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International Journal for Numerical Methods in Biomedical Engineering

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https://www.readbyqxmd.com/read/28906592/influence-of-bronchial-diameter-change-on-the-airflow-dynamics-based-on-a-pressure-controlled-ventilation-system
#1
Shuai Ren, Maolin Cai, Yan Shi, Weiqing Xu, Xiaohua Douglas Zhang
Bronchial diameter is a key parameter that affects the respiratory treatment of mechanically ventilated patients. In this paper, to reveal the influence of bronchial diameter on the airflow dynamics of pressure-controlled mechanically ventilated patients, a new respiratory system model is presented which combines multi-generation airways with lungs. Furthermore, experiments and simulation studies to verify the model are performed. Finally, through the simulation study, it can be determined that in airway generations 2 to 7, when the diameter is reduced to half of the original value, the maximum air pressure (maximum air pressure in lungs) decreases by nearly 16%, the maximum flow decreases by nearly 30%, and the total airway pressure loss (sum of each generation pressure drop) is more than 5 times the original value...
September 14, 2017: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/28898926/hybrid-cell-centred-vertex-model-for-multicellular-systems-with-equilibrium-preserving-remodelling
#2
P Mosaffa, A Rodríguez-Ferran, J J Muñoz
We present a hybrid vertex/cell-centred model for mechanically simulating planar cellular monolayers undergoing cell reorganisation. Cell centres are represented by a triangular nodal network, while the cell boundaries are formed by an associated vertex network. The two networks are coupled through a kinematic constraint which we allow to relax progressively. Special attention is paid to the change of cell-cell connectivity due to cell reorganisation or remodelling events. We handle these situations by using a variable resting length and applying an Equilibrium-Preserving Mapping (EPM) on the new connectivity, which computes a new set of resting lengths that preserve nodal and vertex equilibrium...
September 12, 2017: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/28898561/haptic-simulation-of-tissue-tearing-during-surgery
#3
C Quesada, I Alfaro, D González, F Chinesta, E Cueto
We present a method for the real-time, interactive simulation of tissue tearing during laparoscopic surgery. The method is designed to work at haptic feedback rates (i.e., around 1kHz). Tissue tearing is simulated under the general framework of continuum damage mechanics. The problem is stated as a general, multidimensional parametric problem, which is solved by means of Proper Generalized Decomposition (PGD) methods. One of the main novelties is the reduction of history-dependent problems, such as damage mechanics, by resorting to an approach in which a reduced-order field of initial damage values is considered as a parameter of the formulation...
September 12, 2017: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/28886617/viscous-effects-in-pelvic-floor-muscles-during-childbirth-a-numerical-study
#4
M C P Vila Pouca, J P S Ferreira, D A Oliveira, M P L Parente, R M Natal Jorge
During vaginal delivery women sustain stretching of their pelvic floor, risking tissue injury and adverse outcomes. Realistic numerical simulations of childbirth can help in the understanding of the pelvic floor mechanics and on the prevention of related disorders. In previous studies, biomechanical finite element simulations of a vaginal delivery have been performed disregarding the viscous effects present on all biological soft tissues. The inclusion of the viscoelastic behaviour is fundamental, since it allows to investigate rate-dependent responses...
September 8, 2017: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/28884520/relative-pressure-estimation-from-velocity-measurements-in-blood-flows-state-of-the-art-and-new-approaches
#5
Cristóbal Bertoglio, Rodolfo Núñez, Felipe Galarce, David Nordsletten, Axel Osses
The relative pressure difference across stenotic blood vessels serves as an important clinical index for the diagnosis of many cardiovascular diseases. While the clinical gold standard for relative pressure difference measurements is invasive catheterization, Phase-Contrast Magnetic Resonance Imaging has emerged as a promising tool for enabling a non-invasive quantification, by linking highly spatially resolved velocity measurements with relative pressures via the incompressible Navier-Stokes equations. In this work we provide a review and analysis of current methods for relative pressure estimation and propose three additional techniques...
September 7, 2017: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/28859253/flow-features-and-device-induced-blood-trauma-in-cf-vads-under-a-pulsatile-blood-flow-condition-a-cfd-comparative-study
#6
Zengsheng Chen, Sofen K Jena, Guruprasad A Giridharan, Steven C Koenig, Mark S Slaughter, Bartley P Griffith, Zhongjun J Wu
In this study, the flow features and device-associated blood trauma in four clinical ventricular assist devices (VADs) (two implantable axial VADs, one implantable centrifugal VAD, and one extracorporeal VAD) were computationally analyzed under clinically relevant pulsatile flow conditions. The four VADs were operated at fixed pump speed at a mean rate of 4.5 L/min. Mean pressure difference, wall shear stress (WSS), volume distribution of scalar shear stress (SSS), and shear-induced hemolysis index (HI) were derived from the flow field of each VAD and were compared...
