s):

Amirhossein Arzani ◽

Ga-Young Suh ◽

Ronald L. Dalman ◽

Shawn C. Shadden

Keyword(s):

Spin Echo ◽

Aortic Aneurysms ◽

Fast Spin Echo ◽

Patient Specific ◽

Black Blood ◽

Hemodynamic Parameters ◽

Dynamics Modeling ◽

Spatially Resolved ◽

Abdominal Aortic ◽

Risk Of Rupture

Abdominal aortic aneurysm (AAA) is often accompanied by in traluminal thrombus (ILT), which complicates AAA progression and risk of rupture. Patient-specific computational fluid dynamics modeling of 10 small human AAA was performed to investigate relations between hemodynamics and ILT progression. The patients were imaged using magnetic resonance twice in a 2- to 3-yr interval. Wall content data were obtained by a planar T1-weighted fast spin echo black-blood scan, which enabled quantification of thrombus thickness at midaneurysm location during baseline and followup. Computational simulations with patient-specific geometry and boundary conditions were performed to quantify the hemodynamic parameters of time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), and mean exposure time at baseline. Spatially resolved quantifications of the change in ILT thickness were compared with the different hemodynamic parameters. Regions of low OSI had the strongest correlation with ILT growth and demonstrated a statistically significant correlation coefficient. Prominent regions of high OSI (>0.4) and low TAWSS (<1 dyn/cm2) did not appear to coincide with locations of thrombus deposition.

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Estimation of wall properties and wall strength of aortic aneurysms using modern imaging techniques. One more step towards a patient-specific assessment of aneurysm rupture risk

Medical Hypotheses ◽

10.1016/j.mehy.2013.04.048 ◽

2013 ◽

Vol 81 (2) ◽

pp. 212-215 ◽

Cited By ~ 6

Author(s):

Nikolaos Kontopodis ◽

Efstratios Georgakarakos ◽

Eleni Metaxa ◽

Konstantinos Pagonidis ◽

Yannis Papaharilaou ◽

...

Keyword(s):

Imaging Techniques ◽

Aneurysm Rupture ◽

Aortic Aneurysms ◽

Patient Specific ◽

Rupture Risk ◽

Modern Imaging ◽

Wall Properties ◽

Wall Strength ◽

Specific Assessment

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Simulation of Blood Flow in Deformable Arteries Using Subject-Specific Geometry and Variable Vessel Wall Properties

ASME 2009 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2009-206183 ◽

2009 ◽

Cited By ~ 1

Author(s):

Guanglei Xiong ◽

C. Alberto Figueroa ◽

Nan Xiao ◽

Charles A. Taylor

Keyword(s):

Blood Flow ◽

Geometric Model ◽

Cerebral Aneurysms ◽

Patient Specific ◽

Wall Properties ◽

Subject Specific ◽

Vessel Wall Properties ◽

Specific Geometry ◽

Variable Wall ◽

Dynamics Simulations

Previous efforts to simulate blood flow in patient-specific models either assumed rigid vessel walls or deformable walls with constant mechanical property [1]. We have developed a new workflow to enable blood flow and vessel dynamics simulations using subject-specific geometry and variable wall properties. The geometric model construction is based on 3D segmentation and geometric processing which greatly reduce human labor and increase the objectivity of the model. Variable wall properties are assigned to the model based on combining centerline-based and surface-based methods. This new approach was successfully applied to simulate blood flow and wall dynamics in models with abdominal, thoracic, and cerebral aneurysms.

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