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International Journal for Numerical Methods in Biomedical Engineering

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https://www.readbyqxmd.com/read/27885825/multiphase-fluid-solid-coupled-analysis-of-shock-bubble-stone-interaction-in-shockwave-lithotripsy
#1
K G Wang
A novel multiphase fluid-solid coupled computational framework is applied to investigate the interaction of a kidney stone immersed in liquid with a lithotripsy shock wave (LSW) and a gas bubble near the stone. The main objective is to elucidate the effects of a bubble in the shock path to the elastic and fracture behaviors of the stone. The computational framework couples a finite volume two-phase computational fluid dynamics (CFD) solver with a finite element (FE) computational solid dynamics (CSD) solver...
November 24, 2016: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/27885813/a-novel-modelling-approach-to-energy-transport-in-a-respiratory-system
#2
Perumal Nithiarasu, Igor Sazonov
In this paper, energy transport in a respiratory tract is modelled using the finite element method for the first time. The upper and lower respiratory tracts are approximated as a one-dimensional domain with varying cross sectional and surface areas and the radial heat conduction in the tissue is approximated using the one dimensional cylindrical coordinate system. The governing equations are solved using one-dimensional linear finite elements with convective and evaporative boundary conditions on the wall...
November 24, 2016: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/27883273/a-velocity-tracking-approach-for-the-data-assimilation-problem-in-blood-flow-simulations
#3
J Tiago, T Guerra, A Sequeira
Several advances have been made in Data Assimilation techniques applied to blood flow modeling. Typically, idealized boundary conditions, only verified in straight parts of the vessel, are assumed. We present a general approach, based on a Dirichlet boundary control problem, that may potentially be used in different parts of the arterial system. The relevance of this method appears when computational reconstructions of the 3D domains, prone to be considered sufficiently extended, are either not possible, or desirable, due to computational costs...
November 24, 2016: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/27863152/direct-numerical-simulation-of-transitional-hydrodynamics-of-the-cerebrospinal-fluid-in-chiari-i-malformation-the-role-of-cranio-vertebral-junction
#4
Kartik Jain, Geir Ringstad, Per-Kristian Eide, Kent-André Mardal
Obstruction to the cerebrospinal fluid (CSF) outflow caused by the herniation of cerebellar tonsils as a result of Chiari malformation type I leads to altered CSF hydrodynamics. This contribution explores the minutest characteristics of the CSF hydrodynamics in cervical subarachnoid spaces (SAS) of a healthy subject and two Chiari patients by performing highly resolved direct numerical simulation. The Lattice Boltzmann method is used for the simulations due to its scalability on modern supercomputers that allow us to simulate up to  ∼ 10(9) cells while resolving the Kolmogorov microscales...
November 10, 2016: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/27863131/conditions-of-microvessel-occlusion-for-blood-coagulation-in-flow
#5
A Bouchnita, T Galochkina, P Kurbatova, P Nony, V Volpert
Vessel occlusion is a perturbation of blood flow inside a blood vessel because of the fibrin clot formation. As a result, blood circulation in the vessel can be slowed down or even stopped. This can provoke the risk of cardiovascular events. In order to explore this phenomenon, we used a previously developed mathematical model of blood clotting to describe the concentrations of blood factors with a reaction-diffusion system of equations. The Navier-Stokes equations were used to model blood flow and we treated the clot as a porous medium...
November 10, 2016: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/27863119/adaptive-unified-continuum-fem-modeling-of-a-3d-fsi-benchmark-problem
#6
Johan Jansson, Niyazi Cem Degirmenci, Johan Hoffman
In this paper we address a 3D fluid-structure interaction (FSI) benchmark problem that represents important characteristics of biomedical modeling. We present a goal-oriented adaptive finite element methodology for incompressible FSI based on a streamline-diffusion type stabilization of the balance equations for mass and momentum for the entire continuum in the domain, which is implemented in the Unicorn/FEniCS software framework. A phase marker function and its corresponding transport equation is introduced to select the constitutive law, where the mesh tracks the discontinous fluid-structure interface...
November 10, 2016: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/27863120/numerical-simulation-of-volume-controlled-mechanical-ventilated-respiratory-system-with-two-different-lungs
#7
Yan Shi, Bolun Zhang, Maolin Cai, Xiaohua Douglas Zhang
Mechanical ventilation is a key therapy for patients who can't breathe adequately by themselves, and dynamics of mechanical ventilation system is of great significance for life support of patients. Recently, models of mechanical ventilated respiratory system with one lung are used to simulate respiratory system of patients. However, human has two lungs. When the respiratory characteristics of two lungs are different, single-lung model cannot reflect real respiratory system. In this paper, to illustrate dynamic characteristics of mechanical ventilated respiratory system with two different lungs, we propose a mathematical model of mechanical ventilated respiratory system with two different lungs and conduct experiments to verify the model...
