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Segrate, Italy

Stevanella M.,Polytechnic of Milan | Maffessanti F.,Polytechnic of Milan | Conti C.A.,Polytechnic of Milan | Votta E.,Polytechnic of Milan | And 5 more authors.
Cardiovascular Engineering and Technology | Year: 2011

We aim at testing the possibility to build patient-specific structural finite element models (FEMs) of the mitral valve (MV) from cardiac magnetic resonance (CMR) imaging and to use them to predict the outcome of mitral annuloplasty procedures. MV FEMs were built for one healthy subject and for one patient with ischemic mitral regurgitation. On both subjects, CMR imaging of 18 long-axis planes was performed with a temporal resolution of 55 time-frames per cardiac cycle. Three-dimensional MV annulus geometry, leaflets surface and PM position were manually obtained using custom software. Hyperelastic anisotropic mechanical properties were assigned to MV tissues. A physiological pressure load was applied to the leaflets to simulate valve closure until peak systole. For the pathological model only, a further simulation was run, simulating undersized rigid annuloplasty before valve closure. Closure dynamics, leaflets stresses and tensions in the subvalvular apparatus in the healthy MV were consistent with previous computational and experimental data. The regurgitant valve model captured with good approximation the real size and position of regurgitant areas at peak systole, and highlighted abnormal tensions in the annular region and sub-valvular apparatus. The simulation of undersized rigid annuloplasty showed the restoration of MV continence and normal tensions in the subvalvular apparatus and at the annulus. Our method seems suitable for implementing detailed patient-specific MV FEMs to simulate different scenarios of clinical interest. Further work is mandatory to test the method more deeply, to reduce its computational time and to expand the range of modeled surgical procedures. © 2010 Biomedical Engineering Society. Source

Gallo D.,Polytechnic University of Turin | Ponzini R.,CILEA | Isu G.,Polytechnic University of Turin | Pennella F.,Polytechnic University of Turin | And 5 more authors.
ECCOMAS 2012 - European Congress on Computational Methods in Applied Sciences and Engineering, e-Book Full Papers | Year: 2012

We analyse the impact that assumptions regarding the velocity profile at the inlet section of the ascending aorta (measured vs. idealised inlet boundary conditions) have in terms of wall shear stress (WSS) distribution at the luminal surface and helical flow structures. To do it, the results within a computational model with incorporated instantaneous PC MRI measured 3D velocity profiles as inlet are compared with results obtained prescribing the same measured flow rate as inlet BC in terms of idealized flat velocity profile. Technically, steady-state flow simulations were carried out at different phases of the cardiac cycle. Our results show that: (1) when an idealized velocity profile is prescribed at the inlet section, large areas of the luminal surface are affected by differences in instantaneous WSS values of more than 400% with respect to the values obtained by imposing the measured subject specific 3D velocity profile; (2) the assumption on the shape of the inlet velocity profile largely affects the instantaneous topology of the bulk flow in the proximal aorta. Even if the present study must be considered as preliminary, we conclude that the plausibility of the assumption of idealized velocity profiles as inlet BCs in personalized model of the aortic hemodynamics could not hold true. Source

Biancolini M.E.,University of Rome Tor Vergata | Ponzini R.,CILEA | Antiga L.,Orobix | Morbiducci U.,Polytechnic University of Turin
Computational Modelling of Objects Represented in Images: Fundamentals, Methods and Applications III - Proceedings of the International Symposium, CompIMAGE 2012 | Year: 2012

