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International Journal for Numerical Methods in Biomedical Engineering

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https://www.readbyqxmd.com/read/30394696/sampling-strategies-for-approximating-patient-variability-in-population-based-finite-element-studies-of-total-hip-replacement
#1
Dermot O'Rourke, Murk Bottema, Mark Taylor
Total hip replacements must be robust to patient variability for long-term success in the population. The challenge during the design process is evaluating an implant in a diverse population but the computational cost of simulating a population of subject-specific finite element (FE) models is not practical. We examined five strategies to generate representative subsets of subjects from a cohort of 103 implanted hip joint FE models to approximate the variability in output metrics. Comparing to the median and distribution of the 95th percentile composite peak micromotion (CPM) and polar gap in the full cohort (CPM median: 136 μm, interquartile range (IQR): 74 - 230 μm) (Polar Gap median: 467 μm, IQR: 434 - 548 μm), the Anatomic Sampling strategy (12 subjects) achieved the best balance of computational cost and approximation of the output metrics (CPM median: 169 μm, IQR: 78 - 236 μm) (Polar Gap median: 469 μm, IQR: 448 - 537 μm)...
November 5, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30358172/a-computational-model-for-microcirculation-including-fahraeus-lindqvist-effect-plasma-skimming-and-fluid-exchange-with-the-tissue-interstitium
#2
Simone di Gregorio, Luca Possenti, Simone di Gregorio, Fannie Maria Gerosa, Giorgio Raimondi, Giustina Casagrande, Maria Laura Costantino, Paolo Zunino
We present a two phase model for microcirculation that describes the interaction of plasma with red blood cells. The model takes into account of typical effects characterizing the microcirculation, such as the Fahraeus-Lindqvist effect and plasma skimming. Besides these features, the model describes the interaction of capillaries with the surrounding tissue. More precisely, the model accounts for the interaction of capillary transmural flow with the surrounding interstitial pressure. Furthermore, the capillaries are represented as one-dimensional channels with arbitrary, possibly curved configuration...
October 24, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30294902/a-comparison-of-the-influence-of-three-different-lumbar-interbody-fusion-approaches-on-stress-in-the-pedicle-screw-fixation-system-finite-element-static-and-vibration-analyses
#3
Wei Fan, Li-Xin Guo
This study aimed to examine breakage risk of the bilateral pedicle screw (BPS) fixation system under static and vibration loadings after three different types of lumbar interbody fusion surgery. A previously validated intact L1-sacrum finite element model was modified to simulate anterior, posterior, and transforaminal lumbar interbody fusion (ALIF, PLIF, and TLIF, respectively) with BPS fixation system (consisting of pedicle screws and rigid connecting rods) at L4-L5. As a risk parameter for breakage, the von Mises stresses in the pedicle screws and the rods for the ALIF, PLIF, and TLIF models under static loading (flexion, extension, lateral bending, and axial torsion moments) and vibration loading (sinusoidal vertical load) were calculated and compared...
October 7, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30281937/numerical-evaluation-of-nonbonded-piezo-sensor-for-biomedical-diagnostics-using-electromechanical-impedance-technique
#4
Shashank Srivastava, Suresh Bhalla
Directly bonded piezo sensor, conventionally employed in the electromechanical impedance (EMI) technique, although a proven candidate for structural health monitoring, is severely constrained in its application in the biomedical field due to its bonding requirement. In contrast, nonbonded piezo sensor (NBPS) provides a viable platform to assess the condition of human bones, tissues, and other biomedical subjects using the EMI technique without inflicting pain or irritation to the skin. The name NBPS was coined to emphasize that there was no direct bonding between the PZT patch and the live subject; instead, the PZT patch was bonded to a supporting medium, which maintains the mechanical interaction between the PZT patch and the subject...
October 3, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30253447/coupled-agent-based-and-hyperelastic-modelling-of-the-left-ventricle-post-myocardial-infarction
#5
X Zhuan, X Y Luo, H Gao, R W Ogden
Understanding the healing and remodelling processes induced by myocardial infarction (MI) of the heart is important and the mechanical properties of the myocardium post-MI can be indicative for effective treatments aimed at avoiding eventual heart failure. MI remodelling is a multiscale feedback process between the mechanical loading and cellular adaptation. In this paper, we use an agent-based model to describe collagen remodelling by fibroblasts regulated by chemical and mechanical cues after acute MI, and upscale into a finite element 3D left ventricular model...
September 25, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30242981/reconstruction-of-vocal-tract-geometries-from-biomechanical-simulations
#6
Saeed Dabbaghchian, Marc Arnela, Olov Engwall, Oriol Guasch
Medical imaging techniques are usually utilized to acquire the vocal tract geometry in 3D, which may then be used e.g., for acoustic/fluid simulation. As an alternative, such a geometry may also be acquired from a biomechanical simulation, which allows to alter the anatomy and/or articulation to study a variety of configurations. In a biomechanical model, each physical structure is described by its geometry and its properties (such as mass, stiffness, muscles, etc). In such a model, the vocal tract itself does not have an explicit representation, since it is a cavity rather than a physical structure...
