43 results on '"Sebastian, Rafael"'
Search Results
2. Impact of COVID-19 quarantine measures on electricity consumption in the central-southern zone of Chile: A quasi-experimental study
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Verdejo, Humberto, Sebastian, Rafael, Fucks, Emiliano, Vergara, Diego, Becker, Cristhian, Guzmán, Guillermo, Tobar, Francisco, and Zolezzi, Juan
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- 2024
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3. A Design-Oriented Engineering Course Involving Interactions with Stakeholders
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Quesada, Jeronimo, Calvo, Isidro, Sancho, Javier, Sebastian, Rafael, and Castro, Manuel
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Contribution: A novel project-based learning (PBL) approach applicable to diverse design-oriented engineering courses. This article reports the application results during six academic years (2012/13 to 2017/18) for electronic instrumentation (EI) course for third-year Industrial Electronic and Automation Engineering majors. Background: Engineering education should prepare students to specify, design, and validate systems interacting with stakeholders in complex professional scenarios. Intended Outcomes: The general aim of the course was to train students in the specification, design, and validation of real-world instrumentation systems, promoting the development of expertise and deep understanding of fundamental concepts and techniques. Application Design: The students, working in teams, were tasked with the specification, design, and development of different instrumentation projects. They had to exchange information about their projects with other teams and discuss design decisions, thus creating a multiple-case experience. In addition, each team acted as a provider of a different team and as a client of another team, in a circular client--provider relationship. This student-centered learning process was supported and complemented with guided teaching of fundamental concepts, principles, and techniques and with continuous evaluation, complemented with rigorous individual exams. The project activities, lectures, and problem-solving classes were coordinated to optimize the process of developing the students' understanding and expertise. Findings: Based on the academic results and the feedback from the students obtained along the years through two different anonymous surveys, it is concluded that most of the students achieved the expected learning outcomes, i.e., learning to design EI systems and dealing with stakeholders. Analyzed results proved that students were very satisfied with the methodology.
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- 2020
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4. Automatic and interpretable prediction of the site of origin in outflow tract ventricular arrhythmias: machine learning integrating electrocardiograms and clinical data.
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Bocanegra-Pérez, Álvaro J., Piella, Gemma, Sebastian, Rafael, Jimenez-Perez, Guillermo, Falasconi, Giulio, Saglietto, Andrea, Soto-Iglesias, David, Berruezo, Antonio, Penela, Diego, and Camara, Oscar
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- 2024
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5. Analysis and Modeling of Residential Energy Consumption Profiles Using Device-Level Data: A Case Study of Homes Located in Santiago de Chile.
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Verdejo, Humberto, Fucks Jara, Emiliano, Castillo, Tomas, Becker, Cristhian, Vergara, Diego, Sebastian, Rafael, Guzmán, Guillermo, Tobar, Francisco, and Zolezzi, Juan
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The advancement of technology has significantly improved energy measurement systems. Recent investment in smart meters has enabled companies and researchers to access data with the highest possible temporal disaggregation, on a minute-by-minute basis. This research aimed to obtain data with the highest possible temporal and spatial disaggregation. This was achieved through a process of energy consumption measurements for six devices within seven houses, located in different communes (counties) of the Metropolitan Region of Chile. From this process, a data panel of energy consumption of six devices was constructed for each household, observed in two temporal windows: one quarterly (750,000+ observations) and another semi-annual (1,500,000+ observations). By applying a panel data econometric model with fixed effects, calendar-temporal patterns that help explain energy consumption in each of these two windows have been studied, obtaining explanations of over 80% in some cases, and very low in others. Sensitivity analyses show that the results are robust in a short-term temporal horizon and provide a practical methodology for analyzing energy consumption determinants and load profiles with panel data. Moreover, to the authors' knowledge, these are the first results obtained with data from Chile. Therefore, the findings provide key information for the planning of production, design of energy market mechanisms, tariff regulation, and other relevant energy policies, both at local and global levels. [ABSTRACT FROM AUTHOR]
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- 2024
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6. Digital Twinning of the Human Ventricular Activation Sequence to Clinical 12-lead ECGs and Magnetic Resonance Imaging Using Realistic Purkinje Networks for in Silico Clinical Trials
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Camps, Julia, Berg, Lucas Arantes, Wang, Zhinuo Jenny, Sebastian, Rafael, Riebel, Leto Luana, Doste, Ruben, Zhou, Xin, Sachetto, Rafael, Coleman, James, Lawson, Brodie, Grau, Vicente, Burrage, Kevin, Bueno-Orovio, Alfonso, Weber, Rodrigo, and Rodriguez, Blanca
