scholarly journals Applicability assessment of a stent-retriever thrombectomy finite-element model

2020 ◽  
Vol 11 (1) ◽  
pp. 20190123 ◽  
Author(s):  
Giulia Luraghi ◽  
Jose Felix Rodriguez Matas ◽  
Gabriele Dubini ◽  
Francesca Berti ◽  
Sara Bridio ◽  
...  
Keyword(s):  
Finite Element ◽  
Numerical Model ◽  
Blood Circulation ◽  
Blood Clot ◽  
Invasive Procedure ◽  
Element Model ◽  
Stent Deployment ◽  
Numerical Finite Element

An acute ischaemic stroke appears when a blood clot blocks the blood flow in a cerebral artery. Intra-arterial thrombectomy, a mini-invasive procedure based on stent technology, is a mechanical available treatment to extract the clot and restore the blood circulation. After stent deployment, the clot, trapped in the stent struts, is pulled along with the stent towards a receiving catheter. Recent clinical trials have confirmed the effectiveness and safety of mechanical thrombectomy. However, the procedure requires further investigation. The aim of this study is the development of a numerical finite-element-based model of the thrombectomy procedure. In vitro thrombectomy tests are performed in different vessel geometries and one simulation for each test is carried out to verify the accuracy and reliability of the proposed numerical model. The results of the simulations confirm the efficacy of the model to replicate all the experimental setups. Clot stress and strain fields from the numerical analysis, which vary depending on the geometric features of the vessel, could be used to evaluate the possible fragmentation of the clot during the procedure. The proposed in vitro / in silico comparison aims at assessing the applicability of the numerical model and at providing validation evidence for the specific in vivo thrombectomy outcomes prediction.

Strain Measurement in Coronary Arteries Using Intravascular Ultrasound and Deformable Images

2002 ◽  
Vol 124 (6) ◽  
pp. 734-741 ◽  
Author(s):  
Alexander I. Veress ◽  
Jeffrey A. Weiss ◽  
Grant T. Gullberg ◽  
D. Geoffrey Vince ◽  
Richard D. Rabbitt
Keyword(s):  
Finite Element ◽  
Intravascular Ultrasound ◽  
Coronary Arteries ◽  
Strain Distribution ◽  
Plaque Rupture ◽  
Element Model ◽  
Cross Sectional ◽  
Image Pairs

Atherosclerotic plaque rupture is responsible for the majority of myocardial infarctions and acute coronary syndromes. Rupture is initiated by mechanical failure of the plaque cap, and thus study of the deformation of the plaque in the artery can elucidate the events that lead to myocardial infarction. Intravascular ultrasound (IVUS) provides high resolution in vitro and in vivo cross-sectional images of blood vessels. To extract the deformation field from sequences of IVUS images, a registration process must be performed to correlate material points between image pairs. The objective of this study was to determine the efficacy of an image registration technique termed Warping to determine strains in plaques and coronary arteries from paired IVUS images representing two different states of deformation. The Warping technique uses pointwise differences in pixel intensities between image pairs to generate a distributed body force that acts to deform a finite element model. The strain distribution estimated by image-based Warping showed excellent agreement with a known forward finite element solution, representing the gold standard, from which the displaced image was created. The Warping technique had a low sensitivity to changes in material parameters or material model and had a low dependency on the noise present in the images. The Warping analysis was also able to produce accurate strain distributions when the constitutive model used for the Warping analysis and the forward analysis was different. The results of this study demonstrate that Warping in conjunction with in vivo IVUS imaging will determine the change in the strain distribution resulting from physiological loading and may be useful as a diagnostic tool for predicting the likelihood of plaque rupture through the determination of the relative stiffness of the plaque constituents.

Finite-element analysis of stress in the canine diaphragm

1994 ◽  
Vol 76 (5) ◽  
pp. 2070-2075 ◽  
Author(s):  
S. S. Margulies ◽  
G. T. Lei ◽  
G. A. Farkas ◽  
J. R. Rodarte
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Element Model ◽  
Biaxial Stress ◽  
Principal Stresses ◽  
Element Analysis ◽  
Transdiaphragmatic Pressure ◽  
Sigma 1

Stress in the diaphragm, transdiaphragmatic pressure, and diaphragm shape are interrelated by a balance of forces. Using precise in vivo measurements of diaphragm shape and transdiaphragmatic pressure distribution in combination with finite-element analysis (ANSYS), we determined the direction and magnitude of stress in the passive diaphragm at relaxation volume. Lead spheres sutured along muscle bundles identified muscle bundle location and orientation in vivo. The x, y, and z coordinates of the lead spheres and entire surface of the diaphragm, excluding the zone of apposition, were determined to within 1.4 mm. Thin shell elements were used to construct a finite-element model of the diaphragm with a 2.1- to 4.2-mm internodal spacing. The diaphragm was assumed to have a uniform thickness of 2.5 mm, and magnitude and direction of the principal stresses were computed. The results show that 1) diaphragm stress is nonuniform and anisotropic (i.e., varies both with location on diaphragm surface and direction examined), 2) largest stress (sigma 1) is aligned with muscle bundles and is two to four times larger than sigma 2 (perpendicular to sigma 1 in diaphragm plane), and 3) stress along the muscle bundles is larger in vivo under conditions of biaxial stress than at same length in vitro under uniaxial stress. Although diaphragm stress and tension have often been assumed to be uniform, our finding that stress is oriented primarily along the muscle fibers should be considered in future models of the diaphragm.(ABSTRACT TRUNCATED AT 250 WORDS)

