scholarly journals Characterization of Exercise-Induced Myocardium Growth Using Finite Element Modeling and Bayesian Optimization

2021 ◽  
Vol 12 ◽  
Author(s):  
Yiling Fan ◽  
Jaume Coll-Font ◽  
Maaike van den Boomen ◽  
Joan H. Kim ◽  
Shi Chen ◽  
...  
Keyword(s):  
Finite Element ◽  
Growth Parameters ◽  
Constitutive Models ◽  
Left Ventricular ◽  
Bayesian Optimization ◽  
Fe Model ◽  
Imaging Data ◽  
Growth And Remodeling ◽  
Organ Level ◽  
Exercise Induced

Cardiomyocyte growth can occur in both physiological (exercised-induced) and pathological (e.g., volume overload and pressure overload) conditions leading to left ventricular (LV) hypertrophy. Studies using animal models and histology have demonstrated the growth and remodeling process at the organ level and tissue–cellular level, respectively. However, the driving factors of growth and the mechanistic link between organ, tissue, and cellular growth remains poorly understood. Computational models have the potential to bridge this gap by using constitutive models that describe the growth and remodeling process of the myocardium coupled with finite element (FE) analysis to model the biomechanics of the heart at the organ level. Using subject-specific imaging data of the LV geometry at two different time points, an FE model can be created with the inverse method to characterize the growth parameters of each subject. In this study, we developed a framework that takes in vivo cardiac magnetic resonance (CMR) imaging data of exercised porcine model and uses FE and Bayesian optimization to characterize myocardium growth in the transverse and longitudinal directions. The efficacy of this framework was demonstrated by successfully predicting growth parameters of 18 synthetic LV targeted masks which were generated from three LV porcine geometries. The framework was further used to characterize growth parameters in 4 swine subjects that had been exercised. The study suggested that exercise-induced growth in swine is prone to longitudinal cardiomyocyte growth (58.0 ± 19.6% after 6 weeks and 79.3 ± 15.6% after 12 weeks) compared to transverse growth (4.0 ± 8.0% after 6 weeks and 7.8 ± 9.4% after 12 weeks). This framework can be used to characterize myocardial growth in different phenotypes of LV hypertrophy and can be incorporated with other growth constitutive models to study different hypothetical growth mechanisms.

Mechanism of Slow Crack Growth in Polyethylene: A Finite Element Approach

2015 ◽  
Author(s):  
Xiangpeng Luo ◽  
Jianfeng Shi ◽  
Jinyang Zheng
Keyword(s):  
Finite Element ◽  
Crack Growth ◽  
Failure Time ◽  
Bulk Material ◽  
Slow Crack Growth ◽  
Damage Model ◽  
Constitutive Models ◽  
Fe Model ◽  
Notch Angle ◽  
Craze Zone

Slow crack growth (SCG) is a common failure mode in underground polyethylene (PE) piping which was designed for 50-year services. It had been revealed by experiments that the SCG process is caused by continuous propagation of the craze zone at the crack tip through the bulk material. However, the mechanism of SCG failure has not been understood clearly. The eXtended Finite Element Method (XFEM) is found to be an effective tool for locally non-smooth features (voids, cracks, etc.) in solid or fluid mechanics solutions. In this paper the time-dependent property of PE was considered, a viscoelastic constitutive model was used for the bulk material. To represent the material deterioration during SCG, a damage model was developed for the craze zone. Combined with the XFEM, the process of the Pennsylvania Notched Test (PENT), which had been widely applied for characterizing resistance of SCG for PE pipes or resins, was analyzed based on the proposed finite element (FE) model containing the two constitutive models. The numerical results were then compared with the experimental data in literatures. It showed that the failure time and final notch angle were in agreement with the experimental observations. Based on the verified FE model, strain distributions along the boundary of the crack were studied and the shortcomings of this model were discussed.

