A finite strain nonlinear human mitral valve model with fluid structure interaction

A simulated human mitral valve under a physiological pressure loading is developed using a hybrid finite element immersed boundary method, which incorporates experimentally based constitutive laws in a three-dimensional fluid-structure interaction framework. A transversely isotropic material constitutive model is used for characterizing the mechanical behaviour of the mitral valve tissue based on recent mechanical tests of healthy human mitral leaflets. Our results show good agreement, in terms of the flow rate and the closing and opening configurations, with the measurements from the magnetic resonance images. The stresses in the anterior leaflet are found to be higher than those in the posterior leaflet, and concentrated around the annulus trigons and free edges of the valve leaflets. Those areas are located where the leaflet has the highest curvature. Effects of the chordae tendineae in the material model are studied and the results show that these chordae play an important role in providing a secondary orifice for the flow when valve opens. Although there are some discrepancies to be overcome in future works, our simulations show that the developed computational model is promising in mimicking the in vivo mitral valve dynamics and providing important information that are not obtainable by in vivo measurements. This article is protected by copyright. All rights reserved

Is it possible to assess the best mitral valve repair in the individual patient? Preliminary results of a finite element study from magnetic resonance imaging data

ObjectivesFinite element modeling was adopted to quantitatively compare, for the first time and on a patient-specific basis, the biomechanical effects of a broad spectrum of different neochordal implantation techniques for the repair of isolated posterior mitral leaflet prolapse.MethodsCardiac magnetic resonance images were acquired from 4 patients undergoing surgery. A patient-specific 3-dimensional model of the mitral apparatus and the motion of the annulus and papillary muscles were reconstructed. The location and extent of the prolapsing region were confirmed by intraoperative findings, and the mechanical properties of the mitral leaflets, chordae tendineae and expanded polytetrafluoroethylene neochordae were included. Mitral systolic biomechanics was simulated under preoperative conditions and after 5 different neochordal procedures: single neochorda, double neochorda, standard neochordal loop with 3 neochordae of the same length and 2 premeasured loops with 1 common neochordal loop and 3 different branched neochordae arising from it, alternatively one third and two thirds of the entire length.ResultsThe best repair in terms of biomechanics was achieved with a specific neochordal technique in the single patient, according to the location of the prolapsing region. However, all techniques achieved a slight reduction in papillary muscle forces and tension relief in intact native chordae proximal to the prolapsing region. Multiple neochordae implantation improved the repositioning of the prolapsing region below the annular plane and better redistributed mechanical stresses on the leaflet.ConclusionsAlthough applied on a small cohort of patients, systematic biomechanical differences were noticed between neochordal techniques, potentially affecting their short- to long-term clinical outcomes. This study opens the way to patient-specific optimization of neochordal techniques

Consolidación y fragmentación de la investigación de la comunicación en México, 1987-1997

Este artículo expone de una manera breve y general las conclusiones del trabajo de investigación sobre los procesos de estructuración del campo de la investigación académica de la comunicación en México de 1987 a 1997. El acercamiento empírico exploratorio de este trabajo supone el acopio y la sistematización de datos sobre la producción mexicana de conocimiento sobre la comunicación y sus condiciones contextuales; sobre sus productores, tanto individuales como institucionales; y sobre sus productos objetivos, especialmente las publicaciones académicas. A partir de los resultados del análisis de toda esta información, se construyó un modelo heurístico de las determinaciones socioculturales de la estructuración del campo desde la década de 1960 hasta la de 1990, que permite formular la "doble disyuntiva" que se enfrentó en los años noventa para alcanzar la legitimación académica y social

Mitral Valve Patient-Specific Finite Element Modeling from Cardiac MRI: Application to an Annuloplasty Procedure

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Development of a patient-specific atrial phantom model for planning and training of inter-atrial interventions

Article is accepted for publicationBackgroundSeveral authors have presented cardiac phantoms to mimic the particularities of the heart, making it suitable for medical training and surgical planning. Although the initial models were mainly focused on the ventricles, personalized phantoms of the atria were recently presented. However, such models are typically rigid, the atrial wall is not realistic and they are not compatible with ultrasound (US), being sub-optimal for planning/training of several interventions. MethodsIn this work, we propose a strategy to construct a patient-specific atrial model. Specifically, the target anatomy is generated using a computed tomography (CT) dataset and then constructed using a mold-cast approach. An accurate representation of the inter-atrial wall (IAS) was ensured during the model generation, allowing its application for IAS interventions. Two phantoms were constructed using different flexible materials (silicone and polyvinyl alcohol cryogel, PVA-C), which were then compared to assess their appropriateness for US acquisition and for the generation of complex anatomies. ResultsTwo experiments were set up to validate the proposed methodology. First, the accuracy of the manufacturing approach was assessed through the comparison between a post-production CT and the virtual references. The results proved that the silicone-based model was more accurate than the PVA-C-based one, with an error of 1.680.79, 1.36 +/- 0.94, 1.45 +/- 0.77mm for the left (LA) and right atria (RA) and IAS, respectively. Second, an US acquisition of each model was performed and the obtained images quantitatively and qualitatively assessed. Both models showed a similar performance in terms of visual evaluation, with an easy detection of the LA, RA, and the IAS. Furthermore, a moderate accuracy was obtained between the atrial surfaces extracted from the US and the ideal reference, and again a superior performance of the silicone-based model against the PVA-C phantom was observed. ConclusionsThe proposed strategy proved to be accurate and feasible for the correct generation of complex personalized atrial models.The authors acknowledge "Fundacao para a Ciencia e a Tecnologia" (FCT), in Portugal, and the European Social Found, European Union, for funding support through the "Programa Operacional Capital Humano" (POCH) in the scope of the PhD grants SFRH/BD/95438/2013 (P. Morais) and SFRH/BD/93443/2013 (S. Queiros).Authors gratefully acknowledge the funding of Projects NORTE-01-0145-FEDER-000013 and NORTE-01-0145-FEDER-000022, cofinanced by "Programa Operacional Regional do Norte" (NORTE2020), through "Fundo Europeu de Desenvolvimento Regional" (FEDER).info:eu-repo/semantics/publishedVersio

Analisi e sviluppo di interventi finalizzati al risparmio energetico e alla minimizzazione dell'impatto ambientale in un impianto di distillazione per la produzione di alcolici

Il lavoro di tesi che segue è stato svolto con l’intento di fornire un esempio di sostenibilità economica ed ambientale per una categoria di interventi volti al miglioramento dell’efficienza energetica nel settore industriale.Per conseguire questi obiettivi si è usufruito dei servizi e della disponibilità di una nota Società di Servizi Energetici:Studio Bartucci S.r.l..Di concerto, si è ritenuto utile sviluppare i concetti citati all’interno di una realtà impiantistica consolidata

Digital Against the Digital

The goal of this digital capstone is to provide the viewer with an exploratory experience designed to untangle some the ramifications of owning and using a social media account. Through the help of a journal that assumes the form of a timeline, this digital capstone illustrates how some of the technologies that power fashionable and successful ways of capturing and sharing personal moments online have hidden roots in environmental issues, communities’ exploitation, political and regulatory decisions, data surveillance practices, and psychological and emotional conditions, especially in adolescents