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FOS: Biological sciences ,FOS: Physical sciences ,Quantitative Biology - Tissues and Organs ,Medical Physics (physics.med-ph) ,Tissues and Organs (q-bio.TO) ,Physics - Medical Physics - Abstract
Cardiac in silico clinical trials can virtually assess the safety and efficacy of therapies using human-based modelling and simulation. These technologies can provide mechanistic explanations for clinically observed pathological behaviour. Designing virtual cohorts for in silico trials requires exploiting clinical data to capture the physiological variability in the human population. The clinical characterisation of ventricular activation and the Purkinje network is challenging, especially non-invasively. Our study aims to present a novel digital twinning pipeline that can efficiently generate and integrate Purkinje networks into human multiscale biventricular models based on subject-specific clinical 12-lead electrocardiogram and magnetic resonance recordings. Essential novel features of the pipeline are the human-based Purkinje network generation method, personalisation considering ECG R wave progression as well as QRS morphology, and translation from reduced-order Eikonal models to equivalent biophysically-detailed monodomain ones. We demonstrate ECG simulations in line with clinical data with clinical image-based multiscale models with Purkinje in four control subjects and two hypertrophic cardiomyopathy patients (simulated and clinical QRS complexes with Pearson's correlation coefficients > 0.7). Our methods also considered possible differences in the density of Purkinje myocardial junctions in the Eikonal-based inference as regional conduction velocities. These differences translated into regional coupling effects between Purkinje and myocardial models in the monodomain formulation. In summary, we demonstrate a digital twin pipeline enabling simulations yielding clinically-consistent ECGs with clinical CMR image-based biventricular multiscale models, including personalised Purkinje in healthy and cardiac disease conditions., Paper under revision
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- 2023
7. Reliability of autonomous solar-wind microgrids with battery energy storage system applied in the residential sector
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Zarate-Perez, Eliseo, Santos-Mejía, Cesar, and Sebastián, Rafael
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- 2023
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8. Autonomy evaluation model for a photovoltaic residential microgrid with a battery storage system
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Zarate-Perez, Eliseo and Sebastián, Rafael
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- 2022
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9. DURATION AND QUALITY OF SLEEP IN SPRINT AND RECOVERY PERFORMANCES AMONG ELITE SWIMMERS
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Sergio Tufik, João Paulo Pereira Rosa, Jorge José Bichara, Luísa de Sousa Nogueira Freitas, Marco Túlio de Mello, Sebastian Rafael Dias Pereira, Mário Antônio de Moura Simim, Fernanda Veruska Narciso, Andressa Silva, Sidney Cavalcante da Silva, and Dayane Ferreira Rodrigues
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medicine.medical_specialty ,Quality of sleep ,Physical Therapy, Sports Therapy and Rehabilitation ,03 medical and health sciences ,0302 clinical medicine ,Medicine ,Orthopedics and Sports Medicine ,Elite athletes ,Sleep hygiene ,biology ,business.industry ,Athletes ,Sports performance ,030229 sport sciences ,biology.organism_classification ,Sleep time ,Actigraphy ,Sprint ,Duration (music) ,Elite ,Sports medicine ,Physical therapy ,business ,Chronobiology ,RC1200-1245 ,030217 neurology & neurosurgery - Abstract
Introduction: Circadian rhythms can impact athletes' sports performance, where the plateau occurs between 15 and 21 hours. Swimming is a peculiar case, as athletes perform training and final sessions in competitions at different times, as in the Rio2016 Olympic Games for example, where the semifinal and final competitions took place from ten o'clock at night. Objectives: (1) to present the protocol of an intervention performed with elite athletes of the Brazilian swimming team during the 2016 Olympic Games in Rio; (2) to find out whether the time at which the competitions were held affected the swimming performances of these athletes during the competition. Materials and Methods: Fourteen athletes of the Brazilian swimming team (males: n= 10; 71% and females: n= 4; 29%) participated in the study. They were followed up during two preparation periods (baseline and intervention) for the 2016 Olympic Games in Rio during June and July 2016. During the competition, we recorded the Reaction Time (RT) and Competition Time (CT) of each athlete in different modalities. The intervention strategies used were light therapy and sleep hygiene. The values of RT at the starting block and CT were registered and conferred with the official results. Results: The athletes showed a decrease in the total time awake (Δ = −13%; Effect size [ES] = 1.0) and sleep latency (Δ = −33%; ES = 0.7), and an increase in total sleep time (Δ = 13%; ES = 1.1; p = 0.04) between the baseline and the period of the intervention, pre-competition. We identified an improvement in the RT (Δ = −2.2% to −1.0%; ES = 0.2 to 0.5) during the competition only for the athletes who participated in the competition finals. Conclusion: We conclude that the intervention carried out was effective in mitigating any negative influence of competition time on the RT and CT of elite athletes of the Brazilian swimming team. Level of evidence II; Prospective comparative study.
