83 results on '"Montevecchi, Fm"'
Search Results
2. An electrical stimulation-based bioreactor as a platform for in vitro stem cell conditioning analysis
- Author
-
CONSOLO, FILIPPO, Pavesi A, Pietronave S, Zamperone A, Prat M, Montevecchi FM, Redaelli A, Soncini M, Fiore GB, Consolo, Filippo, Pavesi, A, Pietronave, S, Zamperone, A, Prat, M, Montevecchi, Fm, Redaelli, A, Soncini, M, and Fiore, Gb
- Abstract
In this work, we present the design of an electrical stimulation-based bioreactor capable of delivering different and highly controlled electrical stimuli to the culture environment. The device represents an in vitro platform allowing examining selectively the effects of different stimulation patterns on stem cells behaviour. In the design stage, we used a computational approach, aimed at establishing operating conditions delivering a desired uniform electric field distribution within the cell- seeded surface of the culture chamber. The device was validated through in vitro tests exploiting the possibility to promote commitment of adipose-derived stem cellsand human cardiac progentiro cells toward the cardiac phenotype.
- Published
- 2012
3. Towards Cardiovascular Tissue Engineering: Macro to Micro Bioreactors
- Author
-
Soncini M, Pavesi A, Rasponi M, Piraino F, Vismara R, Prat M, Pietronave S, Zamperone A, Moretti M, Draghi L., Montevecchi FM, Redaelli A, Fiore GB, CONSOLO, FILIPPO, Soncini, M, Pavesi, A, Rasponi, M, Piraino, F, Vismara, R, Consolo, Filippo, Prat, M, Pietronave, S, Zamperone, A, Moretti, M, Draghi, L., Montevecchi, Fm, Redaelli, A, and Fiore, Gb
- Published
- 2011
4. An electrical stimulation-based bioreactor for cardiomyogenic differentiation of mouse adult stem cells
- Author
-
Pavesi A, Zamperone A, Pietronave S, Prat M, Montevecchi FM, Redaelli A, Fiore GB, Soncini M., CONSOLO, FILIPPO, Pavesi, A, Consolo, Filippo, Zamperone, A, Pietronave, S, Prat, M, Montevecchi, Fm, Redaelli, A, Fiore, Gb, and Soncini, M.
- Published
- 2010
5. A computational model for the optimization of transport phenomena in a rotating hollow fiber bioreactor for artificial liver
- Author
-
CONSOLO, FILIPPO, FIORE GB, TRUSCELLO S, CARONNA M, MORBIDUCCI U, MONTEVECCHI FM, REDAELLI A., Consolo, Filippo, Fiore, Gb, Truscello, S, Caronna, M, Morbiducci, U, Montevecchi, Fm, and Redaelli, A.
- Published
- 2009
6. Using computational fluid dynamics for the computer-aided design of a rotating hollow fiber bioreactor for artificial liver
- Author
-
CONSOLO, FILIPPO, FIORE GB, CARONNA M, MORBIDUCCI U, MONTEVECCHI FM, REDAELLI A., Consolo, Filippo, Fiore, Gb, Caronna, M, Morbiducci, U, Montevecchi, Fm, and Redaelli, A.
- Published
- 2008
7. A CFD computational model for the optimization of transport phenomena in a hollow fiber bioreactor for artificial liver
- Author
-
CONSOLO, FILIPPO, TRUSCELLO S, MONTEVECCHI FM, FIORE GB, REDAELLI A., Consolo, Filippo, Truscello, S, Montevecchi, Fm, Fiore, Gb, and Redaelli, A.
- Published
- 2007
8. An agent-based system model to support cardiac tissue engineering: preliminary results
- Author
-
Gaetano, L, DI BENEDETTO, Giacomo, Morbiducci, Umberto, Montevecchi, Fm, and Hunt, Ca
- Published
- 2010
9. Self organizing map based morphological analysis of oral glucose tolerance test curves in women with gestational diabetes mellitus
- Author
-
Gaetano L, Di Benedetto G, Tura A, Balestra G, Montevecchi FM, Kautzky Willer A, Pacini G, and Morbiducci U
- Published
- 2010
10. Shaping data: a self organizing map approach for data mining of oral glucose tolerance test curves in women with previous gestational diabetes
- Author
-
Gaetano L, Di Benedetto G, Tura A, Balestra G, Montevecchi FM, Kautzky-Willer A, Pacini G, and Morbiducci U
- Published
- 2010
11. Micromixing and microchannel design: Vortex shape and entropy
- Author
-
Mastrangelo, FM, Pennella, F, Consolo, F, Rasponi, M, Redaelli, A, Montevecchi, FM, Morbiducci, U, and 2nd Micro and Nano Flows Conference (MNF2009)
- Subjects
Helicity ,Mixing ,Entropy ,Vortex identification - Abstract
This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications. In very recent years microdevices, due to their potency in replacing large-scale conventional laboratory instrumentation, are becoming a fast and low cost technology for the treatment of several chemical and biological processes. In particular microfluidics has been massively investigated, aiming at improving the performance of chemical reactors. This is because of the fact that reaction is often an interface phenomenon where the greater the surface to volume ratio, the higher the reaction speed, and microscale mixing increases the interfacial area (in terms of mixing-induced-by-vortices generation). However, microfluidic systems suffer from the limitation that they are characterized mostly by very low Reynolds numbers, with the consequence that (i) they cannot take advantage from the turbulence mixing support, and (ii) viscosity hampers proper vortex detection. Therefore, the proper design of micro-channels (MCs) becomes essential. In this framework, several geometries have been proposed to induce mixing vortices in MCs. However a quantitative comparison between proposed geometries in terms of their passive mixing potency can be done only after proper definition of vortex formation (topology, size) and mixing performance. The objective of this study is to test the ability of different fluid dynamic metrics in vortex detection and mixing effectiveness in micromixers. This is done numerically solving different conditions for the flow in a classic passive mixer, a ring shaped MC. We speculate that MCs design could take advantage from fluidic metrics able to rank properly flow related mixing.
- Published
- 2009
12. IN SILICO BIOREACTOR FOR SIMULATING TISSUE ENGINEERING USING A MULTI AGENT MODEL. PRELIMINARY RESULTS
- Author
-
Gaetano, Laura, Antunes, L, DI BENEDETTO, Giacomo, Balestra, Gabriella, Montevecchi, Fm, and Morbiducci, Umberto
- Published
- 2009
13. Propagation and Cardiac Differentiation of Encapsulated Human Embryonic Stem Cells in a Novel Perfused Bioreactor Capable of Ultrasonic Mechanical Stimulation
- Author
-
Bariani, Christian, Montevecchi, Fm, Mantero, S, Ali, Nn, Harding, Se, and Mantalaris, A.
- Published
- 2009
14. Multi agent system for modelling cellular adhesion and migration: a preliminary study
- Author
-
Gaetano, Laura, Massai, DIANA NADA CATERINA, Morbiducci, Umberto, and Montevecchi, Fm
- Published
- 2008
15. Cytocompatibility and morpho-functional characterization of collagen foam for cardiac tissue engineering
- Author
-
Bariani, Christian, Sadr, N, Riboldi, Sa, Arrigoni, C, Remuzzi, A, Montevecchi, Fm, and Mantero, S.
- Published
- 2008
16. Il Tessuto Ematico
- Author
-
Fiore, Gb, Morbiducci, Umberto, Redaelli, A., and Montevecchi, Fm
- Published
- 2007
17. Cell interactions and mechanical properties of 3D porous scaffolds for Tissue Engineering
- Author
-
Bariani, Christian, Sadr, N, Riboldi, Sa, Montevecchi, Fm, and Mantero, S.
