Abstract 1122‐000213: Presence of Blebs Associated with Reduced Aneurysm Wall Tension and Increased Wall Enhancement

2021 ◽  
Vol 1 (S1) ◽  
Author(s):  
Ashrita Raghuram ◽  
Adam E Galloy ◽  
Marco A Nino ◽  
Alberto Varon Miller ◽  
Sebastian Sanchez ◽  
...  
Keyword(s):  
Material Model ◽  
Strongly Correlated ◽  
Wall Tension ◽  
Element Analysis ◽  
Neck Size ◽  
Aneurysm Neck ◽  
Aneurysm Wall ◽  
Unruptured Intracranial Aneurysms ◽  
Contour Plots ◽  
Uniform Wall

Introduction : Aneurysm wall enhancement using high‐resolution vessel wall imaging (HR‐VWI) may provide new surrogate biomarkers for instability. Finite element analysis (FEA) paired with HR‐VWI can provide more insight into complex morphological features that ultimately lead to aneurysm growth and rupture. Methods : Unruptured intracranial aneurysms were reconstructed in 3D from CE‐MRA imaging. Shells were created assuming a uniform wall thickness of 86 μm and FEA was conducted with a 3rd order polynomial material model, assuming the wall to be isotropic, homogenous, and similar between subjects. The 95th percentile wall tension was defined as high wall tension to account for mesh artifacts. Low wall tension was identified from nodal values and verified on contour plots. Regions of high and low wall tension were characterized from contour plots. Aneurysms were measured and classified as enhancing (CR stalk ≥0.6) or non‐enhancing (CR stalk <0.6), using manual ROI measurements from 3T HR‐VWI T1 postcontrast imaging. Results : Of the twenty‐three aneurysms analyzed, fourteen were classified as enhancing (CR stalk ≥0.6) and nine as non‐enhancing. Enhancing aneurysms had a significantly higher 95th percentile wall tension (m = 0.89±0.32 N/cm) compared to non‐enhancing aneurysms (m = 0.48±0.10 N/cm, p<0.001). Wall enhancement remained a significant predictor of wall tension while accounting for the effects of aneurysm size (p = 0.046). High wall tension was consistently concentrated at the neck of the aneurysm, while low wall tension concentrated at the dome. (Figure 1). Aneurysms with blebs (N = 7) had significantly lower minimal wall tension (m = 0.13±0.02 N/cm) than those without (m = 0.21±0.10 N/cm, p = 0.033). Enhancing aneurysms had significantly higher minimal wall tensions (m = 0.23±0.10 N/cm), than non‐enhancing aneurysms (m = 0.13±0.02 N/cm, 0.003). Minimal wall tension was less strongly correlated with diameter and neck size (Spearman’s r = 0.564,0.378 respectively) than 95th percentile wall tension (Spearman’s r = 0.756, 0.541 respectively). Conclusions : Large and irregular aneurysms are subject to complex mechanical loading. The resultant stress concentrators may prompt the histological remodeling response observed in areas of growth, like the aneurysm neck. Low wall tension indicative of wall degradation in areas more prone to rupture colocalized with aneurysm wall enhancement and blebs.

scholarly journals Analysis of Cerebral Aneurysm Wall Tension and Enhancement Using Finite Element Analysis and High-Resolution Vessel Wall Imaging

2021 ◽  
Vol 12 ◽  
Author(s):  
Adam E. Galloy ◽  
Ashrita Raghuram ◽  
Marco A. Nino ◽  
Alberto Varon Miller ◽  
Ryan Sabotin ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
High Resolution ◽  
Vessel Wall ◽  
Intracranial Aneurysms ◽  
Vessel Wall Imaging ◽  
Wall Tension ◽  
Element Analysis ◽  
Aneurysm Wall ◽  
Wall Imaging