On the Bio-Mechanical Properties of a Dual-Porous Osteochondral Scaffold

2008 ◽  
Author(s):  
Hajar Sharif ◽  
Yaser Shanjani ◽  
Mihaela Vlasea ◽  
Ehsan Toyserkani
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Porous Scaffold ◽  
Element Model ◽  
Homogeneous Distribution ◽  
Porous Scaffolds ◽  
Osteochondral Scaffold ◽  
Apparent Stiffness

This work is concerned with the finite element modeling of a dual-porous scaffold including both fine and coarse pores. The layer with coarse pores is suitable for bone in vivo ingrowth and the finer pore layer is appropriate for in vitro cartilage culturing. Such scaffolds can be extensively used for repairing of osteochondral defects. The bio-mechanical properties of the proposed scaffold, including apparent stiffness and strain-based capability of the cell ingrowth, are identified using a 3D Finite Element Model. Moreover, to study the effect of the second layer on the strength of the whole scaffold, the stiffness of the dual and single-porous scaffolds was compared. The result of this study shows that the stiffness decreases by adding the second layer to a single-porous scaffold. Additionally, principal strain histograms of the single and the dual-porous scaffolds are compared to assess the effect of added layer on the capability for cell ingrowth stimulation of the whole structure. According to the results, the dual-porous scaffold provides more homogeneous distribution but a smaller amount of micro-strains which may cause different cell-growth behavior.

Effect of liner material and explosive type on penetration effectiveness of shaped charge

2018 ◽  
Vol 233 (7) ◽  
pp. 1375-1383
Author(s):  
S Zaki ◽  
Emad Uddin ◽  
B Rashid ◽  
A Mubashar ◽  
Samiur R Shah
Keyword(s):  
Finite Element ◽  
Numerical Model ◽  
Element Model ◽  
Shaped Charge ◽  
Jet Formation ◽  
Liner Material ◽  
Numerical Finite Element ◽  
Underlying Mechanisms ◽  
Shaped Charge Jet ◽  
The Given

Shaped charges are used in many civilian and military applications. This study focuses on the effects of liner material and the type of explosive on the development of shaped charge jet. This was carried out by experimentation and numerical finite element-based modelling. Shaped charges were tested on a steel plate during the experimentation and the experimental data were used to validate the developed numerical model of the shaped charge. A hydrocode-based finite element model was able to predict the perforation and jet formation for the shaped charge, as well as the characteristics of the holes formed in the target plate. Several variations of the numerical model with the change of liner material and the filled explosive showed that the higher explosive resulted in higher velocity jet. The jet formation and velocity of jet were compared to determine the better performing combination of the material and explosive for the given shaped charge geometry. The underlying mechanisms were discussed in detail and compared with the previous studies.

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.

Hemostatic wound dressings: Predicting their effects by in vitro tests

2019 ◽  
Vol 33 (9) ◽  
pp. 1285-1297 ◽  
Author(s):  
Cornelia Wiegand ◽  
Martin Abel ◽  
Uta-Christina Hipler ◽  
Peter Elsner ◽  
Michael Zieger ◽  
...  
Keyword(s):  
Blood Clot ◽  
Wound Dressings ◽  
In Vitro Tests ◽  
Regenerated Cellulose ◽  
Oxidized Regenerated Cellulose ◽  
Inflammatory Reactions ◽  
In Vitro Techniques ◽  
Cotton Gauze

Background Application of controlled in vitro techniques can be used as a screening tool for the development of new hemostatic agents allowing quantitative assessment of overall hemostatic potential. Materials and methods Several tests were selected to evaluate the efficacy of cotton gauze, collagen, and oxidized regenerated cellulose for enhancing blood clotting, coagulation, and platelet activation. Results Visual inspection of dressings after blood contact proved the formation of blood clots. Scanning electron microscopy demonstrated the adsorption of blood cells and plasma proteins. Significantly enhanced blood clot formation was observed for collagen together with β-thromboglobulin increase and platelet count reduction. Oxidized regenerated cellulose demonstrated slower clotting rates not yielding any thrombin generation; yet, led to significantly increased thrombin-anti-thrombin-III complex levels compared to the other dressings. As hemostyptica ought to function without triggering any adverse events, induction of hemolysis, instigation of inflammatory reactions, and initiation of the innate complement system were also tested. Here, cotton gauze provoked high PMN elastase and elevated SC5b-9 concentrations. Conclusions A range of tests for desired and undesired effects of materials need to be combined to gain some degree of predictability of the in vivo situation. Collagen-based dressings demonstrated the highest hemostyptic properties with lowest adverse reactions whereas gauze did not induce high coagulation activation but rather activated leukocytes and complement.

