Estimation of Atherosclerotic Plaque Material Properties: A Mixed Method of Strain Imaging and Inverse Finite Element Analysis

2013 ◽  
Author(s):  
A. C. Akyildiz ◽  
H. H. G. Hansen ◽  
C. L. de Korte ◽  
L. Speelman ◽  
J. Wentzel ◽  
...  
Keyword(s):  
Material Properties ◽  
Prediction Models ◽  
Plaque Rupture ◽  
Thrombus Formation ◽  
Large Strains ◽  
Reliable Prediction ◽  
Element Analysis ◽  
Biomechanical Models ◽  
Wide Range ◽  
Inverse Finite Element Analysis

Atherosclerosis is a cardiovascular disease characterized by plaque formation in the vessel wall. Plaque rupture initiates thrombus formation and may lead to myocardial infarction, stroke and eventually, to sudden death [1]. A plaque ruptures when the mechanical stress in the plaque exceeds its strength. Thus, biomechanical models have a great potential to predict plaque rupture. For reliable prediction models, correct material properties of plaque components at large strains are prerequisite. However, the data available in literature are limited and show a wide range.

A REVIEW OF FINITE ELEMENT APPLICATIONS IN ORAL AND MAXILLOFACIAL BIOMECHANICS

2018 ◽  
Vol 18 (02) ◽  
pp. 1830002 ◽  
Author(s):  
SUZAN CANSEL DOGRU ◽  
EROL CANSIZ ◽  
YUNUS ZIYA ARSLAN
Keyword(s):  
Finite Element ◽  
Boundary Conditions ◽  
Material Properties ◽  
Dental Materials ◽  
Numerical Approach ◽  
Patient Specific ◽  
Element Analysis ◽  
Biomechanical Models ◽  
Dental Instruments ◽  
Wide Range

Finite element method (FEM) is preferred to carry out mechanical analyses for many complex biomechanical structures. For most of the biomechanical models such as oral and maxillofacial structures or patient-specific dental instruments, including nonlinearities, complicated geometries, complex material properties, or loading/boundary conditions, it is not possible to accomplish an analytical solution. The FEM is the most widely used numerical approach for such cases and found a wide range of application fields for investigating the biomechanical characteristics of oral and maxillofacial structures that are exposed to external forces or torques. The numerical results such as stress or strain distributions obtained from finite element analysis (FEA) enable dental researchers to evaluate the bone tissues subjected to the implant or prosthesis fixation from the viewpoint of (i) mechanical strength, (ii) material properties, (iii) geometry and dimensions, (iv) structural properties, (v) loading or boundary conditions, and (vi) quantity of implants or prostheses. This review paper evaluates the process of the FEA of the oral and maxillofacial structures step by step as followings: (i) a general perspective on the techniques for creating oral and maxillofacial models, (ii) definitions of material properties assigned to oral and maxillofacial tissues and related dental materials, (iii) definitions of contact types between tissue and dental instruments, (iv) details on loading and boundary conditions, and (v) meshing process.

scholarly journals Estimating the material properties of heel pad sub-layers using inverse Finite Element Analysis

2017 ◽  
Vol 40 ◽  
pp. 11-19 ◽  
Author(s):  
Nafiseh Ahanchian ◽  
Christopher J. Nester ◽  
David Howard ◽  
Lei Ren ◽  
Daniel Parker
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Material Properties ◽  
Element Analysis ◽  
Heel Pad ◽  
Inverse Finite Element Analysis

Biomechanical Modeling of Atherosclerotic Lesions in ApoE Deficient Mice

2009 ◽  
Author(s):  
Yuliya Vengrenyuk ◽  
Theodore J. Kaplan ◽  
Luis Cardoso ◽  
Gwendalyn J. Randolph ◽  
Sheldon Weinbaum
Keyword(s):  
Plaque Rupture ◽  
Thrombus Formation ◽  
Western World ◽  
Histopathological Analysis ◽  
Anatomic Site ◽  
Aortic Sinus ◽  
Element Analysis ◽  
Atherosclerotic Lesions ◽  
Genetically Engineered Mice ◽  
Deficient Mice

Cardiovascular disease remains the principal killer in the western world despite major advances in treatment of its patients [1]. It is generally accepted that sudden rupture of vulnerable plaque followed by thrombus formation underlies most cases of myocardial infarction and is responsible for more than a half of 500,000 coronary heart disease deaths every year. Although histopathological analysis of postmortem specimens have provided important data on histological features of ruptured human plaques, there is an urgent need for good representative animal models of plaque rupture. Over the last decade and a half, genetically engineered mice have been widely used to study the pathogenesis and potential treatment of atherosclerotic lesions, as well as genetic, hormonal and environmental influences on development of atherosclerosis. Though many of the features of plaque development and progression that occur in human plaques are similarly observed in murine plaques, these mouse models have long been regarded as poor models to study plaque rupture because the aortic sinus lesions seldom show any signs of fibrous cap disruption. Several recent studies reported potentially unstable atherosclerotic lesions in older apoE-deficient mice in another anatomic site, the proximal part of the brachiocephalic artery (BCA) [2, 3]. The unusual stability of aortic lesions compared to the BCA lesions in ApoE knockout mice is an unexplained paradox in developing a mouse model of plaque rupture. In this paper, we use histology based finite element analysis to evaluate peak circumferential stresses in aortic and BCA lesions from high fat fed ApoE KO mice.

