Biomechanical Mechanisms and Hemodynamics in the Case of Stenosis

2019 ◽  
Vol 9 (10) ◽  
pp. 1334-1338
Author(s):  
Yu-Chou Huang ◽  
Han-Yi Cheng
Keyword(s):  
Mechanical Properties ◽  
Finite Element Method ◽  
Finite Element ◽  
Blood Flow ◽  
Magnetic Resonance ◽  
Blood Flow Velocity ◽  
Three Dimensional ◽  
Vascular Wall ◽  
Magnetic Resonance Images ◽  
Artery Segment

The objective of the present study is to investigate the blood flow of the artery with stenosis using finite element method. Three-dimensional 3-D artery models were reconstructed to simulate blood hemodynamic behaviors from magnetic resonance images. Many papers have studied 3-D finite element artery models, but few have examined the effects of different stenosis thicknesses in arteries. It is imperative to incorporate the mechanical properties of a diseased artery segment into treatment planning because stress is a strong biological trigger that directs atherosclerosis protection. Stress may also have predictive value to pinpoint regions at risk for restenosis. The results showed that stenosis of a 1 mm thickness decreased the blood flow velocity about 48%. This confirmed that stenosis also induces abnormal stress in the narrowest position of a vascular wall. This research provides information for arteries with stenosis in clinical treatment.

Cerebral blood flow velocity underestimates cerebral blood flow during modest hypercapnia and hypocapnia

2014 ◽  
Vol 117 (10) ◽  
pp. 1090-1096 ◽  
Author(s):  
Nicole S. Coverdale ◽  
Joseph S. Gati ◽  
Oksana Opalevych ◽  
Amanda Perrotta ◽  
J. Kevin Shoemaker
Keyword(s):  
Carbon Dioxide ◽  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Magnetic Resonance ◽  
Flow Velocity ◽  
Blood Flow Velocity ◽  
Cerebral Blood Flow Velocity ◽  
Intraclass Correlation ◽  
Magnetic Resonance Images ◽  
Carbon Dioxide Partial Pressure

To establish the accuracy of transcranial Doppler ultrasound (TCD) measures of middle cerebral artery (MCA) cerebral blood flow velocity (CBFV) as a surrogate of cerebral blood flow (CBF) during hypercapnia (HC) and hypocapnia (HO), we examined whether the cross-sectional area (CSA) of the MCA changed during HC or HO and whether TCD-based estimates of CBFV were equivalent to estimates from phase contrast (PC) magnetic resonance imaging. MCA CSA was measured from 3T magnetic resonance images during baseline, HO (hyperventilation at 30 breaths/min), and HC (6% carbon dioxide). PC and TCD measures of CBFV were measured during these protocols on separate days. CSA and TCD CBFV were used to calculate CBF. During HC, CSA increased from 5.6 ± 0.8 to 6.5 ± 1.0 mm2 ( P < 0.001, n = 13), while end-tidal carbon dioxide partial pressure (PetCO2) increased from 37 ± 3 to 46 ± 5 Torr ( P < 0.001). During HO, CSA decreased from 5.8 ± 0.9 to 5.3 ± 0.9 mm2 ( P < 0.001, n = 15), while PetCO2 decreased from 36 ± 4 to 23 ± 3 Torr ( P < 0.001). CBFVs during baseline, HO, and HC were compared between PC and TCD, and the intraclass correlation coefficient was 0.83 ( P < 0.001). The relative increase from baseline was 18 ± 8% greater ( P < 0.001) for CBF than TCD CBFV during HC, and the relative decrease of CBF during HO was 7 ± 4% greater than the change in TCD CBFV ( P < 0.001). These findings challenge the assumption that the CSA of the MCA does not change over modest changes in PetCO2.

