scholarly journals Modeling of Damage Evolution in a Patient-Specific Stenosed Artery upon Stent Deployment

2020 ◽  
Vol 12 (09) ◽  
pp. 2050101
Author(s):  
Fatemeh Rouhani ◽  
Behrooz Fereidoonnezhad ◽  
Mohammad Reza Zakerzadeh ◽  
Mostafa Baghani
Keyword(s):  
Computational Models ◽  
Permanent Deformation ◽  
Constitutive Models ◽  
Element Model ◽  
Patient Specific ◽  
Stent Deployment ◽  
Early Evaluation ◽  
Physiological Loading ◽  
Stenosed Artery ◽  
Arterial Tissue

Computational models provide a powerful tool for pre-clinical assessment of medical devices and early evaluation of potential risks to the patient in terms of plaque fragmentation and in-stent restenosis (ISR). Using a suitable constitutive model for arterial tissue is key for the development of a reliable computational model. Although some inelastic phenomena such as stress softening and permanent deformation likely occur due to the supra-physiological loading of arterial tissue during the stenting procedure, hyperelastic constitutive models have been employed in most of the previously developed computational models. This study presents a finite element model for stent deployment into a patient-specific stenosed artery while inelastic arterial behaviors due to supra-physiological loading of the tissue have been considered. Specifically, the maximum stress in the plaque and the arterial layers which is the main cause of plaque fracture during stent deployment and the surgically-induced injury (damage) in the arterial wall, as the main cause of ISR, are presented. The results are compared with the commonly-used hyperelastic behavior for arterial layers. Furthermore, the effects of arterial material parameter variation, analogues to different patients, are investigated. A higher amount of damage is predicted for the artery which shows a higher stress in a specific strain.

scholarly journals Modeling of damage evolution in a patient-specific stenosed artery upon stent deployment

2020 ◽  
Author(s):  
Fatemeh Rouhani ◽  
Behrooz Fereidoonnezhad ◽  
Mohammad Reza Zakerzadeh ◽  
Mostafa Baghani
Keyword(s):  
Computational Models ◽  
Permanent Deformation ◽  
Constitutive Models ◽  
Element Model ◽  
Patient Specific ◽  
Stent Deployment ◽  
Physiological Loading ◽  
Stenosed Artery ◽  
As Stress ◽  
Stenting Procedure

Although some inelastic phenomena such as stress softening and permanent deformation likely occur due to the supra-physiological loading of arterial tissue during the stenting procedure, hyperelastic constitutive models have been employed in most of the previously developed computational models. This study presents a finite element model for stent deployment into a patient-specific stenosed artery while inelastic arterial behaviors due to supra-physiological loading of the tissue have been considered.

Modeling Grain Boundary Damage Evolution in As-Measured 3D Microstructure

2011 ◽  
Author(s):  
I. Simonovski ◽  
L. Cizelj
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Early Development ◽  
Computational Models ◽  
Complex Geometry ◽  
Steel Wire ◽  
Constitutive Models ◽  
Element Model ◽  
Isotropic Elasticity ◽  
Individual Grains

In recent years we have seen a development of novel experimental techniques that enable one to non-destructively characterize polycrystalline microstructures. These techniques hold significant advantages over approaches like serial sectioning since the specimen is not destroyed in the characterization process. This is of immense value in advancing our understanding of materials and multiscale computational models. In particular, processes at the small length scales like the initiation and early development of grain boundary damage can now be measured more closely while the resulting simulations can now be directly compared to the experimental data. The task is, however, far from being simple as extremely complex geometry needs to be coupled with advance constitutive models for the bulk grain material and the grain boundaries themselves need to be combined. In this work a model, based on a X-ray diffraction contrast tomography data of a stainless steel wire with a diameter of 0.4 mm is presented. 3D topology and crystallographic orientation of individual grains are directly transferred into a finite element model. Grain boundary damage initialization and early development is then explored for a number of cases, ranging from isotropic elasticity up to crystal plasticity constitutive laws for the bulk grain material. In all cases the grain boundaries are modeled using the cohesive zone approach. Also, the stability of the simulations and measures aimed at improving it are reported upon.

scholarly journals Effects of intracorneal ring segments implementation technique and design on corneal biomechanics and keratometry in a personalized computational analysis