Local Anisotropic Mechanical Behavior of Human Carotid Atherosclerotic Plaques: Characterization Using Indentation Test and Inverse Finite Element Analysis

2013 ◽  
Author(s):  
Chen-Ket Chai ◽  
Ali C. Akyildiz ◽  
Lambert Speelman ◽  
Frank J. H. Gijsen ◽  
Cees W. J. Oomens ◽  
...  
Keyword(s):  
Arterial Wall ◽  
Thrombus Formation ◽  
Indentation Test ◽  
Inflammatory Cells ◽  
Blood Stream ◽  
Intraplaque Hemorrhage ◽  
Vulnerable Atherosclerotic Plaque ◽  
Element Analysis ◽  
Fibrous Cap ◽  
Inverse Finite Element Analysis

Atherosclerosis is a disorder of the arterial wall. The vessel wall is invaded by lipids and inflammatory cells which can lead to thickening of the arterial wall and eventually to formation of a vulnerable atherosclerotic plaque. Such a vulnerable plaque consists of intraplaque hemorrhage, inflammatory cells, a lipid rich necrotic core (LRNC) and a thin fibrous cap separating the thrombogenic LRNC from the blood stream. The thin fibrous cap is prone to rupture, which can cause thrombus formation and subsequent embolization of thrombus into distal vessels or acute occlusion. This is the major cause of stroke and myocardial infarction.

QUANTIFICATION OF IN VIVO MITRAL VALVE MATERIAL PROPERTIES USING INVERSE FINITE ELEMENT ANALYSIS

2008 ◽  
Vol 41 ◽  
pp. S119
Author(s):  
Gaurav Krishnamurthy ◽  
Daniel B. Ennis ◽  
Akinobu Itoh ◽  
Wolfgang Bothe ◽  
Julia Swanson ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Mitral Valve ◽  
Material Properties ◽  
Element Analysis ◽  
Inverse Finite Element Analysis

Quantification of In Vivo Stresses in the Ovine Anterior Mitral Valve Leaflet

2008 ◽  
Author(s):  
Gaurav Krishnamurthy ◽  
Akinobu Itoh ◽  
Wolfgang Bothe ◽  
Daniel B. Ennis ◽  
Julia C. Swanson ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Mitral Valve ◽  
Material Properties ◽  
Element Analysis ◽  
Mitral Valve Leaflet ◽  
Mitral Valves ◽  
Mitral Repair ◽  
Inverse Finite Element Analysis

Mitral valve (MV) disease affects millions worldwide. An important goal of present-day heart valve research is to create bioengineered tissue valves to replace diseased mitral valves, if it is judged that mitral repair will not be durable. The design of such valves will pivot on understanding the stresses acting in the native MV leaflets to design a bioprosthesis which will withstand these stresses. In order to quantify such stresses in vivo, we utilized radiopaque marker technology and performed an “inverse” finite element analysis of the resulting 4-D data to determine the material properties of the anterior MV leaflet in the beating ovine heart. We then used these material properties in a “forward” finite element analysis to estimate the stresses in the native anterior MV leaflet.

scholarly journals A Three-Dimensional Inverse Finite Element Analysis of the Heel Pad

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Snehal Chokhandre ◽  
Jason P. Halloran ◽  
Antonie J. van den Bogert ◽  
Ahmet Erdemir
Keyword(s):  
Experimental Data ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Material Properties ◽  
Three Dimensional ◽  
Element Analysis ◽  
Heel Pad ◽  
Tool Force ◽  
Specific Material ◽  
Inverse Finite Element Analysis