Integration of Microstructural Architecture of the Mitral Valve Into an Anatomically Accurate Finite Element Mesh

2012 ◽  
Author(s):  
Rouzbeh Amini ◽  
Inge van Loosdregt ◽  
Kevin Koomalsingh ◽  
Robert C. Gorman ◽  
Joseph H. Gorman ◽  
...  
Keyword(s):  
Finite Element ◽  
Mitral Valve ◽  
Constitutive Models ◽  
Geometrical Model ◽  
Finite Element Models ◽  
Element Mesh ◽  
Microstructural Alterations ◽  
Organ Level ◽  
Collagenous Tissues

Although mitral valve (MV) repair initially restores normal leaflets coaptation and stops MV regurgitation, in long term it can also dramatically change the leaflet geometry and stress distribution that may be in part responsible for limited repair durability. As shown for other collagenous tissues, such changes in geometry and loading reorganize the fiber architecture. In addition, MV interstitial cells respond to the altered stress by undergoing alterations in biosynthetic function, which would affect the load-bearing capabilities of MV and its long-term durability. Thus, investigating the repair-induced MV stress and the concomitant microstructural alterations is a key step in assessing the repaired valve durability. Finite element models have been widely used for stress analysis of the mitral valve [1–3]. Most of these models, however, have employed only basic constitutive models and utilized simplified valve geometry. Above all, they have ignored the complex microstructure of the MV, which is the critical physical link between organ level stresses and cellular function. Thus, in this work we developed an initial method to develop an accurate geometrical model of the ovine MV and map the fiber structure for the purposes of developing high fidelity computational meshes of the MV.

A Novel Micro-CT Based Anatomically Accurate Finite Element Model for Simulation-Aided Assessment of Mitral Valve Repairs

2013 ◽  
Author(s):  
Chung-Hao Lee ◽  
Robert C. Gorman ◽  
Joseph H. Gorman ◽  
Rouzbeh Aimini ◽  
Michael S. Sacks
Keyword(s):  
Finite Element ◽  
Mitral Valve ◽  
Mitral Regurgitation ◽  
Constitutive Models ◽  
Element Model ◽  
Tissue Level ◽  
Cellular Level ◽  
Fe Model ◽  
Mitral Valves ◽  
Mechanical Responses

Many surgeons have come to view mitral valve (MV) repair as the treatment of choice in patients with mitral regurgitation (MR) [1]. According to recent long-term studies, the recurrence of significant MR after repair may be much higher than previously believed, particularly in patients with (ischemic mitral regurgitation) IMR [2]. We hypothesize that the restoration of homeostatic normal MV leaflet tissue stress in IMR repair techniques ultimately leads to improved repair durability. Therefore, the objective of this study is to develop a novel micro-anatomically accurate 3D finite element (FE) model that incorporates detailed collagen fiber architecture, accurate constitutive models, and micro-anatomically realistic valvular geometry to investigate the functional mitral valve and to aid in the assessment of the mitral valve repairs, especially the linking between the interstitial cellular deformations at the cellular level, the mechanobiological behaviors at the tissue level and the organ level mechanical responses as normal and repaired mitral valves maintaining their homeostatic state.

scholarly journals Regional Left Ventricular Myocardial Contractility and Stress in a Finite Element Model of Posterobasal Myocardial Infarction

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Jonathan F. Wenk ◽  
Kay Sun ◽  
Zhihong Zhang ◽  
Mehrdad Soleimani ◽  
Liang Ge ◽  
...  
Keyword(s):  
Finite Element ◽  
Myocardial Contractility ◽  
Left Ventricular ◽  
Border Zone ◽  
Left Ventricular Aneurysm ◽  
Fe Model ◽  
Ventricular Aneurysm ◽  
Computationally Efficient ◽  
Lv Volumes ◽  
Formal Optimization

Recently, a noninvasive method for determining regional myocardial contractility, using an animal-specific finite element (FE) model-based optimization, was developed to study a sheep with anteroapical infarction (Sun et al., 2009, “A Computationally Efficient Formal Optimization of Regional Myocardial Contractility in a Sheep With Left Ventricular Aneurysm,” ASME J. Biomech. Eng., 131(11), p. 111001). Using the methodology developed in the previous study (Sun et al., 2009, “A Computationally Efficient Formal Optimization of Regional Myocardial Contractility in a Sheep With Left Ventricular Aneurysm,” ASME J. Biomech. Eng., 131(11), p. 111001), which incorporates tagged magnetic resonance images, three-dimensional myocardial strains, left ventricular (LV) volumes, and LV cardiac catheterization pressures, the regional myocardial contractility and stress distribution of a sheep with posterobasal infarction were investigated. Active material parameters in the noninfarcted border zone (BZ) myocardium adjacent to the infarct (Tmax_B), in the myocardium remote from the infarct (Tmax_R), and in the infarct (Tmax_I) were estimated by minimizing the errors between FE model-predicted and experimentally measured systolic strains and LV volumes using the previously developed optimization scheme. The optimized Tmax_B was found to be significantly depressed relative to Tmax_R, while Tmax_I was found to be zero. The myofiber stress in the BZ was found to be elevated, relative to the remote region. This could cause further damage to the contracting myocytes, leading to heart failure.