Biomechanical computational simulation of intracranial aneurysms has become a promising method for predicting features of instability leading to aneurysm growth and rupture. Hemodynamic analysis of aneurysm behavior has helped investigate the complex relationship between features of aneurysm shape, morphology, flow patterns, and the proliferation or degradation of the aneurysm wall. Finite element analysis paired with high-resolution vessel wall imaging can provide more insight into how exactly aneurysm morphology relates to wall behavior, and whether wall enhancement can describe this phenomenon. In a retrospective analysis of 23 unruptured aneurysms, finite element analysis was conducted using an isotropic, homogenous third order polynomial material model. Aneurysm wall enhancement was quantified on 2D multiplanar views, with 14 aneurysms classified as enhancing (CRstalk≥0.6) and nine classified as non-enhancing. Enhancing aneurysms had a significantly higher 95th percentile wall tension (μ = 0.77 N/cm) compared to non-enhancing aneurysms (μ = 0.42 N/cm, p &lt; 0.001). Wall enhancement remained a significant predictor of wall tension while accounting for the effects of aneurysm size (p = 0.046). In a qualitative comparison, low wall tension areas concentrated around aneurysm blebs. Aneurysms with irregular morphologies may show increased areas of low wall tension. The biological implications of finite element analysis in intracranial aneurysms are still unclear but may provide further insights into the complex process of bleb formation and aneurysm rupture.

scholarly journals Cost analysis of materials used in the endovascular treatment of unruptured intracranial aneurysms in Mexico

2020 ◽  
Vol 26 (4) ◽  
pp. 476-482
Author(s):  
Jose A Figueroa-Sanchez ◽  
Ana S Ferrigno ◽  
David E Hinojosa-González ◽  
Gustavo Salgado-Garza ◽  
Hector R Martinez ◽  
...  
Keyword(s):  
Endovascular Treatment ◽  
Low Income ◽  
Intracranial Aneurysms ◽  
Neck Size ◽  
Aneurysm Neck ◽  
Material Cost ◽  
Unruptured Intracranial Aneurysms ◽  
Intervention Cost ◽  
Materials Used ◽  
The Cost

Background To prevent the potentially fatal consequences of intracranial aneurysmal rupture, exclusion from the circulation can be achieved through an endovascular approach. However, the elevated cost of such procedures can be prohibitive for patients in low resource settings. The objective of this study is to identify the factors that modify the cost of the materials used for endovascular treatment of unruptured intracranial aneurysms. Methods Medical records of patients who underwent an endovascular treatment for unruptured intracranial aneurysms between June 2013 and June 2019 in a hospital located in Northeast Mexico were reviewed. Descriptive statistics of the cost of consumable materials used during the procedure was performed, and a regression model was undertaken to examine potential associations between the studied variables and total cost of the intervention. Results A total of 128 patients were included in this analysis. The average intervention cost was $21,687.22 USD. The variables associated with increased material cost were aneurysm size (p = 0.03), aneurysm neck size (p < 0.001), and aneurysm localization in the cavernous segment of the internal carotid artery (p = 0.01). Other variables such as patient age and sex, other aneurysm localizations, laterality of the aneurysm, performing neurointerventionalist, and presence of intervention complications were not statistically significant. Conclusions To our knowledge, this is the first study that examines the variables associated with the material cost of endovascular treatment of unruptured intracranial aneurysms. Awareness of which elements are important drivers of materials’ costs provides a strategic advantage when making hospital administrative decisions and attempting to improve access to endovascular treatment in countries of low income.

scholarly journals On the Role of Modeling Choices in Estimation of Cerebral Aneurysm Wall Tension

2011 ◽  
Author(s):  
Manasi Ramachandran ◽  
Shouhua Hu ◽  
Jia Lu ◽  
Aki Laakso ◽  
Robert E. Harbaugh ◽  
...  
Keyword(s):  
Cerebral Aneurysm ◽  
Material Model ◽  
Significant Error ◽  
Inverse Solution ◽  
Patient Specific ◽  
Elastic Model ◽  
Wall Tension ◽  
Specific Level ◽  
Solution Scheme ◽  
Aneurysm Wall

Estimations of pressure-induced tension in the cerebral aneurysm sac wall may serve as metrics that help stratify patients according to rupture risk. Beyond segmentation of patient-specific aneurysm geometries, many modeling choices may be made in order to numerically estimate pressure-induced aneurysm wall tension. Some of these key choices are: 1) the material model and its parameters (this is unknown at a patient-specific level); 2) whether or not to accommodate bending deformation (membrane versus shell); 3) whether and how much of vasculature to include in domain of analysis; and 4) how to address the lack of zero-pressure geometry (forward versus inverse solution schemes). Often, the focus is on what the best of these modeling choices are. In an ideal world, appropriate modeling choices would be the use of an anisotropic finite elastic model [1–2], shell-like behavior [3], a large enough vasculature in the analysis domain to minimize edge-effects at the aneurysm sac, and an inverse solution scheme [3] to address the pre-deformed nature of the sac under in vivo imaging. But are these rigorous modeling choices really that necessary? Would compromising on these choices translate into significant error in the findings? We submit that, to the extent that the goal is to stratify patients according to sac wall tension, modeling choices are really secondary and will not translate into significant error in our interpretations. The objective of this study is to test the importance of three of these modeling choices — material model, truncation of vasculature in analysis domain and solution scheme (forward versus inverse) — in stratifying aneurysms based on wall tension using aneurysms in a study population.

