scholarly journals Effects of Residual Stress, Axial Stretch, and Circumferential Shrinkage on Coronary Plaque Stress and Strain Calculations: A Modeling Study Using IVUS-Based Near-Idealized Geometries

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Liang Wang ◽  
Jian Zhu ◽  
Habib Samady ◽  
David Monoly ◽  
Jie Zheng ◽  
...  
Keyword(s):  
Residual Stress ◽  
Coronary Plaque ◽  
Model Construction ◽  
Patient Specific ◽  
Stress And Strain ◽  
Stress Strain ◽  
Axial Stretch ◽  
Stress Increase ◽  
Specific Material

Accurate stress and strain calculations are important for plaque progression and vulnerability assessment. Models based on in vivo data often need to form geometries with zero-stress/strain conditions. The goal of this paper is to use IVUS-based near-idealized geometries and introduce a three-step model construction process to include residual stress, axial shrinkage, and circumferential shrinkage and investigate their impacts on stress and strain calculations. In Vivo intravascular ultrasound (IVUS) data of human coronary were acquired for model construction. In Vivo IVUS movie data were acquired and used to determine patient-specific material parameter values. A three-step modeling procedure was used to make our model: (a) wrap the zero-stress vessel sector to obtain the residual stress; (b) stretch the vessel axially to its length in vivo; and (c) pressurize the vessel to recover its in vivo geometry. Eight models were constructed for our investigation. Wrapping led to reduced lumen and cap stress and increased out boundary stress. The model with axial stretch, circumferential shrink, but no wrapping overestimated lumen and cap stress by 182% and 448%, respectively. The model with wrapping, circumferential shrink, but no axial stretch predicted average lumen stress and cap stress as 0.76 kPa and −15 kPa. The same model with 10% axial stretch had 42.53 kPa lumen stress and 29.0 kPa cap stress, respectively. Skipping circumferential shrinkage leads to overexpansion of the vessel and incorrect stress/strain calculations. Vessel stiffness increase (100%) leads to 75% lumen stress increase and 102% cap stress increase.

Abstract 383: Patient-Specific Coronary Models Combining Intravascular Ultrasound and Optical Coherence Tomography Lead to More Accurate Plaque Cap Thickness and Stress/Strain Quantifications

2017 ◽  
Vol 37 (suppl_1) ◽  
Author(s):  
Xiaoya Guo ◽  
David Monoly ◽  
Chun Yang ◽  
Habib Samady ◽  
Jie Zheng ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Intravascular Ultrasound ◽  
Coronary Plaque ◽  
Patient Specific ◽  
Data Sets ◽  
Optical Coherence ◽  
Stress Strain ◽  
Data Set ◽  
The Impact

Accurate cap thickness and stress/strain quantifications are of fundamental importance for vulnerable plaque research. An innovative modeling approach combining intravascular ultrasound (IVUS) and optical coherence tomography (OCT) is introduced for more accurate patient-specific coronary morphology and stress/strain calculations. In vivo IVUS and OCT coronary plaque data were acquired from two patients with informed consent obtained. IVUS and OCT images were segmented, co-registered, and merged to form the IVUS+OCT data set, with OCT providing accurate cap thickness. Biplane angiography provided 3D vessel curvature. Due to IVUS resolution (150 μm), original virtual histology (VH) IVUS data often had lipid core exposed to lumen since it sets cap thickness as zero when cap thickness <150 μm. VH-IVUS data were processed with minimum cap thickness set as 50 and 180 μm to generate IVUS50 and IVUS180 data sets for modeling use. 3D fluid-structure interaction models based on IVUS+OCT, IVUS50 and IVUS180 data sets were constructed to investigate the impact of OCT cap thickness improvement on stress/strain calculations. Figure 1 is a brief summary of results from 27 slices with cap covering lipid cores from 2 patients. Mean cap thickness (unit: mm) from Patient 1 was 0.353 (OCT), 0.201 (IVUS50), and 0.329 (IVUS180), respectively. Patient 2 mean cap thickness was 0.320 (OCT), 0.224 (IVUS50), and 0.285 (IVUS180). IVUS50 underestimated cap thickness (27 slices) by 34.5%, compared to OCT cap values. IVUS50 overestimated mean cap stress (27 slices) by 45.8%, compared to OCT cap stress (96.4 vs. 66.1 kPa). IVUS50 maximum cap stress was 59.2% higher than that from IVUS+OCT model (564.2 vs. 354.5 kPa). Differences between IVUS and IVUS+OCT models for mean cap strain and flow shear stress were modest (cap strain: <12%; FSS <2%). Conclusion: IVUS+OCT data and models could provide more accurate cap thickness and stress/strain calculations which will serve as basis for plaque research.

scholarly journals Infarcted Left Ventricles Have Stiffer Material Properties and Lower Stiffness Variation: Three-Dimensional Echo-Based Modeling to Quantify In Vivo Ventricle Material Properties