- Published
- 2007
18. Does the Ventrica magnetic vascular positioner (MVP(R)) for coronary artery bypass grafting significantly alter local fluid dynamics? A numeric study
- Author
-
Morbiducci, Umberto, Lemma, Massimo, Ponzini, Raffaele, Boi, A, Bondavalli, L, Antona, C, Montevecchi, Fm, and Redaelli, ALBERTO CESARE LUIGI
- Published
- 2007
19. Multiscale modelling in biomechanical applications
- Author
-
Redaelli, A, Soncini, M, Vesentini, S, Votta, E, Deriu, MARCO AGOSTINO, Gautieri, A, Fiore, Gb, Montevecchi, Fm, Enemark, S, Aprodu, I, and Ionita, M.
- Published
- 2007
20. A COMPUTATIONAL TOOL KIT FOR THE CLASSIFICATION OF 2D-ELECTROPHORESIS MAPS BY COMBINATION OF UNSUPERVISED MACHINE LEARNING TECHNIQUES
- Author
-
Cannistraci, CARLO VITTORIO, Malgaroli, M, Montevecchi, Fm, and Alessio, M.
- Published
- 2007
21. Molecular assessment of the elastic properties of collagen-like homotrimer sequences
- Author
-
Vesentini, Simone, Fitie, Cf, Montevecchi, Fm, and Redaelli, ALBERTO CESARE LUIGI
- Published
- 2005
22. A numerical method for the study of red blood cell motion in small vessels
- Author
-
Dubini, GABRIELE ANGELO, Pietrabissa, Riccardo, and Montevecchi, Fm
- Published
- 1994
23. A self-organizing map based morphological analysis of oral glucose tolerance test curves in women with gestational diabetes mellitus.
- Author
-
Gaetano L, Di Benedetto G, Tura A, Balestra G, Montevecchi FM, Kautzky-Willer A, Pacini G, Morbiducci U, Safran C, Reti S, and Marin H
- Published
- 2010
24. Mechanistic insight into the physiological relevance of helical blood flow in the human aorta: an in vivo study
- Author
-
Marcello Cadioli, Alberto Redaelli, Umberto Morbiducci, Giovanna Rizzo, Franco Maria Montevecchi, Antonio Esposito, Raffaele Ponzini, Morbiducci, U, Ponzini, R, Rizzo, G, Cadioli, M, Esposito, Antonio, Montevecchi, Fm, and Redaelli, A.
- Subjects
Aortic arch ,Adult ,Time Factors ,Hemodynamics ,Contrast Media ,4D phase-contrast MRI ,Spiral flow ,Fluid mechanics ,Young Adult ,Nuclear magnetic resonance ,medicine.artery ,medicine ,Thoracic aorta ,Humans ,Aorta ,Physics ,Mechanical Engineering ,Blood flow ,Vorticity ,Fluid transport ,Magnetic Resonance Imaging ,Biomechanical Phenomena ,Perfusion ,Flow (mathematics) ,Modeling and Simulation ,Blood Circulation ,Algorithms ,Biotechnology ,Biomedical engineering - Abstract
The hemodynamics within the aorta of five healthy humans were investigated to gain insight into the complex helical flow patterns that arise from the existence of asymmetries in the aortic region. The adopted approach is aimed at (1) overcoming the relative paucity of quantitative data regarding helical blood flow dynamics in the human aorta and (2) identifying common characteristics in physiological aortic flow topology, in terms of its helical content. Four-dimensional phase-contrast magnetic resonance imaging (4D PC MRI) was combined with algorithms for the calculation of advanced fluid dynamics in this study. These algorithms allowed us to obtain a 4D representation of intra-aortic flow fields and to quantify the aortic helical flow. For our purposes, helicity was used as a measure of the alignment of the velocity and the vorticity. There were two key findings of our study: (1) intra-individual analysis revealed a statistically significant difference in the helical content at different phases of systole and (2) group analysis suggested that aortic helical blood flow dynamics is an emerging behavior that is common to normal individuals. Our results also suggest that helical flow might be caused by natural optimization of fluid transport processes in the cardiovascular system, aimed at obtaining efficient perfusion. The approach here applied to assess in vivo helical blood flow could be the starting point to elucidate the role played by helicity in the generation and decay of rotating flows in the thoracic aorta.
- Published
- 2009
25. In vivo quantification of helical blood flow in human aorta by time-resolved three-dimensional cine phase contrast magnetic resonance imaging
- Author
-
Francesco De Cobelli, Alessandro Del Maschio, Antonio Esposito, Umberto Morbiducci, Alberto Redaelli, Raffaele Ponzini, Marcello Cadioli, Franco Maria Montevecchi, Giovanna Rizzo, Morbiducci, U, Ponzini, R, Rizzo, G, Cadioli, M, Esposito, Antonio, DE COBELLI, Francesco, DEL MASCHIO, Alessandro, Montevecchi, Fm, and Redaelli, A.
- Subjects
Human aorta ,Physics ,Aorta ,Biomedical Engineering ,Models, Cardiovascular ,Hemodynamics ,Magnetic Resonance Imaging, Cine ,Blood Pressure ,Blood flow ,Phase contrast magnetic resonance imaging ,medicine.anatomical_structure ,Imaging, Three-Dimensional ,In vivo ,Ventricle ,medicine.artery ,Pulsatile Flow ,Image Interpretation, Computer-Assisted ,medicine ,Humans ,Computer Simulation ,Systole ,Blood Flow Velocity ,Biomedical engineering - Abstract
The mechanics of blood flow in arteries plays a key role in the health of individuals. In this framework, the role played by the presence of helical flow in the human aorta is still not clear in its relation to physiology and pathology. We report here a method for quantifying helical flow in vivo employing time-resolved cine phase contrast magnetic resonance imaging to obtain the complete spatio-temporal description of the three-dimensional pulsatile blood flow patterns in aorta. The method is applied to data of one healthy volunteer. Particle traces were calculated from velocity data: to them we applied a Lagrangian-based method for helical flow quantification, the Helical Flow Index, which has been developed and evaluated in silico in order to reveal global organization of blood flow. Our results: (i) put in evidence that the systolic hemodynamics in aorta is characterized by an evolving helical flow (we quantified a 24% difference in terms of the content of helicity in the streaming blood, between mid and early systole); (ii) indicate that in the first part of the systole helicity is ascrivable mainly to the asymmetry of blood flow in the left ventricle, joined with the laterality of the aorta. In conclusion, this study shows that the quantification of helical blood flow in vivo is feasible, and it might allow detection of anomalies in the expected physiological development of helical flow in aorta and accordingly, could be used in a diagnostic/prognostic index for clinical practice The mechanics of blood flow in arteries plays a key role in the health of individuals. In this framework, the role played by the presence of helical flow in the human aorta is still not clear in its relation to physiology and pathology. We report here a method for quantifying helical flow in vivo employing time-resolved cine phase contrast magnetic resonance imaging to obtain the complete spatio-temporal description of the three-dimensional pulsatile blood flow patterns in aorta. The method is applied to data of one healthy volunteer. Particle traces were calculated from velocity data: to them we applied a Lagrangian-based method for helical flow quantification, the Helical Flow Index, which has been developed and evaluated in silico in order to reveal global organization of blood flow. Our results: (i) put in evidence that the systolic hemodynamics in aorta is characterized by an evolving helical flow (we quantified a 24% difference in terms of the content of helicity in the streaming blood, between mid and early systole); (ii) indicate that in the first part of the systole helicity is ascrivable mainly to the asymmetry of blood flow in the left ventricle, joined with the laterality of the aorta. In conclusion, this study shows that the quantification of helical blood flow in vivo is feasible, and it might allow detection of anomalies in the expected physiological development of helical flow in aorta and accordingly, could be used in a diagnostic/prognostic index for clinical practice.
- Published
- 2008
26. The Geoform disease-specific annuloplasty system: a finite element study
- Author
-
Francesco Maisano, Franco Maria Montevecchi, Alberto Redaelli, Steven F. Bolling, Emiliano Votta, Ottavio Alfieri, Votta, E, Maisano, F, Bolling, Sf, Alfieri, Ottavio, Montevecchi, Fm, and Redaelli, A.