Engineering applications involving biological fluids have highly transversal requirements in terms of domain definition from clinical images, complex flow conditions, rheological properties of fluids, structure motion and deformation, visualization and post-processing of the results. For these reasons, a properly tailored computer-aided-engineering workflow represents an elective environment where to perform realistic hemodynamics studies. Nowadays a large part of the technological requirements needed to tackle these problems in a computational environment are already available in open source and/or commercial codes. Nevertheless, success still strongly depends on technical knowledge and best practice. In otherwords, the design of theworkflow must be translated into a stable and usable framework. Here we present a new workflow based on three fully validated software used to effectively fulfill the requirements related to hemodynamics: theVascular Modeling Toolkit (VMTK) for the pre-processing step (i.e., from clinical images-to-anatomic models); the mesh morphing tool RBF Morph to impose changes to the vascular anatomy;Ansys Fluent as solver of the governing equations of fluid motion.As a first test casewe focused our attention on the study of a realistic model of carotid bifurcation, where geometrical factors such as bifurcation angle and the bulb flare are deformed starting from image-based models. In perspective the herein proposed workflow could be a powerful tool supporting image-based surgical planning optimization in several arterial districts. © 2012 Taylor & Francis Group. Source

Ponzini R.,CILEA | Biancolini M.E.,University of Rome Tor Vergata | Rizzo G.,CNR Institute of Molecular Bioimaging and Physiology | Morbiducci U.,Polytechnic University of Turin
Computational Modelling of Objects Represented in Images: Fundamentals, Methods and Applications III - Proceedings of the International Symposium, CompIMAGE 2012 | Year: 2012

Non-invasive quantitative map of blood flowing in the cardiovascular system is now feasible thanks to imaging techniques (PC MRI). The potentiality of PC MRI data are only poorly exploited due to the limited spatial and temporal accuracy (pixel size, slice-thickness, number of time frames per cardiac cycle). As a consequence, advanced in vivo quantitative hemodynamics cannot be fully exploited as well. A possible approach to overcome some of the limitations consists in the application of interpolation strategies. In this work we test for the first time the reliability of Radial Basis Function theory (RBF) to interpolate blood flow fields in the human aortic arch. Thanks to a previously validated synthetic PC MRI data generator, a quantitative analysis of the percentage error distribution with respect to a gold standard flow field has been performed. The obtained results clearly show that the new method is well suited for this kind of application limiting the error values below 5% in almost every zone of the bulk flow. © 2012 Taylor & Francis Group. Source

Arnoldi A.,Polytechnic of Milan | Invernizzi A.,CILEA | Ponzini R.,CILEA | Votta E.,Polytechnic of Milan | And 2 more authors.
Innovations and Advances in Computer Sciences and Engineering | Year: 2010

A new approach in the biomechanical analysis of the mitral valve (MV) focusing on patient-specific modelling has recently been pursued. The aim is to provide a useful tool to be used in clinic for hypotheses testing in pre-operative surgical planning and post-operative follow-up prediction. In particular, the integration of finite element models (FEMs) with 4D echocardiographic advanced images processing seems to be the key turn in patient-specific modelling. The development of this approach is quite slow and hard, due to three main limitations: i) the time needed for FEM preparation; ii) the high computational costs of FEM calculation; iii) the long learning curve needed to complete the analysis without a unified integrated tool which is not currently available. In this context, the purpose of this work is to present a novel Python-based graphic user interface (GUI) software working in a high performance computing (HPC) environment, implemented to overcome the above mentioned limitations. The Mitral Valve Models Reconstructor (MVMR) integrates all the steps needed to simulate the dynamic closure of a MV through a structural model based on human in vivo experimental data. MVMR enables the FEM reconstruction of the MV by means of efficient scientific routines, which ensure a very small time consuming and make the model easily maintainable. Results on a single case study reveal that both FEM building and structural computation are notably reduced with this new approach. The time needed for the FEM implementation is reduced by 1900% with respect to the previous manual procedure, while the time originally needed for the numerical simulation on a single CPU is decreased by 980% through parallel computing using 32 CPUs. Moreover the user-friendly graphic interface provides a great usability also for non-technical personnel like clinicians and bio-researchers, thus removing the need for a long learning curve. © Springer Science+Business Media B.V. 2010. Source

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