September 22, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30239175/population-based-priors-in-cardiac-model-personalisation-for-consistent-parameter-estimation-in-heterogeneous-databases
#7
Roch Molléro, Xavier Pennec, Hervé Delingette, Nicholas Ayache, Maxime Sermesant
Personalised cardiac models are a virtual representation of the patient heart, with parameter values for which the simulation fits the available clinical measurements. Models usually have a large number of parameters while the available data for a given patient is typically limited to a small set of measurements, thus the parameters cannot be estimated uniquely. This is a practical obstacle for clinical applications, where accurate parameter values can be important. Here we explore an original approach based on an algorithm called Iteratively Updated Priors (IUP), in which we perform successive personalisations of a full database through Maximum A Posteriori (MAP) estimation, where the prior probability at an iteration is set from the distribution of personalised parameters in the database at the previous iteration...
September 21, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30226292/fluid-structure-interaction-simulations-of-venous-valves-a-monolithic-ale-method-for-large-structural-displacements
#8
Sara Calandrini, Eugenio Aulisa
Venous valves are bicuspidal valves that ensure that blood in veins only flows back to the heart. To prevent retrograde blood flow, the two intraluminal leaflets meet in the center of the vein and occlude the vessel. In fluid-structure interaction (FSI) simulations of venous valves, the large structural displacements may lead to mesh deteriorations and entanglements, causing instabilities of the solver and, consequently, the numerical solution to diverge. In this paper, we propose an arbitrary Lagrangian-Eulerian (ALE) scheme for FSI simulations designed to solve these instabilities...
September 18, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30216704/an-optimized-procedure-to-develop-a-three-dimensional-microfluidic-hydrogel-with-parallel-transport-networks
#9
Mahboubeh Jafarkhani, Zeinab Salehi, Mohammad Ali Shokrgozar, Shohreh Mashayekhan
The development of microfluidic hydrogels is an attractive method to generate continues perfusion, induce vascularization, increase solutes delivery and ultimately improve cell viability. However, the transport processes in many in vitro studies still have not been realized completely. To address this problem, we have developed a micro-channeled hydrogel with different collagen type I concentration of 1, 2 and 3 wt.% and assessed its physical properties and obtained diffusion coefficient of nutrient within the hydrogel...
September 14, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30211982/the-fda-nozzle-benchmark-in-theory-there-is-no-difference-between-theory-and-practice-but-in-practice-there-is
#10
A W Bergersen, M Mortensen, K Valen-Sendstad
The utility of flow simulations relies on the robustness of computational fluid dynamics (CFD) solvers and reproducibility of results. The aim of this study was to validate the Oasis CFD solver against in-vitro experimental measurements of jet breakdown location from the FDA nozzle benchmark at Reynolds number 3500, which is in the particularly-challenging transitional regime. Simulations were performed on meshes consisting of 5, 10, 17 and 28 million (M) tetrahedra, with Δt = 10-5 seconds. The 5 and 10M simulation jets broke down in reasonable agreement with the experiments...
September 13, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30203927/computational-aeroacoustics-to-identify-sound-sources-in-the-generation-of-sibilant-s
#11
Arnau Pont, Oriol Guasch, Joan Baiges, Ramon Codina, Annemie Van Hirtum
A sibilant fricative /s/ is generated when the turbulent jet in the narrow channel between the tongue blade and the hard palate is deflected downwards through the space between the upper and lower incisors, and then impinges the space between the lower incisors and the lower lip. The flow eddies in that region become a source of direct aerodynamic sound, which is also diffracted by the speech articulators and radiated outwards. The numerical simulation of these phenomena is complex. The spectrum of an /s/ typically peaks between 4 - 10 kHz, which implies that very fine computational meshes are needed to capture the eddies producing such high frequencies...
September 11, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30198152/variational-data-assimilation-for-transient-blood-flow-simulations-cerebral-aneurysms-as-an-illustrative-example
#12
S W Funke, M Nordaas, Ø Evju, M S Alnaes, K A Mardal
Several cardiovascular diseases are caused from localised abnormal blood flow such as in the case of stenosis or aneurysms. Prevailing theories propose that the development is caused by abnormal wall-shear stress in focused areas. Computational fluid mechanics have arisen as a promising tool for a more precise and quantitative analysis, in particular because the anatomy is often readily available even by standard imaging techniques such as magnetic resonance and computed tomography angiography. However, computational fluid mechanics rely on accurate initial and boundary conditions which are difficult to obtain...
September 10, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30188608/kinematic-boundary-conditions-substantially-impact-in-silico-ventricular-function
#13
Mathias Peirlinck, Kevin Sack, Pieter De Backer, Pedro Morais, Patrick Segers, Thomas Franz, Matthieu De Beule
No abstract text is available yet for this article.