- Subjects
Pulmonary and Respiratory Medicine ,Disease specific ,Stress reduction ,Heart Valve Prosthesis Implantation ,medicine.medical_specialty ,business.industry ,medicine.medical_treatment ,Finite Element Analysis ,% area reduction ,Mitral Valve Insufficiency ,Papillary Muscles ,Prosthesis ,System a ,Finite element study ,Surgery ,medicine ,Humans ,Mitral Valve ,Stress, Mechanical ,Cardiology and Cardiovascular Medicine ,business ,Functional mitral regurgitation ,Biomedical engineering - Abstract
Background Functional mitral regurgitation (FMR) is the inability of mitral leaflets to coapt due to a combination of functional and geometrical factors. Valve competence is commonly restored by undersized annuloplasty, reducing the native annulus anteroposterior dimension. In case of severe FMR, this solution may be inadequate. The use of rings specific for the correction of FMR may lead to better results. Methods The performance of the Geoform ring, a recently designed FMR-specific prosthesis, was compared with that of a standard Physio annuloplasty ring. Finite element modeling was used to simulate dilated cordiomyopathy-related FMR and compare, at the systolic peak, the valve's pathologic condition with the postoperative scenario corresponding to both devices. Three degrees of the pathology were simulated by progressively displacing papillary muscles apically, up to 5 mm. Three ring sizes were modeled. Results Regurgitant area, coaptation length, and stresses acting on valve structures were assessed. When the use of the Geoform was modeled, coaptation length was always longer than 7 mm. In the most unfavorable case, the regurgitant area reduction was 74% with respect to baseline, and leaflets stresses were reduced by 20% when undersizing was simulated. When Physio ring implantation was simulated, coaptation length maximum extent was equal to 4.3 mm, the maximum regurgitant area reduction was equal to 60%, and leaflet stress reduction was observed. Conclusions Disease-specific prostheses may allow for restoration of valve competence even for significant degrees of leaflets tethering and avoid the need for aggressive undersizing, thus leading to more durable results.
- Published
- 2007
27. Haemodynamics and mechanics following partial left ventriculectomy: a computer modeling analysis
- Author
-
Ottavio Alfieri, Alberto Redaelli, Monica Soncini, Francesco Maisano, Franco Maria Montevecchi, Redaelli, A, Maisano, F, Soncini, M, Alfieri, Ottavio, and Montevecchi, Fm
- Subjects
Cardiomyopathy, Dilated ,medicine.medical_specialty ,Heart Ventricles ,Biomedical Engineering ,Biophysics ,Hemodynamics ,Blood Pressure ,Sensitivity and Specificity ,Afterload ,Heart Rate ,Internal medicine ,medicine ,Animals ,Humans ,Computer Simulation ,Diagnosis, Computer-Assisted ,Cardiac Surgical Procedures ,Mathematics ,Partial left ventriculectomy ,Ejection fraction ,Ventricular Remodeling ,Models, Cardiovascular ,Reproducibility of Results ,Dilated cardiomyopathy ,Stroke Volume ,Stroke volume ,Mechanics ,medicine.disease ,Dilated ventricles ,medicine.anatomical_structure ,Treatment Outcome ,Ventricle ,Hemorheology ,Cardiology - Abstract
Mechanics following partial left ventriculectomy is still poorly understood. A computational cylindrical model of the left ventricle was developed, based on the myocardial fibre behaviour for the evaluation of the mechanical and haemodynamical effects of the operation. A healthy left ventricle with physiological geometry and function and a dilated hypokinetic heart were investigated. Haemodynamic and mechanical data were obtained at baseline and compared with those obtained at different degrees of volume reduction. Data included: ejection fraction (EF); stroke volume (SV); end-systolic and end-diastolic pressure-volume relationships (ESPVR and EDPVR), and efficiency. EF increases following volume reduction in both simulation but, concurrently, SV shows modest improvement (dilated ventricle) or reduction (healthy ventricle) at progressive degrees of resection. The ESPVR and EDPVR slope increases and shifts leftward with the resection extent, but the increase of the ESPVR slope is more pronounced in dilated ventricle. Efficiency is improved in the dilated heart after resections, while does not improve when the healthy-heart volume is reduced. The simulation of partial left ventriculectomy suggests an improvement of systolic performance, counterbalanced by increased diastolic stiffness following inverse remodelling. Efficiency of simulated dilated ventricles is enhanced by volume reduction, suggesting a favourable effect of reduction of the metabolic demand of the failing heart.
- Published
- 2004
28. Flow dynamics of the St Jude Medical Symmetry aortic connector vein graft anastomosis do not contribute to the risk of acute thrombosis
- Author
-
Enrico Cattaneo, G. Ligorio, Franco Maria Montevecchi, Alberto Redaelli, O. Alfieri, Francesco Maisano, Redaelli, A, Maisano, F, Ligorio, G, Cattaneo, E, Montevecchi, Fm, and Alfieri, Ottavio
- Subjects
Pulmonary and Respiratory Medicine ,Aortic valve ,medicine.medical_specialty ,Intimal hyperplasia ,Systole ,Anastomosis ,Veins ,Postoperative Complications ,Risk Factors ,medicine.artery ,Ascending aorta ,medicine ,Humans ,Computer Simulation ,Vein ,Aorta ,Vascular Patency ,Heart Valve Prosthesis Implantation ,business.industry ,Anastomosis, Surgical ,Graft Occlusion, Vascular ,Models, Cardiovascular ,Thrombosis ,Equipment Design ,medicine.disease ,Surgery ,medicine.anatomical_structure ,Aortic Valve ,Acute Disease ,Cardiology and Cardiovascular Medicine ,business ,Blood Flow Velocity ,Artery - Abstract
Background The efficacy of the St Jude Medical Symmetry aortic connector (St Jude Medical, Inc, St Paul, Minn) for coronary artery bypass is currently debated. Potential drawbacks are the biocompatibility of the endoluminal device, the need for graft manipulation during the procedure, and the 90° offset of the vein graft from the ascending aorta, which may induce graft kinking and abnormal fluid dynamics. In this article, a computational approach was designed to investigate the fluid dynamics pattern at the proximal graft. Methods Four models of hand-sewn anastomoses and two models of automated anastomoses were constructed; a finite volume technique was used to simulate realistic graft fluid dynamics, including aortic compliance and proper aortic and graft flow rates. The anastomosis geometry performance was analyzed by calculating time-averaged wall shear stress and the oscillating shear index at the toe and heel regions of the proximal graft. Results Time-averaged wall shear stress was significantly lower in the hand-sewn anastomosis models than in the two models that simulated the use of the aortic connector (0.38 ± 0.07 Pa vs 1.32 ± 0.4 Pa). Higher oscillating shear index values were calculated in the hand-sewn anastomosis models (0.15 ± 0.02 Pa vs 0.06 ± 0.02 Pa). Conclusions Automated anastomosis geometry is associated with less critical fluid dynamics than with conventional hand-sewn anastomosis: the shape of the proximal graft induces more physiological wall shear stresses and less oscillating flow, suggesting a lower risk of atherosclerotic plaque and intimal hyperplasia as compared with conventional anastomosis geometry. Therefore, the reported early thrombosis and late failure of the St Jude Medical aortic connector anastomoses are not related to unfavorable fluid dynamics.
