BACKGROUND: The aorta is the main vessel of the systemic circulation, and its compliant behavior is thought to have an important role in the progression of cardiovascular diseases. Understanding the distensibility features of the aorta can lead to better comprehension of the hemodynamics and its changes in normal and pathologic conditions. In vitro experimentations represents a potential method to elucidate hemodynamic dysfunctions or to test endovascular treatments methods. OBJECTIVE: The main goal of this work was to fabricate compliant human aortas by means of CAD modelling, 3D printing and injection molding techniques. The resulting aortic phantom had to be anatomically correct, compliant and transparent, thus suitable for optical flow investigations such as Particle Image Velocimetry (PIV). The second main goal of the thesis was to elaborate a Simulink lumped parameter model mimicking a pulse replicator for heart valve testing which included the developed aorta model. MATERIALS AND METHODS: Diameters, lengths, angulations and thickness represented the main design parameters of the aortic model and were found in literature. The aortic model was designed using the CAD design software SolidWorks. A selection among the countless materials made available by additive manufacturing has been done. The smoothing susceptibility of the material was chose as the main discriminating factor due to the transparency requirement. To mimic the aortic compliant behavior, two different silicones were employed for the manufacturing of the phantoms. RESULTS: Static distensibility tests on two aortic phantoms realized with Elastosil 601 and Sylgard 184 silicones were performed. The static tests proved that the silicone phantoms reproduce physiological distensibility of subjects in a range of age between 50 and 70 years old. Moreover, the aortic phantoms casted using Sylgard 184 showed an acceptable degree of transparency for quantitative flow investigation techniques. The Simulink model showed to be in good adherence to its physical counterpart, revealing similar aortic and ventricular pressures.
STATO DELL'ARTE: L’aorta è la principale arteria della circolazione sistemica, ed il suo comportamento compliante si ritiene abbia un ruolo importante nella patogenesi di numerose malattie cardiovascolari. Lo studio delle caratteristiche di distensibilità dell’aorta porterebbe ad una migliore comprensione dell'emodinamica in condizioni fisiologiche e dei suoi cambiamenti in condizioni patologiche. Le sperimentazioni in vitro, oltre a permettere di testare tecniche di trattamento endovascolare, rappresentano un metodo potenzialmente ideale per studiare l’emodinamica di un distretto vascolare. OBIETTIVI: L'obiettivo principale di questo lavoro ha riguardato la produzione di modelli compianti di aorta umana attraverso l’utilizzo combinato della modellazione CAD, della stampa 3D e di tecniche di injection moulding. Il modello aortico risultante doveva essere anatomicamente conforme, compliante e trasparente, dunque adatto a metodi di misura ottici del moto di un fluido come la Particle Image Velocimetry (PIV). Il secondo obiettivo della tesi è stato l’elaborazione di un modello a parametri concentrati utilizzando Simulink, rappresentativo di un replicatore di impulsi per il test di valvole cardiache che includeva il modello aortico sviluppato. MATERIALI E METODI: I principali parametri di progetti sono stati diametri, lunghezze, angoli e spessori e sono stati ricercati in letteratura. La progettazione del modello aortico è stata condotta utilizzando il software di modellazione CAD SolidWorks. È seguita poi una selezione tra i numerosi materiali attualmente resi disponibili dalla tecnologia di stampa 3D. Il principale fattore discriminante che ne ha permesso l’individuazione è stato la predisposizione del materiale a trattamenti superficiali affinché il requisito della trasparenza fosse rispettato. Due diversi siliconi sono stati impiegati per la fabbricazione dei modelli aortici affinché il requisito della compliance venisse soddisfatto. RISULTATI: Test di distensibilità statica sono stati condotti su due modelli aortici realizzati utilizzando due siliconi, Elastosil 601 and Sylgard 184. I risultati dei test hanno dimostrato come i modelli in silicone fossero in grado di riprodurre la distensibilità fisiologica di soggetti di età compresa tra 50 e 70 anni. Inoltre, il modello aortico realizzato in Sylgard 184 ha mostrato un grado accettabile di trasparenza, indispensabile per indagini quantitative sul flusso. Le simulazioni risultanti dal modello Simulink ne hanno dimostrato la comparabilità con la sua controparte fisica, rivelando simili pressioni aortiche e ventricolari.
Design and manufacturing of a compliant aortic model by means of CAD modelling and 3D printing
Armagno, Andrea
2019/2020
Abstract
BACKGROUND: The aorta is the main vessel of the systemic circulation, and its compliant behavior is thought to have an important role in the progression of cardiovascular diseases. Understanding the distensibility features of the aorta can lead to better comprehension of the hemodynamics and its changes in normal and pathologic conditions. In vitro experimentations represents a potential method to elucidate hemodynamic dysfunctions or to test endovascular treatments methods. OBJECTIVE: The main goal of this work was to fabricate compliant human aortas by means of CAD modelling, 3D printing and injection molding techniques. The resulting aortic phantom had to be anatomically correct, compliant and transparent, thus suitable for optical flow investigations such as Particle Image Velocimetry (PIV). The second main goal of the thesis was to elaborate a Simulink lumped parameter model mimicking a pulse replicator for heart valve testing which included the developed aorta model. MATERIALS AND METHODS: Diameters, lengths, angulations and thickness represented the main design parameters of the aortic model and were found in literature. The aortic model was designed using the CAD design software SolidWorks. A selection among the countless materials made available by additive manufacturing has been done. The smoothing susceptibility of the material was chose as the main discriminating factor due to the transparency requirement. To mimic the aortic compliant behavior, two different silicones were employed for the manufacturing of the phantoms. RESULTS: Static distensibility tests on two aortic phantoms realized with Elastosil 601 and Sylgard 184 silicones were performed. The static tests proved that the silicone phantoms reproduce physiological distensibility of subjects in a range of age between 50 and 70 years old. Moreover, the aortic phantoms casted using Sylgard 184 showed an acceptable degree of transparency for quantitative flow investigation techniques. The Simulink model showed to be in good adherence to its physical counterpart, revealing similar aortic and ventricular pressures.File | Dimensione | Formato | |
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https://hdl.handle.net/10589/164435