scholarly journals Association of Menopausal Age with Unruptured Intracranial Aneurysm Morphology

2019 ◽  
Vol 8 (2-6) ◽  
pp. 109-115 ◽  
Author(s):  
Sushrut Dharmadhikari ◽  
Kunakorn Atchaneeyasakul ◽  
Sudheer Ambekar ◽  
Vasu Saini ◽  
Diogo C. Haussen ◽  
...  
Keyword(s):  
Treatment Outcomes ◽  
Endovascular Therapy ◽  
Care Center ◽  
Tertiary Care ◽  
Neck Size ◽  
Younger Women ◽  
Aneurysm Neck ◽  
Maximal Diameter ◽  
Unruptured Intracranial Aneurysms ◽  
The Impact

Background: The prevalence of unruptured intracranial aneurysms (UIAs) increases rapidly in aging women compared with younger women. The impact of menopausal age on UIAs and treatment outcomes with endovascular therapy has not been well studied. We hypothesized that premenopausal age may have a protective effect on presentation size and treatment outcomes. Objective: To evaluate the association of menopause with UIA size and outcome with endovascular therapy. Methods: Retrospective analysis of consecutive female patients with UIAs treated with endovascular therapy at our academic tertiary care center. UIA characteristics, complications, and outcomes were recorded and compared. Results: 117 patients were included: 23 patients in the premenopausal age (PRM) group and 94 in the postmenopausal age (POM) group. 93.6% of all aneurysms in the PRM group were in the internal carotid artery (ICA) segments (p < 0.05). Hence only ICA segment aneurysms were further studied. A total of 21 patients in the PRM group and 60 in the POM group were found to have ICA segment aneurysms. Baseline characteristics were similar between the 2 groups. The mean size of the aneurysms in the PRM group was 8.6 ± 3.9 versus 10.8 ± 5.6 mm in the POM group (p = 0.055). There was a trend to higher aneurysm neck size seen in the POM group (4.7 ± 2.5 vs. 3.7 ± 1.7 mm; p = 0.07). The number of aneurysm lobes was higher in the PRM group (1.23 ± 0.54 vs. 1.07 ± 0.31; p = 0.18). In multivariate analysis, the PRM group had a significantly higher number of UIA lobes. Complications and endovascular therapy outcomes were similar between the 2 groups. Conclusions: A trend to increased UIA maximal diameter and neck size was seen in the POM group compared to the PRM group. The PRM group had a significantly higher number of UIA lobes. Larger prospective trials are needed to confirm these findings.

Lifetime Prediction of Tires with Regard to Oxidative Aging5

2008 ◽  
Vol 36 (1) ◽  
pp. 63-79 ◽  
Author(s):  
L. Nasdala ◽  
Y. Wei ◽  
H. Rothert ◽  
M. Kaliske
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Temperature Distribution ◽  
Superposition Principle ◽  
Accelerated Aging ◽  
Material Model ◽  
Aging Behavior ◽  
Element Analysis ◽  
Material Parameters ◽  
Reaction Processes

Abstract It is a challenging task in the design of automobile tires to predict lifetime and performance on the basis of numerical simulations. Several factors have to be taken into account to correctly estimate the aging behavior. This paper focuses on oxygen reaction processes which, apart from mechanical and thermal aspects, effect the tire durability. The material parameters needed to describe the temperature-dependent oxygen diffusion and reaction processes are derived by means of the time–temperature–superposition principle from modulus profiling tests. These experiments are designed to examine the diffusion-limited oxidation (DLO) effect which occurs when accelerated aging tests are performed. For the cord-reinforced rubber composites, homogenization techniques are adopted to obtain effective material parameters (diffusivities and reaction constants). The selection and arrangement of rubber components influence the temperature distribution and the oxygen penetration depth which impact tire durability. The goal of this paper is to establish a finite element analysis based criterion to predict lifetime with respect to oxidative aging. The finite element analysis is carried out in three stages. First the heat generation rate distribution is calculated using a viscoelastic material model. Then the temperature distribution can be determined. In the third step we evaluate the oxygen distribution or rather the oxygen consumption rate, which is a measure for the tire lifetime. Thus, the aging behavior of different kinds of tires can be compared. Numerical examples show how diffusivities, reaction coefficients, and temperature influence the durability of different tire parts. It is found that due to the DLO effect, some interior parts may age slower even if the temperature is increased.