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Niksa Mohammadi Bagheri ◽  
Mahmoud Kadkhodaei ◽  
Shiva Pirhadi ◽  
Peiman Mosaddegh
Keyword(s):  
Clinical Data ◽  
Three Dimensional ◽  
Element Model ◽  
Von Mises Stress ◽  
Patient Specific ◽  
Average Error ◽  
Constant Thickness ◽  
Arc Length ◽  
Implementation Techniques ◽  
Von Mises

AbstractThe implementation of intracorneal ring segments (ICRS) is one of the successfully applied refractive operations for the treatment of keratoconus (kc) progression. The different selection of ICRS types along with the surgical implementation techniques can significantly affect surgical outcomes. Thus, this study aimed to investigate the influence of ICRS implementation techniques and design on the postoperative biomechanical state and keratometry results. The clinical data of three patients with different stages and patterns of keratoconus were assessed to develop a three-dimensional (3D) patient-specific finite-element model (FEM) of the keratoconic cornea. For each patient, the exact surgery procedure definitions were interpreted in the step-by-step FEM. Then, seven surgical scenarios, including different ICRS designs (complete and incomplete segment), with two surgical implementation methods (tunnel incision and lamellar pocket cut), were simulated. The pre- and postoperative predicted results of FEM were validated with the corresponding clinical data. For the pre- and postoperative results, the average error of 0.4% and 3.7% for the mean keratometry value ($$\text {K}_{\text{mean}}$$ K mean ) were predicted. Furthermore, the difference in induced flattening effects was negligible for three ICRS types (KeraRing segment with arc-length of 355, 320, and two separate 160) of equal thickness. In contrast, the single and double progressive thickness of KeraRing 160 caused a significantly lower flattening effect compared to the same type with constant thickness. The observations indicated that the greater the segment thickness and arc-length, the lower the induced mean keratometry values. While the application of the tunnel incision method resulted in a lower $$\text {K}_{\text{mean}}$$ K mean value for moderate and advanced KC, the induced maximum Von Mises stress on the postoperative cornea exceeded the induced maximum stress on the cornea more than two to five times compared to the pocket incision and the preoperative state of the cornea. In particular, an asymmetric regional Von Mises stress on the corneal surface was generated with a progressive ICRS thickness. These findings could be an early biomechanical sign for a later corneal instability and ICRS migration. The developed methodology provided a platform to personalize ICRS refractive surgery with regard to the patient’s keratoconus stage in order to facilitate the efficiency and biomechanical stability of the surgery.

scholarly journals Supervised Domain Adaptation for Automated Semantic Segmentation of the Atrial Cavity

Entropy ◽  
2021 ◽  
Vol 23 (7) ◽  
pp. 898
Author(s):  
Marta Saiz-Vivó ◽  
Adrián Colomer ◽  
Carles Fonfría ◽  
Luis Martí-Bonmatí ◽  
Valery Naranjo
Keyword(s):  
High Performance ◽  
Computational Models ◽  
Domain Adaptation ◽  
Semantic Segmentation ◽  
Patient Specific ◽  
Mr Images ◽  
Training Samples ◽  
Volumetric Images ◽  
Acquisition Costs ◽  
Left And Right

Atrial fibrillation (AF) is the most common cardiac arrhythmia. At present, cardiac ablation is the main treatment procedure for AF. To guide and plan this procedure, it is essential for clinicians to obtain patient-specific 3D geometrical models of the atria. For this, there is an interest in automatic image segmentation algorithms, such as deep learning (DL) methods, as opposed to manual segmentation, an error-prone and time-consuming method. However, to optimize DL algorithms, many annotated examples are required, increasing acquisition costs. The aim of this work is to develop automatic and high-performance computational models for left and right atrium (LA and RA) segmentation from a few labelled MRI volumetric images with a 3D Dual U-Net algorithm. For this, a supervised domain adaptation (SDA) method is introduced to infer knowledge from late gadolinium enhanced (LGE) MRI volumetric training samples (80 LA annotated samples) to a network trained with balanced steady-state free precession (bSSFP) MR images of limited number of annotations (19 RA and LA annotated samples). The resulting knowledge-transferred model SDA outperformed the same network trained from scratch in both RA (Dice equals 0.9160) and LA (Dice equals 0.8813) segmentation tasks.