2015 ◽  
Vol 137 (8) ◽  
Author(s):  
Longling Fan ◽  
Jing Yao ◽  
Chun Yang ◽  
Dalin Tang ◽  
Di Xu
Keyword(s):  
Wall Thickness ◽  
Material Properties ◽  
Strain Curve ◽  
Stress And Strain ◽  
Stress Strain ◽  
Material Stiffness ◽  
The Mean ◽  
Lv Volume ◽  
Parameter Values

Methods to quantify ventricle material properties noninvasively using in vivo data are of great important in clinical applications. An ultrasound echo-based computational modeling approach was proposed to quantify left ventricle (LV) material properties, curvature, and stress/strain conditions and find differences between normal LV and LV with infarct. Echo image data were acquired from five patients with myocardial infarction (I-Group) and five healthy volunteers as control (H-Group). Finite element models were constructed to obtain ventricle stress and strain conditions. Material stiffening and softening were used to model ventricle active contraction and relaxation. Systolic and diastolic material parameter values were obtained by adjusting the models to match echo volume data. Young's modulus (YM) value was obtained for each material stress–strain curve for easy comparison. LV wall thickness, circumferential and longitudinal curvatures (C- and L-curvature), material parameter values, and stress/strain values were recorded for analysis. Using the mean value of H-Group as the base value, at end-diastole, I-Group mean YM value for the fiber direction stress–strain curve was 54% stiffer than that of H-Group (136.24 kPa versus 88.68 kPa). At end-systole, the mean YM values from the two groups were similar (175.84 kPa versus 200.2 kPa). More interestingly, H-Group end-systole mean YM was 126% higher that its end-diastole value, while I-Group end-systole mean YM was only 29% higher that its end-diastole value. This indicated that H-Group had much greater systole–diastole material stiffness variations. At beginning-of-ejection (BE), LV ejection fraction (LVEF) showed positive correlation with C-curvature, stress, and strain, and negative correlation with LV volume, respectively. At beginning-of-filling (BF), LVEF showed positive correlation with C-curvature and strain, but negative correlation with stress and LV volume, respectively. Using averaged values of two groups at BE, I-Group stress, strain, and wall thickness were 32%, 29%, and 18% lower (thinner), respectively, compared to those of H-Group. L-curvature from I-Group was 61% higher than that from H-Group. Difference in C-curvature between the two groups was not statistically significant. Our results indicated that our modeling approach has the potential to determine in vivo ventricle material properties, which in turn could lead to methods to infer presence of infarct from LV contractibility and material stiffness variations. Quantitative differences in LV volume, curvatures, stress, strain, and wall thickness between the two groups were provided.

scholarly journals Can we obtain in vivo transmural mean hoop stress of the aortic wall without knowing patient-specific material properties and residual deformations?

2018 ◽  
Author(s):  
Minliang Liu ◽  
Liang Liang ◽  
Haofei Liu ◽  
Ming Zhang ◽  
Caitlin Martin ◽  
...  
Keyword(s):  
Material Properties ◽  
Hoop Stress ◽  
Aortic Wall ◽  
Patient Specific ◽  
Membrane Stress ◽  
Penalty Approach ◽  
Thin Walled ◽  
Specific Material ◽  
Residual Deformations

AbstractIt is well known that residual deformations/stresses alter the mechanical behavior of arteries, e.g. the pressure-diameter curves. In an effort to enable personalized analysis of the aortic wall stress, approaches have been developed to incorporate experimentally-derived residual deformations into in vivo loaded geometries in finite element simulations using thick-walled models. Solid elements are typically used to account for “bending-like” residual deformations. Yet, the difficulty in obtaining patient-specific residual deformations and material properties has become one of the biggest challenges of these thick-walled models. In thin-walled models, fortunately, static determinacy offers an appealing prospect that allows for the calculation of the thin-walled membrane stress without patient-specific material properties. The membrane stress can be computed using forward analysis by enforcing an extremely stiff material property as penalty treatment, which is referred to as the forward penalty approach. However, thin-walled membrane elements, which have zero bending stiffness, are incompatible with the residual deformations, and therefore, it is often stated as a limitation of thin-walled models. In this paper, by comparing the predicted stresses from thin-walled models and thick-walled models, we demonstrate that the transmural mean hoop stress is the same for the two models and can be readily obtained from in vivo clinical images without knowing the patient-specific material properties and residual deformations. Computation of patient-specific mean hoop stress can be greatly simplified by using membrane model and the forward penalty approach, which may be clinically valuable.