September 6, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30171673/finite-element-modeling-of-near-wall-mass-transport-in-cardiovascular-flows
#14
Kirk Hansen, Amirhossein Arzani, Shawn Shadden
Many cardiovascular processes involve mass transport between blood and the vessel wall. Finite element methods are commonly used to numerically simulate these processes. Cardiovascular mass transport problems are typically characterized by high Péclet numbers, requiring fine near-wall mesh resolution as well as the use of stabilization techniques to avoid numerical instabilities. In this work, we develop a set of guidelines for solving high-Péclet-number near-wall mass transport problems using the finite element method...
September 1, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30161296/reducing-stress-concentration-on-the-cup-rim-of-hip-implants-under-edge-loading
#15
Mohammad Sharif Uddin, Gi Wing Constance Chan
High stress concentration under edge loading on the cup rim contact due to micro-separation causes accelerated striping wear, fracture, and fatigue in hip implant components. While continuous effort is devoted into improving bearing design and surgical procedure to tackle the problem, the concern still has remained forcing biomedical engineers to seek for new and alternative solutions. The current paper aims to investigate the effect of a new geometry "spline" introduced at the cup's rim corner to minimise stress concentration under edge loading...
August 30, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30152120/a-comparative-study-of-porous-medium-cfd-models-for-flow-diverter-stents-advantages-and-short-comings
#16
Nicolás Dazeo, Javier Dottori, Gustavo Boroni, Ignacio Larrabide
In Computational Fluid Dynamics, there is a high interest in modeling flow diverter stents as porous media due to its reduced computational loads. One of the main difficulties of such models is proper parameter setup. Most authors assume flow diverter's wire screen as an isotropic and homogeneous medium, while others proposes anisotropic configurations, yet very little is discussed about the effect of these assumptions on model's accuracy. In this paper, we compare the effect of different models on hemodynamics in relation to their parameters...
August 27, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30151998/assessment-of-wall-stresses-and-mechanical-heart-power-in-the-left-ventricle-finite-element-modeling-versus-laplace-analysis
#17
Matthias A F Gsell, Christoph M Augustin, Anton J Prassl, Elias Karabelas, Joao F Fernandes, Marcus Kelm, Leonid Goubergrits, Titus Kuehne, Gernot Plank
INTRODUCTION: Stenotic aortic valve disease (AS) causes pressure overload of the left ventricle (LV) that may trigger adverse remodeling and precipitate progression towards heart failure (HF). As myocardial energetics can be impaired during AS, LV wall stresses and biomechanical power provide a complementary view of LV performance that may aide in better assessing the state of disease. OBJECTIVES: Using a high-resolution electro-mechanical (EM) in silico model of the LV as a reference, we evaluated clinically feasible Laplace-based methods for assessing global LV wall stresses and biomechanical power...
August 27, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30133180/a-noninvasive-method-for-the-determination-of-in-vivo-mitral-valve-leaflet-strains
#18
Bruno V Rego, Amir H Khalighi, Andrew Drach, Eric K Lai, Alison M Pouch, Robert C Gorman, Joseph H Gorman, Michael S Sacks
Assessment of mitral valve (MV) function is important in many diagnostic, prognostic, and surgical planning applications for treatment of MV disease. Yet, to date, there are no accepted noninvasive methods for determination of MV leaflet deformation, which is a critical metric of MV function. In this study, we present a novel, completely noninvasive computational method to estimate MV leaflet in-plane strains from clinical-quality real-time three-dimensional echocardiography (rt-3DE) images. The images were first segmented to produce meshed medial-surface leaflet geometries of the open and closed states...
August 21, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30133172/fully-coupled-numerical-model-of-actin-treadmilling-in-the-lamellipodium-of-the-cell
#19
Kiran S Kollepara, Paris D Mulye, Pablo Saez
Cells rely on an interplay of subcellular elements for motility and migration. Certain regions of motile cells, such as the lamellipodium, are made of a complex mixture of actin monomers and filaments, which polymerize at the front of the cell, close to the cell membrane, and depolymerize at the rear. The dynamic actin turnover induces the so-called intracellular retrograde flow, and it is a fundamental process for cell motility. Apart from some comprehensive mathematical models, the computational modelling of actin treadmilling has been based on simpler biophysical models...
August 21, 2018: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/30133165/a-novel-method-to-generate-dynamic-boundary-conditions-for-airway-cfd-by-mapping-upper-airway-movement-with-non-rigid-registration-of-dynamic-and-static-mri
#20
Alister J Bates, Andreas Schuh, Keith McConnell, Brynne M Williams, J Matthew Lanier, Matthew M Willmering, Jason C Woods, Robert J Fleck, Charles L Dumoulin, Raouf S Amin
Computational fluid dynamics (CFD) simulations of airflow in the human airways have the potential to provide a great deal of information that can aid clinicians in case management and surgical decision making, such as airway resistance, energy expenditure, airflow distribution, heat and moisture transfer, and particle deposition, as well as the change in each of these due to surgical interventions. However, the clinical relevance of CFD simulations has been limited to date, as previous models either did not incorporate neuromuscular motion or any motion at all...
August 21, 2018: International Journal for Numerical Methods in Biomedical Engineering
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