Quantification of plantar tissue behavior of the heel pad is essential in developing computational models for predictive analysis of preventive treatment options such as footwear for patients with diabetes. Simulation based studies in the past have generally adopted heel pad properties from the literature, in return using heel-specific geometry with material properties of a different heel. In exceptional cases, patient-specific material characterization was performed with simplified two-dimensional models, without further evaluation of a heel-specific response under different loading conditions. The aim of this study was to conduct an inverse finite element analysis of the heel in order to calculate heel-specific material properties in situ. Multidimensional experimental data available from a previous cadaver study by Erdemir et al. (“An Elaborate Data Set Characterizing the Mechanical Response of the Foot,” ASME J. Biomech. Eng., 131(9), pp. 094502) was used for model development, optimization, and evaluation of material properties. A specimen-specific three-dimensional finite element representation was developed. Heel pad material properties were determined using inverse finite element analysis by fitting the model behavior to the experimental data. Compression dominant loading, applied using a spherical indenter, was used for optimization of the material properties. The optimized material properties were evaluated through simulations representative of a combined loading scenario (compression and anterior-posterior shear) with a spherical indenter and also of a compression dominant loading applied using an elevated platform. Optimized heel pad material coefficients were 0.001084 MPa (μ), 9.780 (α) (with an effective Poisson’s ratio (ν) of 0.475), for a first-order nearly incompressible Ogden material model. The model predicted structural response of the heel pad was in good agreement for both the optimization (<1.05% maximum tool force, 0.9% maximum tool displacement) and validation cases (6.5% maximum tool force, 15% maximum tool displacement). The inverse analysis successfully predicted the material properties for the given specimen-specific heel pad using the experimental data for the specimen. The modeling framework and results can be used for accurate predictions of the three-dimensional interaction of the heel pad with its surroundings.

scholarly journals Material properties of the ovine mitral valve anterior leaflet in vivo from inverse finite element analysis

2008 ◽  
Vol 295 (3) ◽  
pp. H1141-H1149 ◽  
Author(s):  
Gaurav Krishnamurthy ◽  
Daniel B. Ennis ◽  
Akinobu Itoh ◽  
Wolfgang Bothe ◽  
Julia C. Swanson ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Mitral Valve ◽  
Material Properties ◽  
Element Model ◽  
Left Ventricular ◽  
Element Analysis ◽  
Inverse Finite Element Analysis

We measured leaflet displacements and used inverse finite-element analysis to define, for the first time, the material properties of mitral valve (MV) leaflets in vivo. Sixteen miniature radiopaque markers were sewn to the MV annulus, 16 to the anterior MV leaflet, and 1 on each papillary muscle tip in 17 sheep. Four-dimensional coordinates were obtained from biplane videofluoroscopic marker images (60 frames/s) during three complete cardiac cycles. A finite-element model of the anterior MV leaflet was developed using marker coordinates at the end of isovolumic relaxation (IVR; when the pressure difference across the valve is ∼0), as the minimum stress reference state. Leaflet displacements were simulated during IVR using measured left ventricular and atrial pressures. The leaflet shear modulus ( Gcirc-rad) and elastic moduli in both the commisure-commisure ( Ecirc) and radial ( Erad) directions were obtained using the method of feasible directions to minimize the difference between simulated and measured displacements. Group mean (±SD) values (17 animals, 3 heartbeats each, i.e., 51 cardiac cycles) were as follows: Gcirc-rad= 121 ± 22 N/mm2, Ecirc= 43 ± 18 N/mm2, and Erad= 11 ± 3 N/mm2( Ecirc> Erad, P < 0.01). These values, much greater than those previously reported from in vitro studies, may result from activated neurally controlled contractile tissue within the leaflet that is inactive in excised tissues. This could have important implications, not only to our understanding of mitral valve physiology in the beating heart but for providing additional information to aid the development of more durable tissue-engineered bioprosthetic valves.

Oxidative Stress and Atherosclerosis: Its Relationship to Growth Factors, Thrombus Formation and Therapeutic Approaches

1999 ◽  
Vol 82 (S 01) ◽  
pp. 32-37 ◽  
Author(s):  
Karlheinz Peter ◽  
Wolfgang Kübler ◽  
Johannes Ruef ◽  
Thomas K. Nordt ◽  
Marschall S. Runge ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Growth Factors ◽  
Vessel Wall ◽  
Inflammatory Responses ◽  
Plaque Rupture ◽  
Thrombus Formation ◽  
Vascular Lesion ◽  
Coagulation System ◽  
Therapeutic Approaches ◽  
Causative Relationship

SummaryThe initiating event of atherogenesis is thought to be an injury to the vessel wall resulting in endothelial dysfunction. This is followed by key features of atherosclerotic plaque formation such as inflammatory responses, cell proliferation and remodeling of the vasculature, finally leading to vascular lesion formation, plaque rupture, thrombosis and tissue infarction. A causative relationship exists between these events and oxidative stress in the vessel wall. Besides leukocytes, vascular cells are a potent source of oxygen-derived free radicals. Oxidants exert mitogenic effects that are partially mediated through generation of growth factors. Mitogens, on the other hand, are potent stimulators of oxidant generation, indicating a putative self-perpetuating mechanism of atherogenesis. Oxidants influence the balance of the coagulation system towards platelet aggregation and thrombus formation. Therapeutic approaches by means of antioxidants are promising in both experimental and clinical designs. However, additional clinical trials are necessary to assess the role of antioxidants in cardiovascular disease.

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