Abstract 16230: Pulmonary Autograft Wall Stresses One Year After Ross Operation

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Edgardo Alonso ◽  
Yue XUAN ◽  
Alexander Emmott ◽  
Zhongjie Wang ◽  
Shalni Kumar ◽  
...  
Keyword(s):  
Ascending Aorta ◽  
Patient Specific ◽  
Principal Stresses ◽  
Ross Operation ◽  
Children And Young Adults ◽  
Specific Material ◽  
One Year ◽  
Patients Experience

Introduction: The Ross procedure is an excellent option for children and young adults who need aortic valve replacement as this surgery can restore patient survival to that of a normal sex and aged-matched population. However, some patients experience aneurysmal formation during autograft remodeling and require reoperation. As the underlying biomechanics of autograft remodeling are unknown, we investigated patient-specific wall stresses in pulmonary autografts one year post-operatively to better understand systemic pressure-driven early autograft wall stresses. Methods: Ross patients (n=16) who underwent intraoperative collection of pulmonary root/aortic specimen, and subsequent one-year MRI follow-up were recruited. Patient-specific material properties from their tissue were experimentally determined and incorporated into autograft ± Dacron and ascending aorta finite element models. A multiplicative approach was used to account for pre-stress geometry from in-vivo MRI. Physiologic pressure loading was simulated with LS-DYNA software. Results: At systemic systole, first principal stresses were 567kPa (25-75% IQR, 485-675kPa), 809kPa (691-1219kPa), and 382kPa (334-413kPa) at autograft sinuses, sinotubular junction (STJ), and ascending aorta, respectively. Second principal stresses were 355kPa (320-394kPa), 360kPa (310-426kPa), and 184kPa (147-222kPa) at autograft sinuses, STJ, and ascending aorta, respectively. Mean autograft diameters were 38.3±5.3mm, 29.9±2.7mm, and 26.6±4.0mm at sinuses, STJ, and annulus, respectively. Conclusions: First principal stresses were mainly located at STJ, particularly when Dacron reinforcement was applied to constrain STJ dilatation. However, at one-year after the Ross operation, autograft dilatation was not seen despite elevated autograft wall stresses compared to their internal controls, the lower wall stresses in corresponding native distal ascending aorta. In this group of patients, higher risk of dilatation is expected in the sinuses and STJ if not constrained by Dacron than the corresponding ascending aorta. Future follow-up will elucidate the biomechanics of long-term autograft remodeling to develop predictive models for autograft dilatation.

Impact of Patient-Specific In Vivo Vessel Material Properties on Carotid Atherosclerotic Plaque Stress/Strain Calculations

2019 ◽  
Vol 16 (03) ◽  
pp. 1842002 ◽  
Author(s):  
Qingyu Wang ◽  
Dalin Tang ◽  
Gador Canton ◽  
Thomas S. Hatsukami ◽  
Kristen L. Billiar ◽  
...  
Keyword(s):  
Material Properties ◽  
Carotid Plaque ◽  
Computational Models ◽  
Patient Specific ◽  
Stress And Strain ◽  
Carotid Atherosclerotic Plaque ◽  
Plaque Vulnerability ◽  
Material Models ◽  
Vessel Material

Patient-specific vessel material properties are in general lacking in image-based computational models. Carotid plaque stress and strain conditions with in vivo material and old material models were investigated (8 patients, 16 plaques). Plaque models using patient-specific in vivo vessel material properties showed significant differences from models using old material properties from the literature on stress and strain calculations. These differences demonstrated that models using in vivo material properties could improve the accuracy of stress and strain calculations which could potentially lead to more accurate plaque vulnerability assessment.

Deformable Image Registration Between Cardiac PET Images Encompassing a Range of Physical Heart Sizes

2011 ◽  
Author(s):  
Benjamin R. Coleman ◽  
Alexander I. Veress
Keyword(s):  
Mechanical Performance ◽  
Fe Analysis ◽  
Material Behavior ◽  
Patient Specific ◽  
Stress And Strain ◽  
Myocardial Tissue ◽  
Cardiac Pet ◽  
Considerable Research ◽  
Deformation Stress

Cardiac mechanical performance depends upon myocardial tissue elongation and contraction. Deformation, stress and strain within the myofibers provide valuable information about potential tissue adaptation [1]. Specifically, the stress state of the tissue is believed to drive remodeling of the myocardium. Because it is not possible to measure in-vivo stress in the human heart, considerable research has gone into developing patient specific, mathematical models of the heart based on finite element (FE) analysis and cardiac imaging [2, 3]. Stress estimates from these models could yield valuable information about of the material behavior of the myocardium that would provide valuable information for research into cardiac pathologies.