Finite Element Analysis of the Distributed Vibration Absorbers for Structural Noise Control

2005 ◽  
Author(s):  
Ashwini Gautam ◽  
Chris Fuller ◽  
James Carneal
Keyword(s):  
Finite Element ◽  
Numerical Model ◽  
Base Plate ◽  
Element Model ◽  
Fe Model ◽  
Vibration Absorbers ◽  
Element Analysis ◽  
Poroelastic Media ◽  
Hexahedral Elements ◽  
Component Models

This work presents an extensive analysis of the properties of distributed vibration absorbers (DVAs) and their effectiveness in controlling the sound radiation from the base structure. The DVA acts as a distributed mass absorber consisting of a thin metal sheet covering a layer of acoustic foam (porous media) that behaves like a distributed spring-mass-damper system. To assess the effectiveness of these DVAs in controlling the vibration of the base structures (plate) a detailed finite elements model has been developed for the DVA and base plate structure. The foam was modeled as a poroelastic media using 8 node hexahedral elements. The structural (plate) domain was modeled using 16 degree of freedom plate elements. Each of the finite element models have been validated by comparing the numerical results with the available analytical and experimental results. These component models were combined to model the DVA. Preliminary experiments conducted on the DVAs have shown an excellent agreement between the results obtained from the numerical model of the DVA and from the experiments. The component models and the DVA model were then combined into a larger FE model comprised of a base plate with the DVA treatment on its surface. The results from the simulation of this numerical model have shown that there has been a significant reduction in the vibration levels of the base plate due to DVA treatment on it. It has been shown from this work that the inclusion of the DVAs on the base plate reduces their vibration response and therefore the radiated noise. Moreover, the detailed development of the finite element model for the foam has provided us with the capability to analyze the physics behind the behavior of the distributed vibration absorbers (DVAs) and to develop more optimized designs for the same.

scholarly journals Investigation of the Thickness Differential on the Formability of Aluminum Tailor Welded Blanks

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 875
Author(s):  
Jie Wu ◽  
Yuri Hovanski ◽  
Michael Miles
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Numerical Model ◽  
Plastic Strain ◽  
Finite Element Model ◽  
Equivalent Plastic Strain ◽  
Element Model ◽  
Dome Height ◽  
Tailor Welded Blanks ◽  
Simulation Results

A finite element model is proposed to investigate the effect of thickness differential on Limiting Dome Height (LDH) testing of aluminum tailor-welded blanks. The numerical model is validated via comparison of the equivalent plastic strain and displacement distribution between the simulation results and the experimental data. The normalized equivalent plastic strain and normalized LDH values are proposed as a means of quantifying the influence of thickness differential for a variety of different ratios. Increasing thickness differential was found to decrease the normalized equivalent plastic strain and normalized LDH values, this providing an evaluation of blank formability.

scholarly journals Numerical Investigation of Ferrofluid Preparation during In-Vitro Culture of Cancer Therapy for Magnetic Nanoparticle Hyperthermia

Sensors ◽  
2021 ◽  
Vol 21 (16) ◽  
pp. 5545 ◽  
Author(s):  
Izaz Raouf ◽  
Piotr Gas ◽  
Heung Soo Kim
Keyword(s):  
Numerical Model ◽  
Cancer Therapy ◽  
Magnetic Nanoparticle ◽  
Research Work ◽  
Thermal Response ◽  
Linear Response Theory ◽  
Novel Approach ◽  
Magnetic Nanoparticle Hyperthermia

Recently, in-vitro studies of magnetic nanoparticle (MNP) hyperthermia have attracted significant attention because of the severity of this cancer therapy for in-vivo culture. Accurate temperature evaluation is one of the key challenges of MNP hyperthermia. Hence, numerical studies play a crucial role in evaluating the thermal behavior of ferrofluids. As a result, the optimum therapeutic conditions can be achieved. The presented research work aims to develop a comprehensive numerical model that directly correlates the MNP hyperthermia parameters to the thermal response of the in-vitro model using optimization through linear response theory (LRT). For that purpose, the ferrofluid solution is evaluated based on various parameters, and the temperature distribution of the system is estimated in space and time. Consequently, the optimum conditions for the ferrofluid preparation are estimated based on experimental and mathematical findings. The reliability of the presented model is evaluated via the correlation analysis between magnetic and calorimetric methods for the specific loss power (SLP) and intrinsic loss power (ILP) calculations. Besides, the presented numerical model is verified with our experimental setup. In summary, the proposed model offers a novel approach to investigate the thermal diffusion of a non-adiabatic ferrofluid sample intended for MNP hyperthermia in cancer treatment.

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