Mass-Spring vs. Finite Element Models of Anisotropic Heart Valves: Speed and Accuracy

2010 ◽  
Author(s):  
Peter E. Hammer ◽  
Michael S. Sacks ◽  
Pedro J. del Nido ◽  
Robert D. Howe
Keyword(s):  
Finite Element ◽  
Surgical Planning ◽  
Heart Valves ◽  
Computational Models ◽  
Planning System ◽  
Valve Repair ◽  
Fe Method ◽  
Deformable Bodies ◽  
Mass Spring ◽  
Speed And Accuracy

Heat valve dysfunction can lead to heart failure and death, and surgery is the standard treatment. Valve repair surgery is performed under cardiopulmonary bypass making it difficult for the surgeon to know if a surgical modification will be effective when blood flow is restored. A surgical planning system has been proposed to improve surgical outcomes by allowing a surgeon to explore valve repair strategies on a computer model of a patient’s valve (1). Many groups have published computational models of heart valves based on the finite element (FE) method, but they are prohibitively slow for simulating valve mechanics in an interactive setting. Mass-spring (MS) networks have been used as an alternative to FE methods for modeling deformable bodies, trading off accuracy for speed.

scholarly journals Fast image-based model of mitral valve closure for surgical planning

2008 ◽  
Author(s):  
Peter Hammer ◽  
Nikolay Vasilyev ◽  
Douglas Perrin ◽  
Pedro del Nido ◽  
Robert Howe
Keyword(s):  
Mitral Valve ◽  
Surgical Planning ◽  
Equations Of Motion ◽  
Planning System ◽  
Patient Specific ◽  
Valve Closure ◽  
Spring Model ◽  
Closed State ◽  
Mass Spring Model ◽  
Mass Spring

Surgical repair of the mitral valve results in better outcomes than valve replacement, yet diseased valves are often replaced due to the technical difficulty of the repair process. A surgical planning system based on patient-specific medical images that allows surgeons to simulate and compare potential repair strategies could greatly improve surgical outcomes. The system must simulate valve closure quickly and handle the complex boundary conditions imposed by the chords that tether the valve leaflets. We have developed a process for generating a triangulated mesh of the valve surface from volumetric image data of the opened valve. The closed position of the mesh is then computed using a mass-spring model of dynamics. In the mass-spring model, triangle sides are treated as linear springs supporting only tension. Chords are also treated as linear springs, and self-collisions are detected and handled inelastically. The equations of motion are solved using implicit numerical integration. The simulated closed state is compared with an image of the same valve taken in the closed state to assess accuracy of the model. The model exhibits rapid valve closure and is able to predict the closed state of the valve with reasonable accuracy.

scholarly journals Computational corneal biomechanics in the clinic

2018 ◽  
Vol 2 (2) ◽  
pp. 42-46
Author(s):  
Miguel Ángel Ariza-Gracia ◽  
David Pablo Piñero Llorens ◽  
José Félix Rodríguez Matas ◽  
Begoña Calvo Calzada
Keyword(s):  
Finite Element ◽  
Clinical Assessment ◽  
Surgical Planning ◽  
Computational Models ◽  
A Priori ◽  
Finite Element Simulations ◽  
Corneal Biomechanics ◽  
Patient Specific ◽  
Single Experiment ◽  
Maximum Deformation

Corneal topographers and air-puff devices aim at completely characterizing so-called corneal biomechanics, a collection of features that describes corneal behavior. The European FP7 project (PopCorn) was born with the goal of integrating both technologies. Among the novelties, computational models were included as an integral part of the clinical assessment. Automatic patient-specific (P-S) reconstruction of the cornea, alongside material prediction based on finite element simulations, optimization, and fitting were used to strive forward in a priori surgical planning. Both methodologies show good performance in retrieving the P-S geometry of the cornea (error < 1%) and the maximum deformation amplitude of a non-contact tonometry (error ~ 5%). Nevertheless, physiological and non-physiological corneas cannot be classified solely in terms of material, at least with a single experiment. Eventually, and due to the interplay of different factors (geometry, material, and pressure), results coming from air-puff devices should be handled with care.

scholarly journals A detailed analysis of anatomical plausibility of crossed and uncrossed streamline rendition of the dentato-rubro-thalamic tract (DRT(T)) in a commercial stereotactic planning system

2021 ◽  
Author(s):  
Volker A. Coenen ◽  
Bastian E. Sajonz ◽  
Peter C. Reinacher ◽  
Christoph P. Kaller ◽  
Horst Urbach ◽  
...  
Keyword(s):  
Surgical Planning ◽  
Ground Truth ◽  
Planning System ◽  
Single Subject ◽  
Fiber Structure ◽  
Native Space ◽  
Volume Of Interest ◽  
Mri Scans ◽  
Magnetic Resonance Imaging Mri ◽  
The Individual