- Full Text
- View/download PDF
29. 3-D computational analysis of the stress distribution on the leaflets after edge-to-edge repair of mitral regurgitation
- Author
-
Votta, E., Maisano, F., Monica Soncini, Redaelli, A., Montevecchi, F. M., Alfieri, O., Votta, E, Maisano, F, Soncini, M, Redaelli, A, Montevecchi, Fm, and Alfieri, Ottavio
- Abstract
Background and aim of the study: Edge-to-edge repair is an effective, recently introduced method to correct mitral insufficiency by suturing the leaflets at the site of regurgitation, though durability of the method has not been proven. To overcome the limitations of the clinical approach, simulations may be used to predict clinical outcome. In this study, the mechanical stress acting on leaflets imposed by the edge-to-edge suture was evaluated as a means of assessing the clinical risk of late fibrosis or tissue degeneration. Methods: A 3-D finite element simulated the stress pattern following edge-to-edge repair. Valve behavior was evaluated both in systole and in diastole. Both 4-mm. and 8-mm edge-to-edge sutures were simulated, as well as annular dilation. Results: Systolic simulations validated the model by comparison with previous models of the mitral valve. Diastolic stresses were negligible in the native mitral valve; after edge-to-edge repair (8-mm. suture), circumferential and longitudinal stress values were 308 kPa and 489 kPa, respectively, and comparable with those observed at systolic peak (449 kPa and 617 kPa, respectively). With a 4-mm suture, longitudinal stresses decreased both close to the suture (-41.5%) and in the annular region (-68%), while circumferential stresses increased (+37%) close to the suture and decreased (-27%) in the annular region. A 20%. dilation of the. annulus was followed by increased stresses in the annular region and close to the suture. Conclusion: Leaflet distortion and altered stress distribution occur on the leaflets after edge-to-edge repair. Diastolic peak stress values were comparable with those calculated in systole. The clinical implication is a doubled exposure of valve components to systolic stresses, as if the heart rate were doubled. The use of a prosthetic annuloplasty ring is favorable in the presence of annular dilation to reduce stresses acting on the leaflets after edge-to-edge repair.
30. Bioreactors as engineering support to treat cardiac muscle and vascular disease.
- Author
-
Massai D, Cerino G, Gallo D, Pennella F, Deriu MA, Rodriguez A, Montevecchi FM, Bignardi C, Audenino A, and Morbiducci U
- Subjects
- Animals, Biomedical Engineering instrumentation, Equipment Design, Equipment Failure Analysis, Heart Diseases pathology, Humans, Myocytes, Cardiac pathology, Vascular Diseases pathology, Bioreactors, Heart Diseases surgery, Myocytes, Cardiac transplantation, Organ Culture Techniques instrumentation, Tissue Engineering instrumentation, Vascular Diseases surgery
- Abstract
Cardiovascular disease is the leading cause of morbidity and mortality in the Western World. The inability of fully differentiated, load-bearing cardiovascular tissues to in vivo regenerate and the limitations of the current treatment therapies greatly motivate the efforts of cardiovascular tissue engineering to become an effective clinical strategy for injured heart and vessels. For the effective production of organized and functional cardiovascular engineered constructs in vitro, a suitable dynamic environment is essential, and can be achieved and maintained within bioreactors. Bioreactors are technological devices that, while monitoring and controlling the culture environment and stimulating the construct, attempt to mimic the physiological milieu. In this study, a review of the current state of the art of bioreactor solutions for cardiovascular tissue engineering is presented, with emphasis on bioreactors and biophysical stimuli adopted for investigating the mechanisms influencing cardiovascular tissue development, and for eventually generating suitable cardiovascular tissue replacements.
- Published
- 2013
- Full Text
- View/download PDF
31. Incorporation of PLGA nanoparticles into porous chitosan-gelatin scaffolds: influence on the physical properties and cell behavior.
- Author
-
Nandagiri VK, Gentile P, Chiono V, Tonda-Turo C, Matsiko A, Ramtoola Z, Montevecchi FM, and Ciardelli G
- Subjects
- Cell Adhesion drug effects, Cell Differentiation drug effects, Cell Line, Cell Survival drug effects, Compressive Strength, Humans, Lactic Acid metabolism, Osteoblasts drug effects, Osteogenesis drug effects, Polyglycolic Acid metabolism, Polylactic Acid-Polyglycolic Acid Copolymer, Porosity, Chitosan chemistry, Gelatin chemistry, Lactic Acid chemistry, Lactic Acid pharmacology, Nanoparticles chemistry, Osteoblasts cytology, Polyglycolic Acid chemistry, Polyglycolic Acid pharmacology, Tissue Scaffolds chemistry
- Abstract
Bone regeneration can be accelerated by localized delivery of appropriate growth factors/biomolecules. Localized delivery can be achieved by a 2-level system: (i) incorporation of biomolecules within biodegradable particulate carriers (nanoparticles), and (ii) inclusion of such particulate carriers (nanoparticles) into suitable porous scaffolds. In this study, freeze-dried porous chitosan-gelatin scaffolds (CH-G: 1:2 ratio by weight) were embedded with various amounts of poly(lactide-co-glycolide) (PLGA) nanoparticles, precisely 16.6%, 33.3% and 66.6% (respect to CH-G weight). Scaffolds loaded with PLGA nanoparticles were subjected to physico-mechanical and biological characterizations including morphological analysis, swelling and dissolution tests, mechanical compression tests and cell viability tests. Results showed that incorporation of PLGA nanoparticles into porous crosslinked CH-G scaffolds: (i) changed the micro-architecture of the scaffolds in terms of mean pore diameter and pore size distribution, (ii) reduced the dissolution degree of the scaffolds, and (iii) increased the compressive modulus. On the other hand, the water uptake behavior of CH-G scaffolds containing PLGA nanoparticles significantly decreased. The incorporation of PLGA nanoparticles did not affect the biocompatibility of CH-G scaffolds., (Copyright © 2011 Elsevier Ltd. All rights reserved.)
- Published
- 2011
- Full Text
- View/download PDF
32. On the importance of blood rheology for bulk flow in hemodynamic models of the carotid bifurcation.
- Author
-
Morbiducci U, Gallo D, Massai D, Ponzini R, Deriu MA, Antiga L, Redaelli A, and Montevecchi FM
- Subjects
- Carotid Artery, External, Carotid Artery, Internal, Computer Simulation, Humans, Carotid Arteries, Hemodynamics, Hemorheology, Models, Biological
- Abstract
Here we present a study on the impact of assumptions on image-based hemodynamic simulations of healthy carotid bifurcations. In particular, we evaluate to which extent assumptions on blood rheology influence bulk flow features, driven by the fact that few studies have provided adequate insights into the influence of assumptions to confidently model the 4D hemodynamics within the bifurcation. The final goal is to complement, integrate and extend with a quantitative characterization of the bulk flow the description currently adopted to classify altered hemodynamics, which is based on wall shear stress (WSS). Hemodynamic simulations of two image-based carotid bifurcation geometries were carried out assuming a reference Newtonian viscosity, two non-Newtonian rheology models and Newtonian viscosities based on characteristic shear rates. WSS-based and Lagrangian-based metrics for helical flow quantification and for vorticity dynamics quantification were calculated. Our findings suggest that the assumption of Newtonian rheology: (1) could be reasonable for bulk flow metrics (differences from non-Newtonian behavior are lower than 10%); (2) influences at different levels the WSS-based indicators, depending on the bifurcation model, even if in our study it is lower than the major source of uncertainty as recognized by the literature (i.e., uncertainty on geometry reconstruction)., (Copyright © 2011 Elsevier Ltd. All rights reserved.)
- Published
- 2011
- Full Text
- View/download PDF
33. Mechanistic insight into the physiological relevance of helical blood flow in the human aorta: an in vivo study.
- Author
-
Morbiducci U, Ponzini R, Rizzo G, Cadioli M, Esposito A, Montevecchi FM, and Redaelli A
- Subjects
- Adult, Algorithms, Biomechanical Phenomena physiology, Contrast Media, Humans, Magnetic Resonance Imaging, Time Factors, Young Adult, Aorta physiology, Blood Circulation physiology, Hemodynamics physiology
- Abstract
The hemodynamics within the aorta of five healthy humans were investigated to gain insight into the complex helical flow patterns that arise from the existence of asymmetries in the aortic region. The adopted approach is aimed at (1) overcoming the relative paucity of quantitative data regarding helical blood flow dynamics in the human aorta and (2) identifying common characteristics in physiological aortic flow topology, in terms of its helical content. Four-dimensional phase-contrast magnetic resonance imaging (4D PC MRI) was combined with algorithms for the calculation of advanced fluid dynamics in this study. These algorithms allowed us to obtain a 4D representation of intra-aortic flow fields and to quantify the aortic helical flow. For our purposes, helicity was used as a measure of the alignment of the velocity and the vorticity. There were two key findings of our study: (1) intra-individual analysis revealed a statistically significant difference in the helical content at different phases of systole and (2) group analysis suggested that aortic helical blood flow dynamics is an emerging behavior that is common to normal individuals. Our results also suggest that helical flow might be caused by natural optimization of fluid transport processes in the cardiovascular system, aimed at obtaining efficient perfusion. The approach here applied to assess in vivo helical blood flow could be the starting point to elucidate the role played by helicity in the generation and decay of rotating flows in the thoracic aorta.
