SIMULATION-BASED DESIGN AND MATERIAL MODELING FOR ENT IMPLANTS

Ph.DDOCTOR OF PHILOSOPH

Numerical Simulation in Biomechanics and Biomedical Engineering

In the first contribution, Morbiducci and co-workers discuss the theoretical and methodological bases supporting the Lagrangian- and Euler-based methods, highlighting their application to cardiovascular flows. The second contribution, by the Ansón and van Lenthe groups, proposes an automated virtual bench test for evaluating the stability of custom shoulder implants without the necessity of mechanical testing. Urdeitx and Doweidar, in the third paper, also adopt the finite element method for developing a computational model aim to study cardiac cell behavior under mechano-electric stimulation. In the fourth contribution, Ayensa-Jiménez et al. develop a methodology to approximate the multidimensional probability density function of the parametric analysis obtained developing a mathematical model of the cancer evolution. The fifth paper is oriented to the topological data analysis; the group of Cueto and Chinesta designs a predictive model capable of estimating the state of drivers using the data collected from motion sensors. In the sixth contribution, the Ohayon and Finet group uses wall shear stress-derived descriptors to study the role of recirculation in the arterial restenosis due to different malapposed and overlapping stent conditions. In the seventh contribution, the research group of Antón demonstrates that the simulation time can be reduced for cardiovascular numerical analysis considering an adequate geometry-reduction strategy applicable to truncated patient specific artery. In the eighth paper, Grasa and Calvo present a numerical model based on the finite element method for simulating extraocular muscle dynamics. The ninth paper, authored by Kahla et al., presents a mathematical mechano-pharmaco-biological model for bone remodeling. Martínez, Peña, and co-workers propose in the tenth paper a methodology to calibrate the dissection properties of aorta layer, with the aim of providing useful information for reliable numerical tools. In the eleventh contribution, Martínez-Bocanegra et al. present the structural behavior of a foot model using a detailed finite element model. The twelfth contribution is centered on the methodology to perform a finite, element-based, numerical model of a hydroxyapatite 3D printed bone scaffold. In the thirteenth paper, Talygin and Gorodkov present analytical expressions describing swirling jets for cardiovascular applications. In the fourteenth contribution, Schenkel and Halliday propose a novel non-Newtonian particle transport model for red blood cells. Finally, Zurita et al. propose a parametric numerical tool for analyzing a silicone customized 3D printable trachea-bronchial prosthesis

VAD in failing Fontan: simulation of ventricular, cavo-pulmonary and biventricular assistance in systolic/diastolic ventricular dysfunction and in pulmonary vascular resistance increase.

Aim: Due to the lack of donors, VADs could be an alternative to heart transplantation for Failing Fontan patients (PTs). Considering the complex physiopathology and the type of VAD connection, a numerical model (NM) could be useful to support clinical decisions. The aim of this work is to test a NM simulating the VADs effects on failing Fontan for systolic dysfunction (SD), diastolic dysfunction (DD) and pulmonary vascular resistance increase (PRI). Methods: Data of 10 Fontan PTs were used to simulate the PTs baseline using a dedicated NM. Then, for each PTs a SD, a DD and a PRI were simulated. Finally, for each PT and for each pathology, the VADs implantation was simulated. Results: NM can well reproduce PTs baseline. In the case of SD, LVAD increases the cardiac output (CO) (35%) and the arterial systemic pressure (ASP) (25%). With cavo-pulmonary assistance (RVAD) a decrease of inferior vena cava pressure (IVCP) (39%) was observed with 34% increase of CO. With the BIVAD an increase of ASP (29%) and CO (37%) was observed. In the case of DD, the LVAD increases CO (42%), the RVAD decreases the IVCP. In the case of PRI, the highest CO (50%) and ASP (28%) increase is obtained with an RVAD together with the highest decrease of IVCP (53%). Conclusions: The use of NM could be helpful in this innovative field to evaluate the VADs implantation effects on specific PT to support PT and VAD selection

Development of 3D-Printed, Drug-Eluting Airway Stents for the Personalised and Local Treatment of Central Airway Pathologies