Abstract Background An increasing number of neurosurgeons use display of the dentato-rubro-thalamic tract (DRT) based on diffusion weighted imaging (dMRI) as basis for their routine planning of stimulation or lesioning approaches in stereotactic tremor surgery. An evaluation of the anatomical validity of the display of the DRT with respect to modern stereotactic planning systems and across different tracking environments has not been performed. Methods Distinct dMRI and anatomical magnetic resonance imaging (MRI) data of high and low quality from 9 subjects were used. Six subjects had repeated MRI scans and therefore entered the analysis twice. Standardized DICOM structure templates for volume of interest definition were applied in native space for all investigations. For tracking BrainLab Elements (BrainLab, Munich, Germany), two tensor deterministic tracking (FT2), MRtrix IFOD2 (https://www.mrtrix.org), and a global tracking (GT) approach were used to compare the display of the uncrossed (DRTu) and crossed (DRTx) fiber structure after transformation into MNI space. The resulting streamlines were investigated for congruence, reproducibility, anatomical validity, and penetration of anatomical way point structures. Results In general, the DRTu can be depicted with good quality (as judged by waypoints). FT2 (surgical) and GT (neuroscientific) show high congruence. While GT shows partly reproducible results for DRTx, the crossed pathway cannot be reliably reconstructed with the other (iFOD2 and FT2) algorithms. Conclusion Since a direct anatomical comparison is difficult in the individual subjects, we chose a comparison with two research tracking environments as the best possible “ground truth.” FT2 is useful especially because of its manual editing possibilities of cutting erroneous fibers on the single subject level. An uncertainty of 2 mm as mean displacement of DRTu is expectable and should be respected when using this approach for surgical planning. Tractographic renditions of the DRTx on the single subject level seem to be still illusive.

Age Dependent and Anisotropic Material Properties of Immature Porcine Sclera

2013 ◽  
Author(s):  
Jami M. Saffioti ◽  
Brittany Coats
Keyword(s):  
Finite Element ◽  
Material Properties ◽  
Anisotropic Material ◽  
Computational Models ◽  
Fe Model ◽  
Ocular Tissues ◽  
Load Bearing ◽  
Anisotropic Properties ◽  
Age Dependent ◽  
Testing Protocols

Current finite element (FE) models of the pediatric eye are based on adult material properties [2,3]. To date, there are no data characterizing the age dependent material properties of ocular tissues. The sclera is a major load bearing tissue and an essential component to most computational models of the eye. In preparation for the development of a pediatric FE model, age-dependent and anisotropic properties of sclera were evaluated in newborn (3–5 days) and toddler (4 weeks) pigs. Data from this study will guide future testing protocols for human pediatric specimens.

Effect of Ramp Angle on the Anti-Loosening Ability of Wedge Self-Locking Nuts Under Vibration

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Jianhua Liu ◽  
Hao Gong ◽  
Xiaoyu Ding
Keyword(s):  
Finite Element ◽  
Numerical Simulations ◽  
Production Technology ◽  
Material Properties ◽  
Threshold Value ◽  
Commercial Production ◽  
Experimental Results ◽  
Fe Method ◽  
Transversal Vibration

Recently, the wedge self-locking nut, a special anti-loosening product, is receiving more attention because of its excellent reliability in preventing loosening failure under vibration conditions. The key characteristic of a wedge self-locking nut is the special wedge ramp at the root of the thread. In this work, the effect of ramp angle on the anti-loosening ability of wedge self-locking nuts was studied systematically based on numerical simulations and experiments. Wedge self-locking nuts with nine ramp angles (10 deg, 15 deg, 20 deg, 25 deg, 30 deg, 35 deg, 40 deg, 45 deg, and 50 deg) were modeled using a finite element (FE) method, and manufactured using commercial production technology. Their anti-loosening abilities under transversal vibration conditions were analyzed based on numerical and experimental results. It was found that there is a threshold value of the initial preload below which the wedge self-locking nuts would lose their anti-loosening ability. This threshold value of initial preload was then proposed for use as a criterion to evaluate the anti-loosening ability of wedge self-locking nuts quantitatively and to determine the optimal ramp angle. Based on this criterion, it was demonstrated, numerically and experimentally, that a 30 deg wedge ramp resulted in the best anti-loosening ability among nine ramp angles studied. The significance of this study is that it provides an effective method to evaluate the anti-loosening ability of wedge self-locking nuts quantitatively, and determined the optimal ramp angle in terms of anti-loosening ability. The proposed method can also be used to optimize other parameters, such as the material properties and other dimensions, to guarantee the best anti-loosening ability of wedge self-locking nuts.