A novel ultrasound technique to study the biomechanics of the human esophagus in vivo

2002 ◽  
Vol 282 (5) ◽  
pp. G785-G793 ◽  
Author(s):  
Torahiko Takeda ◽  
Ghassan Kassab ◽  
Jianmin Liu ◽  
James L. Puckett ◽  
Rishi R. Mittal ◽  
...  
Keyword(s):  
Circumferential Stress ◽  
In Vivo Studies ◽  
Esophageal Wall ◽  
Stress And Strain ◽  
Stress Strain ◽  
Healthy Human ◽  
Ultrasound Technique ◽  
Human Esophagus

The objectives of this study were to validate a novel ultrasound technique and to use it to study the circumferential stress-strain properties of the human esophagus in vivo. A manometric catheter equipped with a high-compliance bag and a high-frequency intraluminal ultrasonography probe was used to record esophageal pressure and images. Validation studies were performed in vitro followed by in vivo studies in healthy human subjects. Esophageal distensions were performed with either an isovolumic (5–20 ml of water) or with an isobaric (10–60 mmHg) technique. Sustained distension was also performed for 3 min in each subject. The circumferential wall stress and strain were calculated. In vitro studies indicate that the ultrasound technique can make measurements of the esophageal wall with an accuracy of 0.01 mm. The in vivo studies provide the necessary data to compute the Kirchhoff's stress, Green's strain, and Young's elastic modulus during esophageal distensions. The stress-strain relationship revealed a linear shape, the slope of which corresponds to the Young's modulus. During sustained distensions, we found dynamic changes of stress and strain during the period of distension. We describe and validate a novel ultrasound technique that allows measurement of biomechanical properties of the esophagus in vivo in humans.

Patient-Specific Finite Element Modeling of Mitral Valve Dynamic Deformation

2012 ◽  
Author(s):  
Qian Wang ◽  
Wei Sun
Keyword(s):  
Finite Element ◽  
Mitral Valve ◽  
Left Ventricle ◽  
Dynamic Deformation ◽  
Patient Specific ◽  
Stress And Strain ◽  
Prosthetic Devices ◽  
In Vivo Experiments ◽  
Normal Mitral Valve

Mitral valve is a two-leaflet valve that is located between the left atrium and the left ventricle of the heart. In order to successfully replace or repair mitral valve and develop effective prosthetic devices, it is critical to understand the in vivo mechanics of the normal mitral valve. Although research has been conducted to investigate animal mitral valve strains by in vivo experiments, it is still very challenging to obtain accurate in vivo stress and strain information of the human mitral valve.

scholarly journals 3D MRI-Based Anisotropic FSI Models With Cyclic Bending for Human Coronary Atherosclerotic Plaque Mechanical Analysis

2009 ◽  
Vol 131 (6) ◽  
Author(s):  
Dalin Tang ◽  
Chun Yang ◽  
Shunichi Kobayashi ◽  
Jie Zheng ◽  
Pamela K. Woodard ◽  
...  
Keyword(s):  
Atherosclerotic Plaque ◽  
Vulnerability Assessment ◽  
Computational Models ◽  
Plaque Rupture ◽  
Maximum Velocity ◽  
Coronary Plaque ◽  
Plaque Vulnerability ◽  
Stress Strain ◽  
Axial Stretch ◽  
Cyclic Bending

Heart attack and stroke are often caused by atherosclerotic plaque rupture, which happens without warning most of the time. Magnetic resonance imaging (MRI)-based atherosclerotic plaque models with fluid-structure interactions (FSIs) have been introduced to perform flow and stress/strain analysis and identify possible mechanical and morphological indices for accurate plaque vulnerability assessment. For coronary arteries, cyclic bending associated with heart motion and anisotropy of the vessel walls may have significant influence on flow and stress/strain distributions in the plaque. FSI models with cyclic bending and anisotropic vessel properties for coronary plaques are lacking in the current literature. In this paper, cyclic bending and anisotropic vessel properties were added to 3D FSI coronary plaque models so that the models would be more realistic for more accurate computational flow and stress/strain predictions. Six computational models using one ex vivo MRI human coronary plaque specimen data were constructed to assess the effects of cyclic bending, anisotropic vessel properties, pulsating pressure, plaque structure, and axial stretch on plaque stress/strain distributions. Our results indicate that cyclic bending and anisotropic properties may cause 50–800% increase in maximum principal stress (Stress-P1) values at selected locations. The stress increase varies with location and is higher when bending is coupled with axial stretch, nonsmooth plaque structure, and resonant pressure conditions (zero phase angle shift). Effects of cyclic bending on flow behaviors are more modest (9.8% decrease in maximum velocity, 2.5% decrease in flow rate, 15% increase in maximum flow shear stress). Inclusion of cyclic bending, anisotropic vessel material properties, accurate plaque structure, and axial stretch in computational FSI models should lead to a considerable improvement of accuracy of computational stress/strain predictions for coronary plaque vulnerability assessment. Further studies incorporating additional mechanical property data and in vivo MRI data are needed to obtain more complete and accurate knowledge about flow and stress/strain behaviors in coronary plaques and to identify critical indicators for better plaque assessment and possible rupture predictions.

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