1,720,988 research outputs found
Editorial: Image-based computational approaches for personalized cardiovascular medicine: improving clinical applicability and reliability through medical imaging and experimental data
Full text linkMedical Instruments & Bio-Inspired Technolog
Building digital twins for personalized cardiovascular medicine: Advances, challenges, and future directions
Full text linkMODELING AND IMPLEMENTING A SIGNAL PERSISTENCE MANAGER FOR SHARED BIOSIGNAL STORAGE AND PROCESSING
No full text4D flow MRI-based computational analysis of blood flow in patient-specific aortic dissection
Full text linkOBJECTIVE: Computational hemodynamics studies of aortic dissections usually combine patient-specific geometries with idealized or generic boundary conditions. In this study we present a comprehensive methodology for simulations of hemodynamics in type B aortic dissection (TBAD) based on fully patient-specific BCs. METHODS: Pre-operative 4D flow magnetic resonance imaging (MRI) and Doppler-wire pressure measurements (pre- and post-operative) were acquired from a TBAD patient. These data were used to derive boundary conditions for computational modelling of flow before and after thoracic endovascular repair (TEVAR). Validations of the computational results were performed by comparing predicted flow patterns with pre-TEVAR 4D flow MRI, as well as pressures with in vivo measurements. RESULTS AND CONCLUSION: Comparison of instantaneous velocity streamlines showed a good qualitative agreement with 4D flow MRI. Quantitative comparison of predicted pressures with pressure measurements revealed a maximum difference of 11 mmHg (-9.7%). Furthermore, our model correctly predicted the reduction of true lumen pressure from 74/115 mmHg pre-TEVAR to 64/107 mmHg post-TEVAR (diastolic/systolic pressures at entry tear level), compared to the corresponding measurements of 72/118 mmHg and 64/114 mmHg. This demonstrates that pre-TEVAR 4D flow MRI can be used to tune boundary conditions for post-TEVAR hemodynamic analyses
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
A COMPARATIVE EVALUATION OF SBES and SST k-ω TRANSITION TURBULENCE MODELS IN CARDIOVASCULAR COMPUTATIONAL FLUID DYNAMICS: PATIENT-SPECIFIC LEFT VENTRICULAR ASSIST DEVICE FLOWS AND FDA'S BENCHMARK NOZZLE
No full textLeft ventricular assist devices (LVADs) are mechanical pumps that partially or fully support the function
of the left ventricle. However, around 10% of patients are estimated to experience a stroke within a year
of implantation. Computational fluid dynamics (CFD) enables detailed analysis of blood flow and
associated hemodynamic parameters, offering insights into stroke risk. Yet, in LVAD-supported aortas,
it remains unclear whether turbulence modeling is necessary to accurately capture hemodynamics. To
address this, we first assessed the performance of the Stress-Blended Eddy Simulation (SBES) model
in the FDA’s benchmark nozzle at a Reynolds number of 2000, and then compared it against SST
Transition and laminar models in three patient-specific LVAD–aorta geometries using Ansys Fluent.
For this purpose, patient-specific data and CT-derived geometries were provided by Erasmus MC.
Results from the FDA nozzle indicated that SBES overestimated jet breakdown location, although axial
velocities and shear rates remained consistent with experimental data at certain locations, the values at
jet breakdown region differ greatly, however longer simulations improve agreement. Across the patient
specific models, all three CFD approaches produced similar peak wall shear stress and velocity
distributions even in cases with high inlet flow suggesting predominantly laminar flow. These results
indicate that, while SBES can capture small-scale flow instabilities, simpler laminar or transition
models may suffice for routine LVAD–aorta simulations, thereby reducing computational cost
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Hemodynamic evaluation of aortic valve repair with the Ozaki Technique: insights from numerical models and clinical data
No full textLAUREA MAGISTRALECon l’invecchiamento della popolazione che diventa sempre più significativo, si osserva un
aumento dei pazienti affetti da malattie coronariche e delle arterie periferiche, patologie
aortiche e malattie delle valvole atrioventricolari. Per la patologia della valvola aortica,
la sostituzione valvolare è sempre stata considerata il trattamento di riferimento, preve
dendo la sostituzione della valvola aortica nativa con una protesi biologica o meccanica.