Cord/Rubber Material Properties

1985 ◽  
Vol 58 (4) ◽  
pp. 830-856 ◽  
Author(s):  
R. J. Cembrola ◽  
T. J. Dudek
Keyword(s):  
Finite Element ◽  
Material Model ◽  
Rubber Composites ◽  
Stress Strain ◽  
Element Analysis ◽  
Rubber Layer ◽  
Strain Behavior ◽  
Nonlinear Stress ◽  
Interlaminar Shear ◽  
Mechanics Of Composite Materials

Abstract Recent developments in nonlinear finite element methods (FEM) and mechanics of composite materials have made it possible to handle complex tire mechanics problems involving large deformations and moderate strains. The development of an accurate material model for cord/rubber composites is a necessary requirement for the application of these powerful finite element programs to practical problems but involves numerous complexities. Difficulties associated with the application of classical lamination theory to cord/rubber composites were reviewed. The complexity of the material characterization of cord/rubber composites by experimental means was also discussed. This complexity arises from the highly anisotropic properties of twisted cords and the nonlinear stress—strain behavior of the laminates. Micromechanics theories, which have been successfully applied to hard composites (i.e., graphite—epoxy) have been shown to be inadequate in predicting some of the properties of the calendered fabric ply material from the properties of the cord and rubber. Finite element models which include an interply rubber layer to account for the interlaminar shear have been shown to give a better representation of cord/rubber laminate behavior in tension and bending. The application of finite element analysis to more refined models of complex structures like tires, however, requires the development of a more realistic material model which would account for the nonlinear stress—strain properties of cord/rubber composites.

Thermo-Mechanical Modeling and Analysis of Equal Channel Angular Pressing

2005 ◽  
Vol 23 ◽  
pp. 263-266 ◽  
Author(s):  
Qing Xiang Pei ◽  
B.H. Hu ◽  
C. Lu
Keyword(s):  
Equal Channel Angular Pressing ◽  
Temperature Rise ◽  
Flow Behavior ◽  
Material Model ◽  
Workpiece Material ◽  
Element Analysis ◽  
Modeling And Analysis ◽  
Die Geometry ◽  
Angular Pressing ◽  
Good Agreement

Thermo-mechanical finite element analysis was carried out to study the deformation behavior and temperature distribution during equal channel angular pressing (ECAP). The material model used is the Johnson-Cook constitution model that can consider the multiplication effect of strain, strain rate, and temperature on the flow stress. The effects of pressing speed, pressing temperature, workpiece material and die geometry on the temperature rise and flow behavior during ECAP process were investigated. The simulated temperature rise due to deformation heating was compared with published experimental results and a good agreement was obtained. Among the various die geometries studied, the two-turn die with 0° round corner generates the highest and most uniform plastic strain in the workpiece.

scholarly journals A Material Model for the Orthotropic and Viscous Behavior of Separators in Lithium-Ion Batteries under High Mechanical Loads

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4585
Author(s):  
Marian Bulla ◽  
Stefan Kolling ◽  
Elham Sahraei
Keyword(s):  
Mechanical Behavior ◽  
Lithium Ion ◽  
Material Model ◽  
Tensile Tests ◽  
Element Analysis ◽  
Rate Dependent ◽  
Novel Material ◽  
Li Ion ◽  
Role Based ◽  
Drive Systems