scholarly journals Organ-level validation of a cross-bridge cycling descriptor in a left ventricular finite element model: effects of ventricular loading on myocardial strains

2017 ◽  
Vol 5 (21) ◽  
pp. e13392 ◽  
Author(s):  
Sheikh Mohammad Shavik ◽  
Samuel T. Wall ◽  
Joakim Sundnes ◽  
Daniel Burkhoff ◽  
Lik Chuan Lee
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Element Model ◽  
Left Ventricular ◽  
Cross Bridge ◽  
Organ Level

A High Fidelity, Micro-Structural and Anatomically Accurate 3D Finite Element Model for Functioning Heart Mitral Valve

2013 ◽  
Author(s):  
Chung-Hao Lee ◽  
Pim J. A. Oomen ◽  
Jean Pierre Rabbah ◽  
Neela Saikrishnan ◽  
Ajit Yoganathan ◽  
...  
Keyword(s):  
Finite Element ◽  
Mitral Valve ◽  
Mitral Regurgitation ◽  
Constitutive Models ◽  
Element Model ◽  
Suture Line ◽  
High Fidelity ◽  
Fe Model ◽  
3D Finite Element ◽  
Mechanical Responses

Many surgeons have come to view mitral valve (MV) repair as the treatment of choice in patients with mitral regurgitation (MR) [1]. However, recent long-term studies have indicated that the recurrence of significant MR after repair may be much higher than previously believed, particularly in patients with (ischemic mitral regurgitation) IMR [2]. Since a significant number of these failures result from chordal, leaflet and suture line disruption, it has been suggested that excessive tissue stress and the resulting strain-induced tissue damage are important etiologic factors. We thus hypothesize that the restoration of homeostatic normal MV leaflet tissue stress levels in IMR repair techniques ultimately leads to improved repair durability through restoration of normal MV responses. Therefore, the objective of this study is to develop a novel high-fidelity and micro-anatomically accurate 3D finite element (FE) model that incorporates detailed collagen fiber architecture, realistic constitutive models, and micro-anatomically accurate valvular geometry to connect the cellular function of the MV tissues with the organ level mechanical responses, and to aid in the design of MV repair procedures.

Finite Element Implementation of a Structural Constitutive Model for Heart Valve Biomaterials

2002 ◽  
Author(s):  
Wei Sun ◽  
Michael S. Sacks ◽  
Michael Scott
Keyword(s):  
Finite Element ◽  
Constitutive Model ◽  
Heart Valve ◽  
Mechanical Response ◽  
Constitutive Models ◽  
Fe Model ◽  
Orientation Data ◽  
Composition And Structure ◽  
Anisotropic Mechanical Properties ◽  
Analytical Result

Accurate computational modeling of the non-linear, anisotropic mechanical properties of heart valve biomaterials remains an important and challenging area. Unlike phenomenological models, structurally based constitutive models attempt to exploit the tissue composition and structure to avoid ambiguities in material characterization, and offer insight into the function, structure, and mechanics of tissue components. Current finite element (FE) simulations of heart valve biomaterials do not simulate the complete anisotropic mechanical response, limiting simulation realism. In this study, we implemented structural constitutive model developed in our lab that incorporates SALS-derived fiber orientation data. The FE model was validated by both analytical result and experimental data.

scholarly journals Finite Element Modeling and Physical Property Estimation of Rheological Food Objects