Tuttavia, la sostituzione valvolare aortica presenta ancora numerose limitazioni, come il
rapido deterioramento delle bioprotesi, l’alto rischio di complicanze legate alla terapia
anticoagulante nelle valvole meccaniche e il mismatch dimensionale, in particolare nei
pazienti giovani con anelli valvolari di piccole dimensioni.
In questo contesto, la procedura di Ozaki, nota anche come ricostruzione della valvola
aortica (AV-Rec) o neocuspidalizzazione della valvola aortica (AV-Neo), ha l’obiettivo di
ricostruire la valvola aortica utilizzando pericardio autologo trattato con glutaraldeide.
Sebbene la procedura di Ozaki presenti benefici ben identificati, rimane un tema di di
battito all’interno della comunità di chirurgia cardiaca, limitandone la diffusione per il
trattamento delle patologie valvolari.
Ciò è dovuto alla carenza di conoscenze relative alle dinamiche delle deformazioni tissutali
e al flusso sanguigno circostante per questa valvola autologa in pericardio.
Ad oggi, esistono pochi studi numerici che esaminano il legame tra le caratteristiche del
f
lusso sanguigno e la dinamica dei lembi della procedura di Ozaki.
In questo studio, la geometria aortica specifica del paziente è stata ricostruita a partire dai
dati clinici forniti dal Centro Cardiologico Monzino di Milano, mentre la valvola AV-Neo
è stata modellata virtualmente seguendo le linee guida della procedura di Ozaki.
L’analisi agli elementi finiti, la fluidodinamica computazionale e l’interazione fluido-struttura
sono state sfruttate per valutare la funzionalità della valvola dopo la riparazione, includendo
i modelli di flusso e la dinamica dei lembi, in condizioni fisiologicamente realistiche.
Il confronto dei risultati delle simulazioni con i dati di risonanza magnetica 4D-MRI è stato
utilizzato per valutare la concordanza dei principali parametri emodinamici.As the aging of the population becomes significant, we see more patients with coronary
and peripheral artery diseases, aortic diseases, and atrioventricular valve diseases. For
aortic valve disease, valve replacement has always been the gold standard treatment,
which involves the substitution of the native aortic valve with biological or mechanical
prosthesis.
However aortic valve replacement still has many limitations such as rapid deterioration
in bioprosthetic valves, high risk of anticoagulation-related complications in mechanical
valves as well as size mismatch, especially in young patients with small annuluses.
In this scenario, the Ozaki procedure, namely, Aortic Valve reconstruction (AV-Rec)
or Aortic Valve-Neocuspidization (AV-Neo), aims to reconstruct the aortic valve using
glutaraldehyde-treated autologous pericardium.
Although the Ozaki procedure has well-identified benefits, it is still a topic of debate in
the cardiac surgical community, which prevents its larger use to treat valve pathologies.
This is linked to the actual lack of knowledge regarding the dynamics of tissue deforma
tions and surrounding blood flow for this autograft pericardial valve.
So far, there is not many numerical study examining the coupling between the blood flow
characteristics and the Ozaki leaflets dynamics.
In this study patient specific aortic geometry was reconstructed from clinical data provided
by Centro Cardiologico Monzino di Milano, while the AV-Neo valve was virtually modeled
following the Ozaki procedure guidelines.
Finite Element, Computational Fluid Dynamics and Fluid Structure Interaction analysis
were exploited to evaluate post-repair valve function, including flow patterns and leaflet
dynamics, under physiologically realistic conditions.
Comparisons of simulation results with 4D-MRI data were used to assess an agreement in
key haemodynamic parameters
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