August 31, 2017: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/28796436/the-impact-of-personalized-probabilistic-wall-thickness-models-on-peak-wall-stress-in-abdominal-aortic-aneurysms
#7
J Biehler, W A Wall
If computational models are ever to be used in high stakes decision making in clinical practice, the use of personalized models and predictive simulation techniques is a must. This entails rigorous quantification of uncertainties as well as harnessing available patient-specific data to the greatest extent possible. Although researcher are beginning to realize that taking uncertainty in model input parameters into account is a necessity, the predominantly used probabilistic description for these uncertain parameters are based on elementary random variable models...
August 10, 2017: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/28776326/a-comprehensive-pipeline-for-multi-resolution-modeling-of-the-mitral-valve-validation-computational-efficiency-and-predictive-capability
#8
Andrew Drach, Amir H Khalighi, Michael S Sacks
Multiple studies have demonstrated that the pathological geometries unique to each patient can affect the durability of mitral valve (MV) repairs. While computational modeling of the MV is a promising approach to improve the surgical outcomes, the complex MV geometry precludes use of simplified models. Moreover, the lack of complete in-vivo geometric information presents significant challenges in the development of patient-specific computational models. There is thus a need to determine the level of detail necessary for predictive MV models...
August 3, 2017: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/28755437/phase-contrast-cell-detection-using-multi-level-classification
#9
Ehab Essa, Xianghua Xie
In this paper, we propose a fully automated learning based approach for detecting cells in time-lapse phase contrast images. The proposed system combines two machine learning approaches to achieve bottom-up image segmentation. We apply pixel-wise classification using random forests (RF) classifiers to determine the potential location of the cells. Each pixel is classified into four categories (cell, mitotic cell, halo effect, and background noise). Various image features are extracted at different scales to train the RF classifier...
July 28, 2017: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/28753220/a-novel-method-for-rapid-and-quantitative-mechanical-assessment-of-soft-tissue-for-diagnostic-purposes-a-computational-study
#10
Javier Palacio-Torralba, Daniel W Good, Grant D Stewart, S Alan McNeill, Robert L Reuben, Yuhang Chen
Biological tissues often experience drastic changes in their microstructure due to their pathophysiological conditions. Such microstructural changes could result in variations in mechanical properties, which can be used in diagnosing or monitoring a wide range of diseases, most notably cancer. This paves the avenue for non-invasive diagnosis by instrumented palpation although challenges remain in quantitatively assessing the amount of diseased tissue by means of mechanical characterization. This paper presents a framework for tissue diagnosis using a quantitative and efficient estimation of the fractions of cancerous and non-cancerous tissue without a priori knowledge of tissue microstructure...
July 28, 2017: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/28749579/a-new-type-of-neurons-for-machine-learning
#11
Fenglei Fan, Wenxiang Cong, Ge Wang
In machine learning, an artificial neural network is the mainstream approach. Such a network consists of many neurons. These neurons are of the same type characterized by the 2 features: (1) an inner product of an input vector and a matching weighting vector of trainable parameters and (2) a nonlinear excitation function. Here, we investigate the possibility of replacing the inner product with a quadratic function of the input vector, thereby upgrading the first-order neuron to the second-order neuron, empowering individual neurons and facilitating the optimization of neural networks...
July 27, 2017: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/28744968/benchmark-problems-for-numerical-treatment-of-backflow-at-open-boundaries
#12
C Bertoglio, A Caiazzo, Y Bazilevs, M Braack, M Esmaily, V Gravemeier, A Marsden, O Pironneau, I E Vignon-Clementel, W A Wall
In computational fluid dynamics, incoming velocity at open boundaries, or backflow, often yields to unphysical instabilities already for moderate Reynolds numbers. Several treatments to overcome these backflow instabilities have been proposed in the literature. However, these approaches have not yet been compared in detail in terms of accuracy in different physiological regimes, in particular due to the difficulty to generate stable reference solutions apart from analytical forms. In this work, we present a set of benchmark problems in order to compare different methods in different backflow regimes (with a full reversal flow and with propagating vortices after a stenosis)...
July 25, 2017: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/28744962/inverse-estimation-of-cardiac-activation-times-via-gradient-based-optimisation
#13
Siri Kallhovd, Mary M Maleckar, Marie E Rognes
Computational modeling may provide a quantitative framework for integrating multi-scale data to gain insight into mechanisms of heart disease, identify and test pharmacological and electrical therapy and interventions, and support clinical decisions. Patient-specific computational cardiac models can help guide such procedures, and cardiac inverse modelling is a promising alternative to adequately personalize these models. Indeed, full cardiac inverse modelling is currently becoming computationally feasible; however, fundamental work to assess the feasibility of emerging techniques is still needed...