- Published
- 2011
- Full Text
- View/download PDF
34. Biomechanics of actin filaments: a computational multi-level study.
- Author
-
Deriu MA, Bidone TC, Mastrangelo F, Di Benedetto G, Soncini M, Montevecchi FM, and Morbiducci U
- Subjects
- Compressive Strength, Computer Simulation, Elastic Modulus, Protein Conformation, Stress, Mechanical, Tensile Strength, Actin Cytoskeleton chemistry, Actin Cytoskeleton ultrastructure, Actins chemistry, Actins ultrastructure, Models, Chemical, Models, Molecular
- Abstract
The actin microfilament (F-actin) is a structural and functional component of the cell cytoskeleton. Notwithstanding the primary role it plays for the mechanics of the cell, the mechanical behaviour of F-actin is still not totally explored. In particular, the relationship between the mechanics of F-actin and its molecular architecture is not completely understood. In this study, the mechanical properties of F-actin were related to the molecular topology of its building monomers (G-actin) by employing a computational multi-level approach. F-actins with lengths up to 500 nm were modelled and characterized, using a combination of equilibrium molecular dynamics (MD) simulations and normal mode analysis (NMA). MD simulations were performed to analyze the molecular rearrangements of G-actin in physiological conditions; NMA was applied to compute the macroscopic properties of F-actin from its vibrational modes of motion. Results from this multi-level approach showed that bending stiffness, bending modulus and persistence length are independent from the length of F-actin. On the contrary, the orientations and motions of selected groups of residues of G-actin play a primary role in determining the filament flexibility. In conclusion, this study (i) demonstrated that a combined computational approach of MD and NMA allows to investigate the biomechanics of F-actin taking into account the molecular topology of the filament (i.e., the molecular conformations of G-actin) and (ii) that this can be done using only crystallographic G-actin, without the need of introducing experimental parameters nor of reducing the number of residues., (Copyright © 2010 Elsevier Ltd. All rights reserved.)
- Published
- 2011
- Full Text
- View/download PDF
35. Quantitative analysis of bulk flow in image-based hemodynamic models of the carotid bifurcation: the influence of outflow conditions as test case.
- Author
-
Morbiducci U, Gallo D, Ponzini R, Massai D, Antiga L, Montevecchi FM, and Redaelli A
- Subjects
- Biomedical Engineering, Blood Flow Velocity, Carotid Arteries anatomy & histology, Computer Simulation, Hemodynamics, Hemorheology, Humans, Imaging, Three-Dimensional, Carotid Arteries physiology, Models, Cardiovascular
- Abstract
Although flow-driven mechanisms associated with vascular physiopathology also deal with four-dimensional phenomena such as species transport, the majority of the research on the subject focuses primarily on wall shear stress as indicator of disturbed flow. Indeed, the role that bulk flow plays in vascular physiopathology has not been thoroughly investigated, partly because of a lack of descriptors that would be able to reduce the intricacy of arterial hemodynamics. Here, an approach is proposed to investigate, in silico, the bulk flow within the carotid bifurcation. For this purpose, we coupled a three-dimensional model of carotid bifurcation with a lumped model of the downstream vasculature. For the sake of comparison, we also imposed three different fixed flow rate repartitions between the internal and external carotid arteries on the three-dimensional model. The bulk flow was characterized by applying a descriptor of helical motion, the helical flow index (HFI) to the model; the HFI has recently been shown to provide an accurate representation of complex flows. Moreover, a new metric is presented to investigate the vorticity dynamics within the bifurcation. Our results highlight the effectiveness of these metrics in the following contexts: (i) identifying and ranking emerging hemodynamic features and (ii) quantifying the influence of the outflow boundary conditions on the composition of the translational and rotational components of the fluid motion. The metrics applied herein allow for a more comprehensive analysis, which may lead to the development of an instrument to relate the bulk flow to vascular pathophysiological events that involve not only fluid-related forces, but also transport phenomena within blood.
- Published
- 2010
- Full Text
- View/download PDF
36. Anisotropic elastic network modeling of entire microtubules.
- Author
-
Deriu MA, Soncini M, Orsi M, Patel M, Essex JW, Montevecchi FM, and Redaelli A
- Subjects
- Anisotropy, Molecular Dynamics Simulation, Protein Multimerization, Reference Standards, Tubulin chemistry, Elasticity, Microtubules metabolism, Models, Biological
- Abstract
Microtubules are supramolecular structures that make up the cytoskeleton and strongly affect the mechanical properties of the cell. Within the cytoskeleton filaments, the microtubule (MT) exhibits by far the highest bending stiffness. Bending stiffness depends on the mechanical properties and intermolecular interactions of the tubulin dimers (the MT building blocks). Computational molecular modeling has the potential for obtaining quantitative insights into this area. However, to our knowledge, standard molecular modeling techniques, such as molecular dynamics (MD) and normal mode analysis (NMA), are not yet able to simulate large molecular structures like the MTs; in fact, their possibilities are normally limited to much smaller protein complexes. In this work, we developed a multiscale approach by merging the modeling contribution from MD and NMA. In particular, MD simulations were used to refine the molecular conformation and arrangement of the tubulin dimers inside the MT lattice. Subsequently, NMA was used to investigate the vibrational properties of MTs modeled as an elastic network. The coarse-grain model here developed can describe systems of hundreds of interacting tubulin monomers (corresponding to up to 1,000,000 atoms). In particular, we were able to simulate coarse-grain models of entire MTs, with lengths up to 350 nm. A quantitative mechanical investigation was performed; from the bending and stretching modes, we estimated MT macroscopic properties such as bending stiffness, Young modulus, and persistence length, thus allowing a direct comparison with experimental data., (Copyright © 2010 Biophysical Society. Published by Elsevier Inc. All rights reserved.)
- Published
- 2010
- Full Text
- View/download PDF
37. Nonlinear dimension reduction and clustering by Minimum Curvilinearity unfold neuropathic pain and tissue embryological classes.
- Author
-
Cannistraci CV, Ravasi T, Montevecchi FM, Ideker T, and Alessio M
- Subjects
- Artificial Intelligence, Cell Line, Cluster Analysis, Embryo, Mammalian cytology, Humans, Peripheral Nervous System Diseases cerebrospinal fluid, Transcription Factors genetics, Algorithms, Data Interpretation, Statistical, Pain classification, Peripheral Nervous System Diseases physiopathology
- Abstract
Motivation: Nonlinear small datasets, which are characterized by low numbers of samples and very high numbers of measures, occur frequently in computational biology, and pose problems in their investigation. Unsupervised hybrid-two-phase (H2P) procedures-specifically dimension reduction (DR), coupled with clustering-provide valuable assistance, not only for unsupervised data classification, but also for visualization of the patterns hidden in high-dimensional feature space., Methods: 'Minimum Curvilinearity' (MC) is a principle that-for small datasets-suggests the approximation of curvilinear sample distances in the feature space by pair-wise distances over their minimum spanning tree (MST), and thus avoids the introduction of any tuning parameter. MC is used to design two novel forms of nonlinear machine learning (NML): Minimum Curvilinear embedding (MCE) for DR, and Minimum Curvilinear affinity propagation (MCAP) for clustering., Results: Compared with several other unsupervised and supervised algorithms, MCE and MCAP, whether individually or combined in H2P, overcome the limits of classical approaches. High performance was attained in the visualization and classification of: (i) pain patients (proteomic measurements) in peripheral neuropathy; (ii) human organ tissues (genomic transcription factor measurements) on the basis of their embryological origin., Conclusion: MC provides a valuable framework to estimate nonlinear distances in small datasets. Its extension to large datasets is prefigured for novel NMLs. Classification of neuropathic pain by proteomic profiles offers new insights for future molecular and systems biology characterization of pain. Improvements in tissue embryological classification refine results obtained in an earlier study, and suggest a possible reinterpretation of skin attribution as mesodermal., Availability: https://sites.google.com/site/carlovittoriocannistraci/home.