Application of Finite Element Method to the Simulation of Vessel Stents

2014 ◽  
Vol 804 ◽  
pp. 243-247 ◽  
Author(s):  
Dinh van Hai ◽  
Hoang Minh Tam ◽  
Duong van Quang
Keyword(s):  
Finite Element Method ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Stainless Steel ◽  
Blood Flow ◽  
316L Stainless Steel ◽  
Simulation And Modeling ◽  
Element Analysis ◽  
Study Results ◽  
Artery Segment

In this study, the effects of supereslasticity of Nitinol for self-expanding (SX) stents – Stent devices which are implanted into the blood vessels in order to restore blood flow in a diseased artery segment (narrowing of the blood vessel due to plaque build-up) and keep the artery open after angioplasty were considered and analyzed. To emphasize the unique properties of Nitinol as compared to other materials, this study was conducted to differentiate the behaviors of two types of stents which are made of Nititol and 316L stainless steel during implantation. Finite element analysis was used for simulation and modeling. The study results are expected to serve well the design of vessel stents.

Development and Validation of a Three-Dimensional Finite Element Model of the Face

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
G. G. Barbarino ◽  
M. Jabareen ◽  
J. Trzewik ◽  
A. Nkengne ◽  
G. Stamatas ◽  
...  
Keyword(s):  
Finite Element ◽  
Magnetic Resonance ◽  
Finite Element Model ◽  
Three Dimensional ◽  
Element Model ◽  
Magnetic Resonance Images ◽  
Dimensional Finite Element ◽  
The Face ◽  
Three Dimensional Finite Element ◽  
Tissue Aging

A detailed three-dimensional finite element model of the face is presented in this paper. Bones, muscles, skin, fat, and superficial muscoloaponeurotic system were reconstructed from magnetic resonance images and modeled according to anatomical, plastic, and reconstructive surgery literature. The finite element mesh, composed of hexahedron elements, was generated through a semi-automatic procedure with an effective compromise between the detailed representation of anatomical parts and the limitation of the computational time. Nonlinear constitutive equations are implemented in the finite element model. The corresponding model parameters were selected according to previous work with mechanical measurements on soft facial tissue, or based on reasonable assumptions. Model assumptions concerning tissue geometry, interactions, mechanical properties, and the boundary conditions were validated through comparison with experiments. The calculated response of facial tissues to gravity loads, to the application of a pressure inside the oral cavity and to the application of an imposed displacement was shown to be in good agreement with the data from corresponding magnetic resonance images and holographic measurements. As a first application, gravimetric soft tissue descent was calculated from the long time action of gravity on the face in the erect position, with tissue aging leading to a loss of stiffness. Aging predictions are compared with the observations from an “aging database” with frontal photos of volunteers at different age ranges (i.e., 20–40 years and 50–70 years).

Influence of Residual Stresses and Particle Properties on Mechanical Response of the Material in Particulate Ceramic Composites

2016 ◽  
Vol 713 ◽  
pp. 212-215 ◽  
Author(s):  
Kateřina Štegnerová ◽  
Luboš Náhlík ◽  
Pavel Hutař ◽  
Pavel Pokorný ◽  
Zdeněk Majer
Keyword(s):  
Mechanical Properties ◽  
Finite Element Method ◽  
Finite Element ◽  
Residual Stresses ◽  
Mechanical Behaviour ◽  
Mechanical Response ◽  
Three Dimensional ◽  
Ceramic Composites ◽  
Particle Properties ◽  
Three Dimensional Models

The contribution deals with the issue of mechanical response of the particulate ceramic composites used in microelectronic. Mechanical properties and behaviour of composites are highly influenced by residual stresses which are developed in material during cooling in manufacturing process due to the different coefficients of thermal expansions of individual constituents. The main aim of this paper is to estimate the elastic constants and strength of the selected particulate ceramic composites with considering the residual stresses. Three dimensional models and finite element method are used for numerical simulations. Results contribute to determination and better understanding of mechanical behaviour of the particulate ceramic composites.

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