Airway stents are the most widely used means of palliative treatment for patients suffering from central airway obstruction (CAO). CAO may occur directly from airway stenosis, respiratory cancers, or tracheobronchomalacia, a symptom of weakening airway cartilage. Current airway stents are constructed using medical-grade silicone or nickel-titanium (nitinol) alloy, that have fixed geometry and are inserted via bronchoscopic surgery. These stents have many shortcomings due to their standardised size and dimensions that are not compatible with the patient’s lung anatomy, causing stent migration, granulation tissue growth, and airway secretions. These incidences will lead to airway restenosis and will require further surgical intervention. In malignant central airway obstructions, patients encounter further morbidity with concomitant intravenous delivery of chemotherapeutics which result in significant systemic side-effect profile. The thesis addresses current shortcomings of improper stent fitting, prevention of granulation tissue formation and local therapy of respiratory cancer relapse, with the development of a controlled drug-eluting stent containing an anti-proliferative drug, paclitaxel. The thesis first evaluates the current state-of-the-art technologies used in the development of respiratory stents to identify knowledge gap withing the field (chapter 1). Subsequently, it evaluates the feasibility of incorporating paclitaxel drug particles into a silicone elastomer that will be used for airway stents and the corresponding drug release profiles from silicone elastomer (chapter 2). Then, alterations on various physicochemical properties of the drug particles and silicone formulations were made to modulate the release kinetics of paclitaxel from the silicone (chapter 3). The efficacy of released paclitaxel was investigated in its ability to control lung cancer (chapter 2) and granulation tissue growth (chapter 5). Finally, the thesis discusses two methods used to develop a more fitting airway stent: 1) using a novel 3D-printing platform in the creation of a surgical guide (chapter 4) and 2) development of a silicone casting platform that is personalisable to individual patient airway geometry (chapter 5)

Dynamic Analysis of X-ray Angiography for Image-Guided Coronary Interventions

Percutaneous coronary intervention (PCI) is a minimally-invasive procedure for treating patients with coronary artery disease. PCI is typically performed with image guidance using X-ray angiograms (XA) in which coronary arter

Book of Abstracts 15th International Symposium on Computer Methods in Biomechanics and Biomedical Engineering and 3rd Conference on Imaging and Visualization

In this edition, the two events will run together as a single conference, highlighting the strong connection with the Taylor & Francis journals: Computer Methods in Biomechanics and Biomedical Engineering (John Middleton and Christopher Jacobs, Eds.) and Computer Methods in Biomechanics and Biomedical Engineering: Imaging and Visualization (JoãoManuel R.S. Tavares, Ed.). The conference has become a major international meeting on computational biomechanics, imaging andvisualization. In this edition, the main program includes 212 presentations. In addition, sixteen renowned researchers will give plenary keynotes, addressing current challenges in computational biomechanics and biomedical imaging. In Lisbon, for the first time, a session dedicated to award the winner of the Best Paper in CMBBE Journal will take place. We believe that CMBBE2018 will have a strong impact on the development of computational biomechanics and biomedical imaging and visualization, identifying emerging areas of research and promoting the collaboration and networking between participants. This impact is evidenced through the well-known research groups, commercial companies and scientific organizations, who continue to support and sponsor the CMBBE meeting series. In fact, the conference is enriched with five workshops on specific scientific topics and commercial software.info:eu-repo/semantics/draf

Modeling Active Anisotropic Materials Undergoing Finite Deformations

Biological and synthetic active materials have attracted a large amount of research attention over the last decade. This thesis is focuses on the development of constitutive models and computational frameworks for describing the behavior of active anisotropic materials. Active anisotropic materials are defined as consisting of an isotropic matrix embedded with fibers or oriented particles that are active. In this dissertation, new constitutive formulations for active anisotropic materials undergoing finite deformations are proposed and analyzed within a generalized continuum mechanics framework. The constitutive equations have been developed for two material classes: i) natural biological muscle tissue and ii) synthetic electroactive polymers. The proposed constitutive models are successfully implemented into a finite element environment to study a range of initial boundary value problems. In the first material class, a structure-based continuum model is proposed to capture the viscoelastic behavior due to smooth muscle tissue contractility. We employed a thick-walled model for healthy and diseased arteries to investigate the effect of active viscoelasticity on the mechanical response of the artery wall. The work focuses on the artery being overstretched on long time scales (around 1 minute), for example, during surgical events such as balloon angioplasty and stent implantation. Model results show an over fourfold increase in circumferential stresses and twofold increase in radial stresses when active viscoelasticity is considered. This suggests that active viscoelasticity has a non-negligible effect on the artery wall stresses when longer timescales are considered. In the second material class, a novel dielectric elastomer composite consisting of an isotropic matrix and embedded contractile fibers is proposed. Two activation modes are realized: through thickness actuation of the matrix and fiber actuation in the plane. A constitutive model is proposed to model the active anisotropic material behavior. A new user subroutine was developed for the proposed constitutive model and implemented into the commercial finite element software ABAQUS. A series of computational simulations to highlight novel deformation modes of the proposed dielectric elastomer composite are presented. The proposed composite significantly extends the actuation performance space for dielectric elastomers. Several new spatial architectures are proposed and the simulations demonstrate coordinated surface morphing through spatial activation and as a function of fiber orientation. Finally, we calculate the actuation response for complex 3D geometries, which opens the design space even further. The developed computational framework is demonstrated to be a very convenient and efficient numerical tool to study complex materials.PHDAerospace EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/138722/1/yalili_1.pd