- Published
- 2010
- Full Text
- View/download PDF
38. Cyclic mechanical stimulation favors myosin heavy chain accumulation in engineered skeletal muscle constructs.
- Author
-
Candiani G, Riboldi SA, Sadr N, Lorenzoni S, Neuenschwander P, Montevecchi FM, and Mantero S
- Subjects
- Animals, Cell Culture Techniques, Cell Line, Mice, Muscle, Skeletal growth & development, Bioreactors, Muscle Development, Muscle, Skeletal metabolism, Myosin Heavy Chains biosynthesis, Tissue Engineering methods
- Abstract
Purpose: Since stretching plays a key role in skeletal muscle tissue development in vivo, by making use of an innovative bioreactor and a biodegradable microfibrous scaffold (DegraPol(R)) previously developed by our group, we aimed to investigate the effect of mechanical conditioning on the development of skeletal muscle engineered constructs, obtained by seeding and culturing murine skeletal muscle cells on electrospun membranes., Methods: Following 5 days of static culture, skeletal muscle constructs were transferred into the bioreactor and further cultured for 13 days, while experiencing a stretching pattern adapted from the literature to resemble mouse development and growth. Sample withdrawal occurred at the onset of cyclic stretching and after 7 and 10 days. Myosin heavy chain (MHC) accumulation in stretched constructs (D) was evaluated by Western blot analysis and immunofluorescence staining, using statically cultured samples (S) as controls., Results: Western blot analysis of MHC on dynamically (D) and statically (S) cultured constructs at different time points showed that, at day 10, the applied stretching pattern led to an eight-fold increase in myosin accumulation in cyclically stretched constructs (D) with respect to the corresponding static controls (S). These results were confirmed by immunofluorescence staining of total sarcomeric MHC., Conclusions: Since previous attempts to reproduce skeletal myogenesis in vitro mainly suffered from the difficulty of driving myoblast development into an architecturally organized array of myosin expressing myotubes, the chance of inducing MHC accumulation via mechanical conditioning represents a significant step towards the generation of a functional muscle construct for skeletal muscle tissue engineering applications.
- Published
- 2010
39. Mechanical characterization of actomyosin complex by molecular mechanics simulations.
- Author
-
Aprodu I, Soncini M, Montevecchi FM, and Redaelli A
- Subjects
- Actins metabolism, Binding Sites, Elasticity, Models, Molecular, Motor Activity, Muscle, Skeletal physiology, Protein Conformation, Thermodynamics, Actins chemistry, Actomyosin chemistry, Myosins chemistry
- Abstract
Purpose: Knowledge of the mechanical behavior of myosin and actin monomer is critical for understanding the molecular mechanism of actomyosin-based muscle and non-muscle motility. Different experimental studies concerning actomyosin interaction have been performed in vitro, but studies at the single molecule level have just begun. The aim of this study was to provide a mechanical characterization of myosin II and actin monomer using a numerical approach., Methods: The elastic properties of the two proteins involved in muscle contraction were assessed by performing stretching simulations up to 10% protein elongation using the restraining method. Interaction properties of the actomyosin complex were evaluated at eight intermolecular distances during which the entire system was left free to move., Results: According to our results, the values of the elastic modulus of the myosin motor domain and actin are 0.30 GPa, and 0.08 GPa, respectively. As for the actomyosin complex, the interaction force has a maximum value of 541.15 pN., Conclusions: Mechanical properties of molecular motors are currently being debated. Our results match a number of experimental data, therefore, supporting the idea that molecular mechanics may be a powerful tool to find a way in this complex subject.
- Published
- 2010
40. Median-modified Wiener filter provides efficient denoising, preserving spot edge and morphology in 2-DE image processing.
- Author
-
Cannistraci CV, Montevecchi FM, and Alessio M
- Subjects
- Animals, Cells, Cultured, Electrophoresis, Gel, Two-Dimensional instrumentation, Humans, Image Processing, Computer-Assisted instrumentation, Rats, Electrophoresis, Gel, Two-Dimensional methods, Image Processing, Computer-Assisted methods
- Abstract
Denoising is a fundamental early stage in 2-DE image analysis strongly influencing spot detection or pixel-based methods. A novel nonlinear adaptive spatial filter (median-modified Wiener filter, MMWF), is here compared with five well-established denoising techniques (Median, Wiener, Gaussian, and Polynomial-Savitzky-Golay filters; wavelet denoising) to suggest, by means of fuzzy sets evaluation, the best denoising approach to use in practice. Although median filter and wavelet achieved the best performance in spike and Gaussian denoising respectively, they are unsuitable for contemporary removal of different types of noise, because their best setting is noise-dependent. Vice versa, MMWF that arrived second in each single denoising category, was evaluated as the best filter for global denoising, being its best setting invariant of the type of noise. In addition, median filter eroded the edge of isolated spots and filled the space between close-set spots, whereas MMWF because of a novel filter effect (drop-off-effect) does not suffer from erosion problem, preserves the morphology of close-set spots, and avoids spot and spike fuzzyfication, an aberration encountered for Wiener filter. In our tests, MMWF was assessed as the best choice when the goal is to minimize spot edge aberrations while removing spike and Gaussian noise.
- Published
- 2009
- Full Text
- View/download PDF
41. Blood damage safety of prosthetic heart valves. Shear-induced platelet activation and local flow dynamics: a fluid-structure interaction approach.
- Author
-
Morbiducci U, Ponzini R, Nobili M, Massai D, Montevecchi FM, Bluestein D, and Redaelli A
- Subjects
- Biomechanical Phenomena, Humans, Prosthesis Failure, Reperfusion, Shear Strength, Stress, Mechanical, Thromboembolism etiology, Heart Valve Prosthesis adverse effects, Platelet Activation
- Abstract
Thromboembolism and the attendant risk of cardioembolic stroke remains an impediment to the development of prosthetic cardiovascular devices. In particular, altered haemodynamics are implicated in the acute blood cell damage that leads to thromboembolic complications, with platelet activation being the underlying mechanism for cardioemboli formation in blood flow past mechanical heart valves (MHVs) and other blood re-circulating devices. In this work, a new modeling paradigm for evaluating the cardioembolic risk of MHVs is described. In silico fluid-structure interaction (FSI) approach is used for providing a realistic representation of the flow through a bileaflet MHV model, and a Lagrangian analysis is adopted for characterizing the mechanism of mechanically induced activation of platelets by means of a mathematical model for platelet activation state prediction. Additionally, the relationship between the thromboembolic potency of the device and the local flow dynamics is quantified by giving a measure of the role played by the local streamwise and spanwise vorticity components. Our methodology indicates that (i) mechanically induced activation of platelets when passing through the valve is dependent on the phase of the cardiac cycle, where the platelet rate of activation is lower at early systole than late systole; (ii) local spanwise vorticity has greater influence on the activation of platelets (R>or=0.94) than streamwise vorticity (R>or=0.78). In conclusion, an integrated Lagrangian description of key flow characteristics could provide a more complete and quantitative picture of blood flow through MHVs and its potential to activate platelets: the proposed "comprehensive scale" approach could represent an efficient and novel assessment tool for MHV performance and may possibly lead to improved valve designs.
- Published
- 2009
- Full Text
- View/download PDF
42. A computational model for the optimization of transport phenomena in a rotating hollow-fiber bioreactor for artificial liver.