July 25, 2017: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/28677268/integration-of-element-specific-persistent-homology-and-machine-learning-for-protein-ligand-binding-affinity-prediction
#14
Zixuan Cang, Guo Wei Wei
Protein-ligand binding is a fundamental biological process that is paramount to many other biological processes, such as signal transduction, metabolic pathways, enzyme construction, cell secretion, gene expression, etc. Accurate prediction of protein-ligand binding affinities is vital to rational drug design and the understanding of protein-ligand binding and binding induced function. Existing binding affinity prediction methods are inundated with geometric detail and involve excessively high dimensions, which undermines their predictive power for massive binding data...
July 5, 2017: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/28636811/performance-evaluation-of-gpu-parallelization-space-time-adaptive-algorithms-and-their-combination-for-simulating-cardiac-electrophysiology
#15
Rafael S Oliveira, Bernardo M Rocha, Denise Burgarelli, Wagner Meira, Christakis Constantinides, Rodrigo Weber Dos Santos
The use of computer models as a tool for the study and understanding of the complex phenomena of cardiac electrophysiology has attained increased importance nowadays. At the same time, the increased complexity of the biophysical processes translates into complex computational and mathematical models. In order to speed up cardiac simulations and to allow more precise and realistic uses, two different techniques have been traditionally exploited: parallel computing and sophisticated numerical methods. In this work, we combine a modern parallel computing technique based on multicore and graphics processing units (GPUs), and a sophisticated numerical method based on a new space-time adaptive algorithm...
June 21, 2017: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/28621037/gingival-morphology-controlled-design-of-the-complete-denture-baseplate
#16
Ning Dai, Xiaoling Yu, Yuchun Sun
A removable complete denture is still the main selection for edentulous patients. Over the last five years, digital technologies for producing complete dentures have rapidly developed. Nevertheless, the design method for the baseplate has become the bottleneck of digital complete denture technology development. In this study, we report a novel method for the generation of aesthetic gingiva and polished surfaces of complete dentures that are driven by the feature curve, which can be conveniently modified using the gingival shape factor...
June 16, 2017: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/28618187/physically-consistent-data-assimilation-method-based-on-feedback-control-for-patient-specific-blood-flow-analysis
#17
Satoshi Ii, Mohd Azrul Hisham Mohd Adib, Yoshiyuki Watanabe, Shigeo Wada
This paper presents a novel data assimilation method for patient-specific blood flow analysis based on feedback control theory called the physically consistent feedback control-based data assimilation (PFC-DA) method. In the PFC-DA method, the signal, which is the residual error term of the velocity when comparing the numerical and reference measurement data, is cast as a source term in a Poisson equation for the scalar potential field that induces flow in a closed system. The pressure values at the inlet and outlet boundaries are recursively calculated by this scalar potential field...
June 15, 2017: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/28614900/computational-method-for-estimating-boundary-of-abdominal-subcutaneous-fat-for-absolute-electrical-impedance-tomography
#18
Tohru F Yamaguchi, Yoshiwo Okamoto
Abdominal fat accumulation is considered an essential indicator of human health. Electrical impedance tomography has considerable potential for abdominal fat imaging because of the low specific conductivity of human body fat. In this paper, we propose a robust reconstruction method for high-fidelity conductivity imaging by abstraction of the abdominal cross section using a relatively small number of parameters. Toward this end, we assume homogeneous conductivity in the abdominal subcutaneous fat area, and characterize its geometrical shape by parameters defined as the ratio of the distance from the center to boundary of subcutaneous fat to the distance from the center to outer boundary in 64 equiangular directions...
June 14, 2017: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/28603939/mesh-free-based-variational-level-set-evolution-for-breast-region-segmentation-and-abnormality-detection-using-mammograms
#19
Kanchan L Kashyap, Manish K Bajpai, Pritee Khanna, George Giakos
Automatic segmentation of abnormal region is a crucial task in computer-aided detection system using mammograms. In this work, an automatic abnormality detection algorithm using mammographic images is proposed. In the preprocessing step, partial differential equation-based variational level set method is used for breast region extraction. The evolution of the level set method is done by applying mesh-free-based radial basis function (RBF). The limitation of mesh-based approach is removed by using mesh-free-based RBF method...
June 11, 2017: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/28600860/estimating-the-accuracy-of-a-reduced-order-model-for-the-calculation-of-fractional-flow-reserve-ffr
#20
Etienne Boileau, Sanjay Pant, Carl Roobottom, Igor Sazonov, Jingjing Deng, Xianghua Xie, Perumal Nithiarasu
Image-based noninvasive fractional flow reserve (FFR) is an emergent approach to determine the functional relevance of coronary stenoses. The present work aimed to determine the feasibility of using a method based on coronary computed tomography angiography (CCTA) and reduced-order models (0D-1D) for the evaluation of coronary stenoses. The reduced-order methodology (cFFRRO ) was kept as simple as possible and did not include pressure drop or stenosis models. The geometry definition was incorporated into the physical model used to solve coronary flow and pressure...
June 9, 2017: International Journal for Numerical Methods in Biomedical Engineering
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