November 9, 2016: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/27813346/validation-of-a-non-conforming-monolithic-fluid-structure-interaction-method-using-phase-contrast-mri
#8
A Hessenthaler, O Röhrle, D A Nordsletten
This paper details the validation of a non-conforming arbitrary Lagrangian-Eulerian fluid-structure interaction (FSI) technique using a recently developed experimental 3D FSI benchmark problem. Numerical experiments for steady and transient test cases of the benchmark were conducted employing an inf-sup stable and a general Galerkin scheme. The performance of both schemes is assessed. Spatial refinement with three mesh refinement levels and fluid domain truncation with two fluid domain lengths are studied as well as employing a sequence of increasing time step sizes for steady-state cases...
November 4, 2016: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/27813272/experiment-for-validation-of-fluid-structure-interaction-models-and-algorithms
#9
A Hessenthaler, N R Gaddum, O Holub, R Sinkus, O Röhrle, D A Nordsletten
In this paper a fluid-structure interaction (FSI) experiment is presented. The aim of this experiment is to provide a challenging yet easy-to-setup FSI test case that addresses the need for rigorous testing of FSI algorithms and modeling frameworks. Steady-state and periodic steady-state test cases with constant and periodic inflow were established. Focus of the experiment is on biomedical engineering applications with flow being in the laminar regime with Reynolds numbers 1283 and 651. Flow and solid domains were defined using CAD tools...
November 4, 2016: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/27860424/aerosol-transport-throughout-inspiration-and-expiration-in-the-pulmonary-airways
#10
Jessica M Oakes, Shawn C Shadden, Céline Grandmont, Irene E Vignon-Clementel
Little is known about transport throughout the respiration cycle in the conducting airways. It is challenging to appropriately describe the time-dependent number of particles entering back into the model during exhalation. Modeling the entire lung is not feasible; therefore multi-domain methods must be employed. Here, we present a new framework that is designed to simulate particles throughout the respiration cycle, incorporating realistic airway geometry and respiration. This framework is applied for a healthy rat lung exposed to  ∼ 1μm diameter particles to facilitate parameterization and validation...
November 2, 2016: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/27796075/an-atlas-and-data-driven-approach-to-initializing-reaction-diffusion-systems-in-computer-cardiac-electrophysiology
#11
Corné Hoogendoorn, Rafael Sebastian, José Félix Rodriguez, Karim Lekadir, Alejandro F Frangi
The cardiac electrophysiology (EP) problem is governed by a nonlinear anisotropic reaction-diffusion system with a very rapidly varying reaction term associated with the transmembrane cell current. The nonlinearity associated with the cell models requires a stabilization process before any simulation is carried out. More importantly, when used in a three-dimensional (3D) anatomy, it is not sufficient to perform this stabilization on the basis of isolated cells only, since the coupling of the different cells through the tissue greatly modulates the dynamics of the system...
October 30, 2016: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/27781402/automated-femoral-landmark-extraction-for-optimal-prosthesis-placement-in-total-hip-arthroplasty
#12
D F Almeida, R B Ruben, J Folgado, P R Fernandes, J Gamelas, B Verhegghe, M De Beule
The automated extraction of anatomical reference landmarks in the femoral volume may improve speed, precision and accuracy of surgical procedures, such as total hip arthroplasty. These landmarks are often hard to achieve, even via surgical incision. In addition, it provides a presurgical guidance for prosthesis sizing and placement. This study presents an automated workflow for femoral orientation and landmark extraction from a 3D surface mesh. The extraction of parameters such as the femoral neck axis, the femoral middle diaphysis axis, both trochanters and the center of the femoral head will allow the surgeon to establish the correct position of bony cuts to restore leg length and femoral offset...
October 25, 2016: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/27781397/assessment-of-reduced-order-unscented-kalman-filter-for-parameter-identification-in-one-dimensional-blood-flow-models-using-experimental-data
#13
A Caiazzo, F Caforio, G Montecinos, L O Muller, P J Blanco, E F Toro
This work presents a detailed investigation of a parameter estimation approach based on the reduced order unscented Kalman filter (ROUKF) in the context of one-dimensional blood flow models. In particular, the main aims of this study are (i) to investigate the effects of using real measurements versus synthetic data for the estimation procedure (i.e., numerical results of the same in silico model, perturbed with noise) and (ii) to identify potential difficulties and limitations of the approach in clinically realistic applications in order to assess the applicability of the filter to such setups...
October 25, 2016: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/27743468/a-monolithic-3d-0d-coupled-closed-loop-model-of-the-heart-and-the-vascular-system-experiment-based-parameter-estimation-for-patient-specific-cardiac-mechanics
#14
M Hirschvogel, M Bassilious, L Jagschies, S M Wildhirt, M W Gee
A model for patient-specific cardiac mechanics simulation is introduced, incorporating a 3-dimensional finite element model of the ventricular part of the heart which is coupled to a reduced-order 0-dimensional closed-loop vascular system, heart valve and atrial chamber model.The ventricles are modeled by a nonlinear orthotropic passive material law. The electrical activation is mimicked by a prescribed parametrized active stress acting along a generic muscle fiber orientation. Our activation function is constructed such that the start of ventricular contraction and relaxation as well as the active stress curve's slope are parameterized...