- Author
-
Consolo F, Fiore GB, Truscello S, Caronna M, Morbiducci U, Montevecchi FM, and Redaelli A
- Subjects
- Biological Transport, Clinical Trials as Topic, Oxygen analysis, Partial Pressure, Rheology, Stress, Mechanical, Ultrafiltration, Weightlessness, Bioreactors, Computer Simulation, Liver, Artificial, Rotation
- Abstract
A comprehensive computational study modelling the operation of a rotating hollow-fiber bioreactor for artificial liver (BAL) was performed to explore the interactions between the oxygenated culture medium and the cultured hepatocytes. Computational fluid dynamics investigations were carried out using two-dimensional (2D) and 3D time-dependent numerical simulations, integrating calculations of diffusion, convection, and multiphase fluid dynamics. The analysis was aimed at determining the rotational speed value of the chamber to ensure homogenous distribution of the floating microcarrier-attached aggregated cells (microCAACs) and avoid their sedimentation and excessive packing, analyzing oxygen (O(2)) delivery and cellular O(2) consumption as an index of cellular metabolic activity, and analyzing the fluid-induced mechanical stress experienced by cells. According to our results, homogeneous distribution of cells is reached at a rotational speed of 30 rpm; spreading of cellular concentration at around the initial value of 12% was limited (median = 11.97%, 5th percentile = 10.94%, 95th percentile = 13.2%), resulting in uniform suspension of microCAACs, which did not appear to be excessively packed. Mixing within the rotating fluid caused a maximum fluid-induced stress value of 0.05 Pa, which was neither endangering for liver-specific functions of cultured cells, nor causing disruption of the floating aggregates. Moreover, an inlet medium flow rate of 200 mL/m with a partial pressure of oxygen (pO(2)) value of 160 mmHg was found to guarantee an adequate O(2) supply for the hepatocytes (2.7 x 10(8) hepatocytes are simulated); under such conditions, the minimum pO(2) value (23 mmHg) is above the critical threshold value, causing the onset of cellular hypoxia (10 mmHg). We proved that numerical simulation of transport phenomena is a valuable tool for the computer-aided design of BALs, helping overcome the unsolved issues in optimizing the cell-environment conditioning procedure in rotating BALs.
- Published
- 2009
- Full Text
- View/download PDF
43. In vivo quantification of helical blood flow in human aorta by time-resolved three-dimensional cine phase contrast magnetic resonance imaging.
- Author
-
Morbiducci U, Ponzini R, Rizzo G, Cadioli M, Esposito A, De Cobelli F, Del Maschio A, Montevecchi FM, and Redaelli A
- Subjects
- Computer Simulation, Humans, Pulsatile Flow physiology, Aorta physiology, Blood Flow Velocity physiology, Blood Pressure physiology, Image Interpretation, Computer-Assisted methods, Imaging, Three-Dimensional methods, Magnetic Resonance Imaging, Cine methods, Models, Cardiovascular
- Abstract
The mechanics of blood flow in arteries plays a key role in the health of individuals. In this framework, the role played by the presence of helical flow in the human aorta is still not clear in its relation to physiology and pathology. We report here a method for quantifying helical flow in vivo employing time-resolved cine phase contrast magnetic resonance imaging to obtain the complete spatio-temporal description of the three-dimensional pulsatile blood flow patterns in aorta. The method is applied to data of one healthy volunteer. Particle traces were calculated from velocity data: to them we applied a Lagrangian-based method for helical flow quantification, the Helical Flow Index, which has been developed and evaluated in silico in order to reveal global organization of blood flow. Our results: (i) put in evidence that the systolic hemodynamics in aorta is characterized by an evolving helical flow (we quantified a 24% difference in terms of the content of helicity in the streaming blood, between mid and early systole); (ii) indicate that in the first part of the systole helicity is ascrivable mainly to the asymmetry of blood flow in the left ventricle, joined with the laterality of the aorta. In conclusion, this study shows that the quantification of helical blood flow in vivo is feasible, and it might allow detection of anomalies in the expected physiological development of helical flow in aorta and accordingly, could be used in a diagnostic/prognostic index for clinical practice.
- Published
- 2009
- Full Text
- View/download PDF
44. Blood pressure waveform analysis by means of wavelet transform.
- Author
-
De Melis M, Morbiducci U, Rietzschel ER, De Buyzere M, Qasem A, Van Bortel L, Claessens T, Montevecchi FM, Avolio A, and Segers P
- Subjects
- Adult, Carotid Artery, Common physiology, Feasibility Studies, Female, Humans, Male, Middle Aged, Pulsatile Flow physiology, Signal Processing, Computer-Assisted, Blood Pressure physiology, Models, Cardiovascular
- Abstract
The assessment of cardiovascular function by means of arterial pulse wave analysis (PWA) is well established in clinical practice. PWA is applied to study risk stratification in hypertension, with emphasis on the measurement of the augmentation index as a measure of aortic pressure wave reflections. Despite the fact that the prognostic power of PWA, in its current form, still remains to be demonstrated in the general population, there is general agreement that analysis and interpretation of the waveform might provide a deeper insight in cardiovascular pathophysiology. We propose here the use of wavelet analysis (WA) as a tool to quantify arterial pressure waveform features, with a twofold aim. First, we discuss a specific use of wavelet transform in the study of pressure waveform morphology, and its potential role in ascertaining the dynamics of temporal properties of arterial pressure waveforms. Second, we apply WA to evaluate a database of carotid artery pressure waveforms of healthy middle-aged women and men. Wavelet analysis has the potential to extract specific features (wavelet details), related to wave reflection and aortic valve closure, from a measured waveform. Analysis showed that the fifth detail, one of the waveform features extracted applying the wavelet decomposition, appeared to be the most appropriate for the analysis of carotid artery pressure waveforms. What remains to be assessed is how the information embedded in this detail can be further processed and transformed into quantitative data, and how it can be rendered useful for automated waveform classification and arterial function parameters with potential clinical applications.
- Published
- 2009
- Full Text
- View/download PDF
45. Mechanical properties of physiological and pathological models of collagen peptides investigated via steered molecular dynamics simulations.
- Author
-
Gautieri A, Vesentini S, Montevecchi FM, and Redaelli A
- Subjects
- Animals, Collagen ultrastructure, Elastic Modulus, Humans, Models, Molecular, Peptides chemistry, Peptides physiology, Stress, Mechanical, Collagen chemistry, Collagen physiology, Models, Biological, Models, Chemical, Osteogenesis Imperfecta physiopathology
- Abstract
In this work we used molecular simulations to investigate the elastic properties of collagen single chain and triple helix with the aim of understanding its features starting from first principles. We analysed ideal collagen peptides, homotrimeric and heterotrimeric collagen type I and pathological models of collagen. Triple helices were found much more rigid than single chains, thus enlightening the important role of interchain stabilizing forces, like hydrophobic interaction and hydrogen bonds. We obtained Young's moduli close to 4.5GPa for the ideal model of collagen and for the physiological heterotrimer, while the physiological homotrimer presented a Young's modulus of 2.51GPa, that can be related to a mild form of Osteogenesis Imperfecta in which only the homotrimeric form of collagen type I is produced. Otherwise, the pathological model (presenting a glycine to alanine substitution) showed an elastic modulus of 4.32GPa, thus only slightly lower than the ideal model. This suggests that this mutation only slightly affects the mechanical properties of the collagen molecule, but possibly acts on an higher scale, such as the packing of collagen fibrils.
- Published
- 2008
- Full Text
- View/download PDF
46. Mitral valve finite-element modelling from ultrasound data: a pilot study for a new approach to understand mitral function and clinical scenarios.
