Structural analysis of the interaction between different types of stent and the tracheal tissue.

Questo progetto mira ad analizzare le deformazioni e le sollecitazioni prodotte nel tessuto tracheale quando viene inserito uno stent, per determinare il danno prodotto. Gli stent sono dispositivi a molla. Il loro inserimento mira ad aprire l'interno della trachea ristretta per facilitare il passaggio dell'aria attraverso la trachea. In particolare, i modelli di stent analizzati in questo progetto sono modelli in silicone attualmente in fase di sperimentazione presso l'Università di Saragozza. Questi modelli vengono confrontati con uno stent commerciale prodotto da Novatech, il Dumon. Allo stesso modo, per risolvere i problemi di biocompatibilità e per ottenere una rigidità elastica più simile a quella dei tessuti biologici, sono stati testati altri materiali, come il Polyvinyl alcohol (PVA) e il Polydimethylsiloxane (PDMS). In questo studio, confrontiamo tre modelli di stent simili tra loro ma con alcune modifiche nella geometria della superficie esterna del prodotto. Infatti, la parte esterna degli stent è stata progettata con una struttura esterna di rinforzo, simile a quella dei tipici stent metallici a X. L'attenzione si è concentrata sul comportamento strutturale degli stent, valutato attraverso un software con metodo agli elementi finiti. In tutti i calcoli eseguiti durante il progetto, è stata simulata una morfologia semplificata della trachea di coniglio, cioè una sezione della trachea è stata simulata come un cilindro in cui sono stati differenziati due materiali, cartilagine e muscolo. Dalla letteratura esistente è stato tratto un modello già presente per simulare il ciclo respiratorio del coniglio. In conclusione, il modello computazionale è in grado di progettare, analizzare e caratterizzare il dispositivo con i vincoli e i requisiti del progetto.This project aims to analyse the deformations and stresses produced in the tracheal tissue when a stent is inserted, to determine the damage produced. Stents are springs as devices. Their placement aims to open the inside of the narrowed trachea to facilitate the passage of air through the trachea. In particular, the stent models analysed in this project are silicon stent models currently being tested at the University of Zaragoza. These models are also compared with a commercial stent made by Novatech, the Dumon. Similarly, to solve biocompatibility problems and for a more similar elastic rigidity with biological tissues, other materials were tested, such as Polyvinyl alcohol (PVA) and Polydimethylsiloxane (PDMS). In this study, we compare three stent models that are similar to each other but with certain modifications in the geometry of the external surface of the product. In fact, the outside of the stents was designed with an upward reinforcing structure that is similar to the typical X-pattern metallic stents. Attention was focused on the stents' structural behaviour, evaluated through a Finite Element Method software. In all the calculations performed during the project, a simplified morphology of a rabbit trachea was simulated, i.e. a section of the trachea was simulated as a cylinder in which two materials, cartilage and muscle, were differentiated. An already present model to simulate the respiratory cycle of a rabbit was drawn from the existing literature. In conclusion, the computational model is capable of designing, analysing and characterizing the device with the constraints and the requirements of the project

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)

Variational methods for modeling and simulation of tool-tissue interaction

Ph.DDOCTOR OF PHILOSOPH

Radiological Society of North America (RSNA) 3D printing Special Interest Group (SIG): Guidelines for medical 3D printing and appropriateness for clinical scenarios

Este número da revista Cadernos de Estudos Sociais estava em organização quando fomos colhidos pela morte do sociólogo Ernesto Laclau. Seu falecimento em 13 de abril de 2014 surpreendeu a todos, e particularmente ao editor Joanildo Burity, que foi seu orientando de doutorado na University of Essex, Inglaterra, e que recentemente o trouxe à Fundação Joaquim Nabuco para uma palestra, permitindo que muitos pudessem dialogar com um dos grandes intelectuais latinoamericanos contemporâneos. Assim, buscamos fazer uma homenagem ao sociólogo argentino publicando uma entrevista inédita concedida durante a sua passagem pelo Recife, em 2013, encerrando essa revista com uma sessão especial sobre a sua trajetória

SIMULATION-BASED DESIGN AND MATERIAL MODELING FOR ENT IMPLANTS

Ph.DDOCTOR OF PHILOSOPH