October 15, 2016: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/27709800/an-implicit-solver-for-1d-arterial-network-models
#15
Jason Carson, Raoul Van Loon
In this study the one dimensional blood flow equations are solved using a newly proposed enhanced trapezoidal rule method ETM, which is an extension to the simplified trapezoidal rule method STM. At vessel junctions the conservation of mass and conservation of total pressure are held as system constraints using Lagrange multipliers that can be physically interpreted as external flow rates. The ETM scheme is compared with published arterial network benchmark problems and a dam break problem. Strengths of the ETM scheme include being simple to implement, intuitive connection to lumped parameter models, and no restrictive stability criteria such as the CFL number...
October 6, 2016: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/27704716/a-quasi-3d-wire-approach-to-model-pulmonary-airflow-in-human-airways
#16
Ravishekar Kannan, Z J Chen, Narender Singh, Andrzej Przekwas, Renishkumar Delvadia, Geng Tian, Ross Walenga
The models used for modeling the airflow in the human airways are either 0-dimensional compartmental or full 3-dimensional (3D) computational fluid dynamics (CFD) models. In the former, airways are treated as compartments, and the computations are performed with several assumptions, thereby generating a low-fidelity solution. The CFD method displays extremely high fidelity since the solution is obtained by solving the conservation equations in a physiologically consistent geometry. However, CFD models (1) require millions of degrees of freedom to accurately describe the geometry and to reduce the discretization errors, (2) have convergence problems, and (3) require several days to simulate a few breathing cycles...
October 5, 2016: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/27704706/computational-design-and-engineering-of-polymeric-orthodontic-aligners
#17
S Barone, A Paoli, A V Razionale, R Savignano
Transparent and removable aligners represent an effective solution to correct various orthodontic malocclusions through minimally invasive procedures. An aligner-based treatment requires patients to sequentially wear dentition-mating shells obtained by thermoforming polymeric disks on reference dental models. An aligner is shaped introducing a geometrical mismatch with respect to the actual tooth positions to induce a loading system, which moves the target teeth toward the correct positions. The common practice is based on selecting the aligner features (material, thickness, and auxiliary elements) by only considering clinician's subjective assessments...
October 5, 2016: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/27696717/non-newtonian-versus-numerical-rheology-practical-impact-of-shear-thinning-on-the-prediction-of-stable-and-unstable-flows-in-intracranial-aneurysms
#18
M O Khan, D A Steinman, K Valen-Sendstad
Computational fluid dynamics (CFD) shows promise for informing treatment planning and rupture risk assessment for intracranial aneurysms. Much attention has been paid to the impact on predicted hemodynamics of various modelling assumptions and uncertainties, including the need for modelling the non-Newtonian, shear-thinning rheology of blood, with equivocal results. Our study clarifies this issue by contextualizing the impact of rheology model against the recently demonstrated impact of CFD solution strategy on the prediction of aneurysm flow instabilities...
October 1, 2016: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/27661463/improved-hybrid-gpu-algorithm-for-solving-cardiac-electrophysiology-problems-on-purkinje-networks
#19
M Lange, S Palamara, T Lassila, C Vergara, A Quarteroni, A F Frangi
Cardiac Purkinje fibers provide an important pathway to the coordinated contraction of the heart. We present a numerical algorithm for the solution of electrophysiology problems across the Purkinje network that is efficient enough to be used in in silico studies on realistic Purkinje networks with physiologically detailed models of ion exchange at the cell membrane. The algorithm is on the basis of operator splitting and is provided with 3 different implementations: pure CPU, hybrid CPU/GPU, and pure GPU. Compared to our previous work, we modify the explicit gap junction term at network bifurcations to improve its mathematical consistency...
September 23, 2016: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/27654010/a-methodology-for-constraining-power-in-finite-element-modeling-of-radiofrequency-ablation
#20
Yansheng Jiang, Ricardo Possebon, Stefaan Mulier, Chong Wang, Feng Chen, Yuanbo Feng, Qian Xia, Yewei Liu, Ting Yin, Raymond Oyen, Yicheng Ni
Radiofrequency ablation (RFA) is a minimally invasive thermal therapy for the treatment of cancer, hyperopia, and cardiac tachyarrhythmia. In RFA, the power delivered to the tissue is a key parameter. The objective of this study was to establish a methodology for the finite element modeling of RFA with constant power. Because of changes in the electric conductivity of tissue with temperature, a nonconventional boundary value problem arises in the mathematic modeling of RFA: neither the voltage (Dirichlet condition) nor the current (Neumann condition), but the power, that is, the product of voltage and current was prescribed on part of boundary...
September 21, 2016: International Journal for Numerical Methods in Biomedical Engineering
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