2012 ◽  
Vol 1 (1) ◽  
pp. 48 ◽  
Author(s):  
Zhongkui Wang ◽  
Shinichi Hirai
Keyword(s):  
Finite Element ◽  
Parameter Estimation ◽  
Estimation Method ◽  
Constitutive Models ◽  
Residual Deformation ◽  
Physical Property ◽  
Element Model ◽  
Fe Model ◽  
Step Method ◽  
Rheological Behaviors

<p>The purpose of this study is to accurately simulate the rheological behaviors of food objects undergoing a loading-unloading operation using finite element (FE) model. Due to the presence of residual deformation, it is difficult to model rheological behaviors. Especially, it is hard to accurately reproduce both rheological force and residual deformation simultaneously. In this study, objects made of food materials were tested. Force and deformation measurements were recorded for parameter estimation. Constitutive models were investigated for describing rheological behaviors. A parallel five-element model including two dual-moduli viscous elements was proposed to accurately predict both rheological force and residual deformation simultaneously. 2D/3D FE model was formulated for simulating rheological behaviors. To estimate the parameters, an effective four-step method was established based on nonlinear optimization which aimed at minimizing the differences of forces and deformation between simulation and experiments. The proposed FE model and parameter estimation method were validated in both 2D and 3D cases and good agreements were achieved in both rheological forces and deformation between numerically simulated and experimentally measured data.</p>

A Non-Matching Nodes Interface Model with Radial Interpolation Function for Simulating 2D Soil–Structure Interface Behaviors

2020 ◽  
Vol 18 (01) ◽  
pp. 2050023
Author(s):  
Jin Gong ◽  
Degao Zou ◽  
Xianjing Kong ◽  
Yongqian Qu ◽  
Yang Zhou
Keyword(s):  
Finite Element ◽  
Meshless Method ◽  
Soil Structure ◽  
Constitutive Models ◽  
Fe Model ◽  
Interpolation Function ◽  
Interface Elements ◽  
Background Mesh ◽  
High Flexibility ◽  
Gauss Points

In this paper, the meshless method is extended to simulate the interaction between soil and structure through 2D finite element (FE) model. The background mesh line shared by each surface of interface is introduced for Gauss points’ generation and interpolation. Thus, instead of a series of interface elements, the whole soil–structure interface can be presented by an arbitrary number of nodes with flexible distribution on the contacting surfaces. The radial basis function (RBF) is introduced as the interpolation function to obtain the displacement of each Gauss points by surrounding the nodes along the surfaces. The research of shape parameters and the rate of convergence are also conducted. With non-matching nodes interface, the soil and structure zone can be modeled independently and connected with the proposed non-matching nodes interface flexibly and effectively. Furthermore, the proposed method can easily enable cross-scale modeling, which has high utility for enabling refined analysis without excessively increasing the computational costs. In addition, under the standard finite element framework, nonlinear constitutive models can be employed to capture the complex behaviors at the interface. Several simulations are presented to demonstrate the high flexibility, extensive applicability and precision of the proposed non-matching nodes interface based on meshless method.

A Multi-Zone Finite Element Model for Radiofrequency Ablation of an Infarcted Cardiac Tissue

2007 ◽  
Author(s):  
Fan Zhou ◽  
Ying Sun ◽  
Jacques Beaumont
Keyword(s):  
Finite Element ◽  
Cardiac Arrhythmia ◽  
Element Model ◽  
Severe Bleeding ◽  
Minimal Amount ◽  
Fe Model ◽  
Rf Ablation ◽  
Imaging Data ◽  
Conduction Model ◽  
Thermo Electric

A large number of modern day medical interventions rely on RF ablation. It has become the treatment of choice for many types of cardiac arrhythmia to prevent the reentrant circuits [1]. However, excessive heating during RF ablation up to 100°C can cause microexplosions and severe bleeding [2]. Optimizing parameters for RF ablation in order to produce small lesions with a minimal amount of damage and bleeding constitutes a major challenge. Utilizing a thermo-electric conduction model, we address this problem for the treatment of cardiac arrhythmia. Our objective is to provide means by which non-invasive cardiac imaging data can be used to determine optimal parameters of RF ablation. A three-dimensional (3-D) finite element (FE) model that includes healthy, infarcted, and slow conducting tissues is developed. The temperature dependent thermal and electrical conductivities are considered for different tissue types.

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