Prediction of healing efficiency of carbon-based nanocomposites under modified environment

2018 ◽  
Vol 32 (19) ◽  
pp. 1840051 ◽  
Author(s):  
Sung-Min Yoon ◽  
Yun-Hae Kim
Keyword(s):  
Finite Element ◽  
Fe Method ◽  
Interface Elements ◽  
Healing Efficiency ◽  
Crack Faces ◽  
Geometrical Relationship ◽  
Geometrical Equation ◽  
Carbon Based

This study investigates an analysis of the healing behavior of carbon-based nanocomposites by using the finite element (FE) method and provides the quantitative healing values based on the efficiency with respect to the volume, C[Formula: see text]V[Formula: see text]/V[Formula: see text]. An approximation of the geometrical relationship on the profile was considered, and the results compared with the model were used to estimate the healing efficiency based on the initial open profiles. In this model, it contains the interface elements between damaged crack faces. We adjust their sizes and stiffness of elements to compare the profiles with a geometrical equation. We propose that the results of their efficiencies can be compared with the strength of the healing elements that depend on the size of healed volume by the approximation.

scholarly journals Finite Element Analysis to Study Percutaneous Heart Valves

10.5772/38701 ◽  
2012 ◽  
Author(s):  
Silvia Schievano ◽  
Claudio Capelli ◽  
Daria Cosentino ◽  
Giorgia Bosi ◽  
Andrew Taylor
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Heart Valves ◽  
Element Analysis

scholarly journals Aspects of Uncertainty Analysis for Large Nonlinear Computational Models

2010 ◽  
Vol 24-25 ◽  
pp. 25-41 ◽  
Author(s):  
Keith Worden ◽  
W.E. Becker ◽  
Manuela Battipede ◽  
Cecilia Surace
Keyword(s):  
Finite Element ◽  
Monte Carlo ◽  
Computational Models ◽  
Element Model ◽  
Finite Element Models ◽  
Bayesian Algorithm ◽  
Basic Principles ◽  
Structure Interaction ◽  
Output Uncertainty ◽  
Input Uncertainties

This paper concerns the analysis of how uncertainty propagates through large computational models like finite element models. If a model is expensive to run, a Monte Carlo approach based on sampling over the possible model inputs will not be feasible, because the large number of model runs will be prohibitively expensive. Fortunately, an alternative to Monte Carlo is available in the form of the established Bayesian algorithm discussed here; this algorithm can provide information about uncertainty with many less model runs than Monte Carlo requires. The algorithm also provides information regarding sensitivity to the inputs i.e. the extent to which input uncertainties are responsible for output uncertainty. After describing the basic principles of the Bayesian approach, it is illustrated via two case studies: the first concerns a finite element model of a human heart valve and the second, an airship model incorporating fluid structure interaction.

AN ALGORITHM TO CALCULATE THE COMPONENTS OF ALL MUSCLE FORCES DURING EACH PHASES OF THE GAIT CYCLE, FOR THE PELVIC-FEMUR COMPLEX

2005 ◽  
Vol 05 (04) ◽  
pp. 539-548 ◽  
Author(s):  
SANTANU MAJUMDER ◽  
AMIT ROYCHOWDHURY ◽  
SUBRATA PAL
Keyword(s):  
Finite Element ◽  
Hip Joint ◽  
Computational Models ◽  
Gait Cycle ◽  
Muscle Force ◽  
Fe Analysis ◽  
Muscle Forces ◽  
Force Magnitude ◽  
Flexion Extension ◽  
Force Components

With the help of finite element (FE) computational models of femur, pelvis or hip joint to perform quasi-static stress analysis during the entire gait cycle, muscle force components (X, Y, Z) acting on the hip joint and pelvis are to be known. Most of the investigators have presented only the net muscle force magnitude during gait. However, for the FE software, either muscle force components (X, Y, Z) or three angles for the muscle line of action are required as input. No published algorithm (with flowchart) is readily available to calculate the required muscle force components for FE analysis. As the femur rotates about the hip center during gait, the lines of action for 27 muscle forces are also variable. To find out the variable lines of action and muscle force components (X, Y, Z) with directions, an algorithm was developed and presented here with detailed flowchart. We considered the varying angles of adduction/abduction, flexion/extension during gait. This computer program, obtainable from the first author, is able to calculate the muscle force components (X, Y, Z) as output, if the net magnitude of muscle force, hip joint orientations during gait and muscle origin and insertion coordinates are provided as input.

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