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.

Method for Incorporating Three-Dimensional Residual Stresses Into Patient-Specific Simulations of Arteries

2013 ◽  
Author(s):  
David M. Pierce ◽  
Thomas E. Fastl ◽  
Hannah Weisbecker ◽  
Gerhard A. Holzapfel ◽  
Borja Rodriguez-Vila ◽  
...  
Keyword(s):  
Medical Imaging ◽  
Three Dimensional ◽  
Constitutive Models ◽  
Abdominal Aortic Aneurysms ◽  
Aortic Aneurysms ◽  
Patient Specific ◽  
Abdominal Aortic ◽  
Model Geometry ◽  
Reconstructed Model

Through progress in medical imaging, image analysis and finite element (FE) meshing tools it is now possible to extract patient-specific geometries from medical images of, e.g., abdominal aortic aneurysms (AAAs), and thus to study clinically relevant problems via FE simulations. Medical imaging is most often performed in vivo, and hence the reconstructed model geometry in the problem of interest will represent the in vivo state, e.g., the AAA at physiological blood pressure. However, classical continuum mechanics and FE methods assume that constitutive models and the corresponding simulations start from an unloaded, stress-free reference condition.

scholarly journals How to Validate in silico Deployment of Coronary Stents: Strategies and Limitations in the Choice of Comparator

2021 ◽  
Vol 3 ◽  
Author(s):  
Francesca Berti ◽  
Luca Antonini ◽  
Gianluca Poletti ◽  
Constantino Fiuza ◽  
Ted J. Vaughan ◽  
...  
Keyword(s):  
Numerical Model ◽  
Medical Devices ◽  
In Silico ◽  
Computational Models ◽  
Ad Hoc ◽  
Coronary Stent ◽  
Controlled Environment ◽  
Stent Deployment ◽  
Validation Plan ◽  
3D Printed

This study aims at proposing and discussing useful indications to all those who need to validate a numerical model of coronary stent deployment. The proof of the reliability of a numerical model is becoming of paramount importance in the era of in silico trials. Recently, the ASME V&V Standard Committee for medical devices prepared the V&V 40 standard document that provides a framework that guides users in establishing and assessing the relevance and adequacy of verification and validation activities performed for proving the credibility of models. To the knowledge of the authors, only a few examples of the application of the V&V 40 framework to medical devices are available in the literature, but none about stents. Specifically, in this study, the authors wish to emphasize the choice of a relevant set of experimental activities to provide data for the validation of computational models aiming to predict coronary stent deployment. Attention is focused on the use of ad hoc 3D-printed mock vessels in the validation plan, which could allow evaluating aspects of clinical relevance in a representative but controlled environment.

scholarly journals Biomechanical modeling of knee for specific patients with chronic anterior cruciate ligament injury

2013 ◽  
Vol 10 (1) ◽  
pp. 525-545 ◽  
Author(s):  
Nenad Filipovic ◽  
Velibor Isailovic ◽  
Dalibor Nikolic ◽  
Aleksandar Peulic ◽  
Nikola Mijailovic ◽  
...  
Keyword(s):  
Gait Analysis ◽  
Acl Reconstruction ◽  
Cruciate Ligament ◽  
Biomechanical Model ◽  
Element Model ◽  
Gait Pattern ◽  
Von Mises Stress ◽  
Ligament Injury ◽  
Patient Specific ◽  
Reconstruction Technique

In this study we modeled a patient specific 3D knee after anterior cruicate ligament (ACL) reconstruction. The purpose of the ACL reconstruction is to achieve stability in the entire range of motion of the knee and the establishment of the normal gait pattern. We present a new reconstruction technique that generates patient-specific 3D knee models from patient?s magnetic resonant images (MRIs). The motion of the ACL reconstruction patients is measured by OptiTrack system with six infrared cameras. Finite element model of bones, cartilage and meniscus is used for determination stress and strain distribution at different body postures during gait analysis. It was observed that the maximum effective von Mises stress distribution up to 8 MPa occurred during 30% of the gait cycle on the meniscus. The biomechanical model of the knee joint during gait analysis can provide insight into the underlying mechanisms of knee function after ACL reconstruction.

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