- Author
-
Votta E, Caiani E, Veronesi F, Soncini M, Montevecchi FM, and Redaelli A
- Subjects
- Blood Flow Velocity, Blood Pressure, Computer Simulation, Finite Element Analysis, Humans, Pilot Projects, Echocardiography methods, Image Interpretation, Computer-Assisted methods, Mitral Valve diagnostic imaging, Mitral Valve physiology, Models, Cardiovascular
- Abstract
In the current scientific literature, particular attention is dedicated to the study of the mitral valve and to comprehension of the mechanisms that lead to its normal function, as well as those that trigger possible pathological conditions. One of the adopted approaches consists of computational modelling, which allows quantitative analysis of the mechanical behaviour of the valve by means of continuum mechanics theory and numerical techniques. However, none of the currently available models realistically accounts for all of the aspects that characterize the function of the mitral valve. Here, a new computational model of the mitral valve has been developed from in vivo data, as a first step towards the development of patient-specific models for the evaluation of annuloplasty procedures. A structural finite-element model of the mitral valve has been developed to account for all of the main valvular substructures. In particular, it includes the real geometry and the movement of the annulus and papillary muscles, reconstructed from four-dimensional ultrasound data from a healthy human subject, and a realistic description of the complex mechanical properties of mitral tissues. Preliminary simulations allowed mitral valve closure to be realistically mimicked and the role of annulus and papillary muscle dynamics to be quantified.
- Published
- 2008
- Full Text
- View/download PDF
47. Doppler derived quantitative flow estimate in coronary artery bypass graft: a computational multiscale model for the evaluation of the current clinical procedure.
- Author
-
Ponzini R, Lemma M, Morbiducci U, Montevecchi FM, and Redaelli A
- Subjects
- Angiography methods, Aorta pathology, Blood Pressure, Electrocardiography methods, Equipment Design, Hemodynamics, Humans, Imaging, Three-Dimensional, Models, Biological, Reproducibility of Results, Software, Biomedical Engineering methods, Coronary Artery Bypass instrumentation, Coronary Artery Bypass methods, Ultrasonography, Doppler instrumentation, Ultrasonography, Doppler methods
- Abstract
In order to investigate the reliability of the so called mean velocity/vessel area formula adopted in clinical practice for the estimation of the flow rate using an intravascular Doppler guide wire instrumentation, a multiscale computational model was used to give detailed predictions on flow profiles within Y-shaped coronary artery bypass graft (CABG) models. At this purpose three CABG models were built from clinical patient's data and used to evaluate and compare, in each model, the computed flow rate and the flow rate estimated according to the assumption of parabolic velocity profile. A consistent difference between the exact and the estimated value of the flow rate was found in every branch of all the graft models. In this study we showed that this discrepancy in the flow rate estimation is coherent to the theory of Womersley regarding spatial velocity profiles in unsteady flow conditions. In particular this work put in evidence that the error in flow rate estimation can be reduced by using the estimation formula recently proposed by Ponzini et al. [Ponzini R, Vergara C, Redaelli A, Veneziani A. Reliable CFD-based estimation of flow rate in haemodynamics measures. Ultrasound Med Biol 2006;32(10):1545-55], accounting for the unsteady nature of blood, applicable in the clinical practice without resorting to further measurements.
- Published
- 2008
- Full Text
- View/download PDF
48. Fast membrane osmometer as alternative to freezing point and vapor pressure osmometry.
- Author
-
Grattoni A, Canavese G, Montevecchi FM, and Ferrari M
- Subjects
- Freezing, Osmosis, Pressure, Time Factors, Volatilization, Transition Temperature
- Abstract
Osmometry is an essential technique for solution analysis and the investigation of chemical and biological phenomena. Commercially available osmometers rely on the measurements of freezing point, vapor pressure, and osmotic pressure of solutions. Although vapor pressure osmometry (VPO) and freezing point osmometry (FPO) can perform rapid and inexpensive measurements, they are indirect techniques, which rely on thermodynamic assumptions, which limit their applicability. While membrane osmometry (MO) provides a potentially unlimited direct measurement of osmotic pressure and solution osmolality, the conventional technique is often time-consuming and difficult to operate. In the present work, a novel membrane osmometer is presented. The instrument significantly reduces the conventional MO measurement time and is not subject to the limitations of VPO and FPO. For this paper, the osmotic pressure of aqueous sucrose solutions was collected in a molality range 0-5.5, by way of demonstration of the new instrument. When compared with data found in the literature, the experimental data were generally in good agreement. However, differences among results from the three techniques were observed.
- Published
- 2008
- Full Text
- View/download PDF
49. The Geoform disease-specific annuloplasty system: a finite element study.
- Author
-
Votta E, Maisano F, Bolling SF, Alfieri O, Montevecchi FM, and Redaelli A
- Subjects
- Humans, Papillary Muscles surgery, Stress, Mechanical, Finite Element Analysis, Heart Valve Prosthesis Implantation methods, Mitral Valve surgery, Mitral Valve Insufficiency surgery
- Abstract
Background: Functional mitral regurgitation (FMR) is the inability of mitral leaflets to coapt due to a combination of functional and geometrical factors. Valve competence is commonly restored by undersized annuloplasty, reducing the native annulus anteroposterior dimension. In case of severe FMR, this solution may be inadequate. The use of rings specific for the correction of FMR may lead to better results., Methods: The performance of the Geoform ring, a recently designed FMR-specific prosthesis, was compared with that of a standard Physio annuloplasty ring. Finite element modeling was used to simulate dilated cardiomyopathy-related FMR and compare, at the systolic peak, the valve's pathologic condition with the postoperative scenario corresponding to both devices. Three degrees of the pathology were simulated by progressively displacing papillary muscles apically, up to 5 mm. Three ring sizes were modeled., Results: Regurgitant area, coaptation length, and stresses acting on valve structures were assessed. When the use of the Geoform was modeled, coaptation length was always longer than 7 mm. In the most unfavorable case, the regurgitant area reduction was 74% with respect to baseline, and leaflets stresses were reduced by 20% when undersizing was simulated. When Physio ring implantation was simulated, coaptation length maximum extent was equal to 4.3 mm, the maximum regurgitant area reduction was equal to 60%, and leaflet stress reduction was observed., Conclusions: Disease-specific prostheses may allow for restoration of valve competence even for significant degrees of leaflets tethering and avoid the need for aggressive undersizing, thus leading to more durable results.
- Published
- 2007
- Full Text
- View/download PDF
50. Does the Ventrica magnetic vascular positioner (MVP) for coronary artery bypass grafting significantly alter local fluid dynamics? A numeric study.
- Author
-
Morbiducci U, Lemma M, Ponzini R, Boi A, Bondavalli L, Antona C, Montevecchi FM, and Redaelli A
- Subjects
- Anastomosis, Surgical instrumentation, Automation, Blood Flow Velocity, Computer Simulation, Humans, Magnetics, Coronary Artery Bypass instrumentation, Hemorheology, Models, Cardiovascular
- Abstract
Objective: Automatic devices have been recently introduced to make the anastomosis procedure quick and efficient when creating a coronary bypass on the beating heart. However, the implantation of these devices could modify the graft configuration, consistently affecting the hemodynamics usually found in the traditional anastomosis. As local fluid dynamics could play a significant role in the onset of vessel wall pathologies, in this article a computational approach was designed to investigate flow patterns in the presence of the Ventrica magnetic vascular positioner (Ventrica MVP) device., Methods: A model of standard hand-sewn anastomosis and of automated magnetic anastomosis were constructed, and the finite volume method was used to simulate in silico realistic graft hemodynamics. Synthetic analytical descriptors -- i.e., time-averaged wall shear stress (TAWSS), oscillating shear index (OSI) and helical flow index (HFI) -- were calculated and compared for quantitative assessment of the anastomosis geometry hemodynamic performance., Results: In this case study, the same most critical region was identified for the 2 models as the one with the lowest TAWSS and the highest OSI (TAWSS=0.229, OSI=0.255 for the hand-sewn anastomosis; TAWSS=0.297, OSI=0.171 for the Ventrica MVP(R)). However, the shape of the Ventrica MVP does not induce more critical wall shear stresses, oscillating flow and damped helicity in the graft fluid dynamics, as compared with conventional anastomosis., Conclusions: We found that the use of the Ventrica MVP for the case study under investigation was not associated with more critical fluid dynamics than with conventional hand-sewn anastomosis. Thereby, the device could facilitate beating heart and minimally invasive coronary artery bypass grafting without increasing local hemodynamic-related risks of failure.
- Published
- 2007
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.