The present study is focused on the development of a material model where the orthotropic-visco-elastic and orthotropic-visco-plastic mechanical behavior of a polymeric material is considered. The increasing need to reduce the climate-damaging exhaust gases in the automotive industry leads to an increasing usage of electric powered drive systems using Lithium-ion (Li-ion) batteries. For the safety and crashworthiness investigations, a deeper understanding of the mechanical behavior under high and dynamic loads is needed. In order to prevent internal short circuits and thermal runaways within a Li-ion battery, the separator plays a crucial role. Based on results of material tests, a novel material model for finite element analysis (FEA) is developed using the explicit solver Altair Radioss. Based on this model, the visco-elastic-orthotropic, as well as the visco-plastic-orthotropic, behavior until failure can be modeled. Finally, a FE simulation model of the separator material is performed, using the results of different tensile tests conducted at three different velocities, 0.1 mm·s−1, 1.0 mm·s−1 and 10.0 mm·s−1 and different orientations of the specimen. The purpose is to predict the anisotropic, rate-dependent stiffness behavior of separator materials in order to improve FE simulations of the mechanical behavior of batteries and therefore reduce the development time of electrically powered vehicles and consumer goods. The present novel material model in combination with a well-suited failure criterion, which considers the different states of stress and anisotropic-visco-dependent failure limits, can be applied for crashworthiness FE analysis. The model succeeded in predicting anisotropic, visco-elastic orthotropic and visco-plastic orthotropic stiffness behavior up to failure.

Polycrystal Simulations Investigating the Effect of Additional Slip System Availability in a 6063 Aluminum Alloy at Elevated Temperature

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Antoinette M. Maniatty ◽  
David J. Littlewood ◽  
Jing Lu
Keyword(s):  
Aluminum Alloy ◽  
Elevated Temperature ◽  
Compression Test ◽  
Elevated Temperatures ◽  
Material Model ◽  
Grain Structure ◽  
Slip Systems ◽  
Modeling Framework ◽  
Element Analysis ◽  
6063 Aluminum Alloy

In order to better understand and predict the intragrain heterogeneous deformation in a 6063 aluminum alloy deformed at an elevated temperature, when additional slip systems beyond the usual octahedral slip systems are active, a modeling framework for analyzing representative polycrystals under these conditions is presented. A model polycrystal that has a similar microstructure to that observed in the material under consideration is modeled with a finite element analysis. A large number of elements per grain (more than 1000) are used to capture well the intragranular heterogeneous response. The polycrystal model is analyzed with three different sets of initial orientations. A compression test is used to calibrate the material model, and a macroscale simulation of the compression test is used to define the deformation history applied to the model polycrystal. In order to reduce boundary condition effects, periodic boundary conditions are applied to the model polycrystal. To investigate the effect of additional slip systems expected to be active at elevated temperatures, the results considering only the 12 {111}⟨110⟩ slip systems are compared to the results with the additional 12 {110}⟨110⟩ and {001}⟨110⟩ slip systems available (i.e., 24 available slip systems). The resulting predicted grain structure and texture are compared to the experimentally observed grain structure and texture in the 6063 aluminum alloy compression sample as well as to the available data in the literature, and the intragranular misorientations are studied.

The Dynamic Stress Characteristics of Air-Decked Bench Blasting under Soft Interlayer

2011 ◽  
Vol 101-102 ◽  
pp. 400-404
Author(s):  
Liang Wu ◽  
Dong Xiao Yu ◽  
Wei Dong Duan
Keyword(s):  
Dynamic Stress ◽  
Near Field ◽  
Blast Hole ◽  
Material Model ◽  
Explosion Energy ◽  
Element Analysis ◽  
Charge Structure ◽  
Soft Interlayer ◽  
Bench Blasting ◽  
Project Construction

In modern mining and project construction, how to make use of the explosion energy effectively is the key technology demanding prompt solution at present. The application of air-decked blasting technology has enabled the efficient use of explosion energy, which proves that the air-decked blasting technology can overcome many disadvantages caused by column charge effectively, getting ideal explosion effect. Based on the dynamic finite element analysis software with the material model of Mat-Plastic-Kinemetic, the dynamic stress characteristics and failure mechanism of blast-hole near-field with level soft interlayer are researched with different air-decked charge structures. There is significant effect on the rock at the middle of blast-hole if top-air-decked charge structure with indirect initiation and middle-air-decked charge structure with two ends initiation at the same time. If bottom-air-decked charge structure with indirect initiation, soft inter-layer don’t change the peek of compression and tensile stress curves of typical elements with distance from the bottom of hole, so there is not effect significantly of level soft interlayer on bottom-air-decked charge structure with indirect initiation.

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