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- 2020
10. A novel method to correct repolarization time estimation from unipolar electrograms distorted by standard filtering
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Langfield, Peter, Feng, Yingjing, Bear, Laura R., Duchateau, Josselin, Sebastian, Rafael, Abell, Emma, Dubois, Remi, Labrousse, Louis, Rogier, Julien, Hocini, Meleze, Haissaguerre, Michel, Vigmond, Edward, Institut de rythmologie et modélisation cardiaque [Pessac] (IHU Liryc), Institut de Mathématiques de Bordeaux (IMB), Université Bordeaux Segalen - Bordeaux 2-Université Sciences et Technologies - Bordeaux 1 (UB)-Université de Bordeaux (UB)-Institut Polytechnique de Bordeaux (Bordeaux INP)-Centre National de la Recherche Scientifique (CNRS), Agence Nationale de la Recherche, ANR-10-IAHU-0004,LIRYC,L'Institut de Rythmologie et modélisation Cardiaque(2010), and European Project: 764738,PIC
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[SPI]Engineering Sciences [physics] ,Unipolar electrogram ,Repolarization ,CARTO ,Filtering ,Neural network - Abstract
Reliable patient-specific ventricular repolarization times (RTs) can identify regions of functional block or afterdepolarizations, indicating arrhythmogenic cardiac tissue and the risk of sudden cardiac death. Unipolar electrograms (UEs) record electric potentials, and the Wyatt method has been shown to be accurate for estimating RT from a UE. High-pass filtering is an important step in processing UEs, however, it is known to distort the T-wave phase of the UE, which may compromise the accuracy of the Wyatt method. The aim of this study was to examine the effects of high-pass filtering, and improve RT estimates derived from filtered UEs. We first generated a comprehensive set of UEs, corresponding to early and late activation and repolarization, that were then high-pass filtered with settings that mimicked the CARTO filter. We trained a deep neural network (DNN) to output a probabilistic estimation of RT and a measure of confidence, using the filtered synthetic UEs and their true RTs. Unfiltered ex-vivo human UEs were also filtered and the trained DNN used to estimate RT. Even a modest 2 Hz high-pass filter imposes a significant error on RT estimation using the Wyatt method. The DNN outperformed the Wyatt method in 62.75% of cases, and produced a significantly lower absolute error (p=8.99E−13), with a median of 16.91 ms, on 102 ex-vivo UEs. We also applied the DNN to patient UEs from CARTO, from which an RT map was computed. In conclusion, DNNs trained on synthetic UEs improve the RT estimation from filtered UEs, which leads to more reliable repolarization maps that help to identify patient-specific repolarization abnormalities.
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- 2021
11. Exocyst Is Involved in Polarized Cell Migration and Cerebral Cortical Development
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Letinic, Kresimir, Sebastian, Rafael, Toomre, Derek, and Rakic, Pasko
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- 2009
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12. Loss of Endocytic Clathrin-Coated Pits upon Acute Depletion of Phosphatidylinositol 4,5-Bisphosphate
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Zoncu, Roberto, Perera, Rushika M., Sebastian, Rafael, Nakatsu, Fubito, Chen, Hong, Balla, Tamas, Ayala, Guillermo, Toomre, Derek, and De Camilli, Pietro V.
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- 2007
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13. Training machine learning models with synthetic data improves the prediction of ventricular origin in outflow tract ventricular arrhythmias.
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Doste, Ruben, Lozano, Miguel, Jimenez-Perez, Guillermo, Mont, Lluis, Berruezo, Antonio, Penela, Diego, Camara, Oscar, and Sebastian, Rafael
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VENTRICULAR arrhythmia ,MACHINE learning ,CLASSIFICATION algorithms ,SIGNAL classification ,DATA modeling - Abstract
In order to determine the site of origin (SOO) in outflow tract ventricular arrhythmias (OTVAs) before an ablation procedure, several algorithms based on manual identification of electrocardiogram (ECG) features, have been developed. However, the reported accuracy decreases when tested with different datasets. Machine learning algorithms can automatize the process and improve generalization, but their performance is hampered by the lack of large enough OTVA databases. We propose the use of detailed electrophysiological simulations of OTVAs to train a machine learning classification model to predict the ventricular origin of the SOO of ectopic beats. We generated a synthetic database of 12-lead ECGs (2,496 signals) by running multiple simulations from the most typical OTVA SOO in 16 patient-specific geometries. Two types of input data were considered in the classification, raw and feature ECG signals. From the simulated raw 12-lead ECG, we analyzed the contribution of each lead in the predictions, keeping the best ones for the training process. For feature-based analysis, we used entropy-based methods to rank the obtained features. A cross-validation process was included to evaluate the machine learning model. Following, two clinical OTVA databases from different hospitals, including ECGs from 365 patients, were used as test-sets to assess the generalization of the proposed approach. The results show that V2 was the best lead for classification. Prediction of the SOO in OTVA, using both raw signals or features for classification, presented high accuracy values (>0.96). Generalization of the network trained on simulated data was good for both patient datasets (accuracy of 0.86 and 0.84, respectively) and presented better values than using exclusively real ECGs for classification (accuracy of 0.84 and 0.76 for each dataset). The use of simulated ECG data for training machine learning-based classification algorithms is critical to obtain good SOO predictions in OTVA compared to real data alone. The fast implementation and generalization of the proposed methodology may contribute towards its application to a clinical routine. [ABSTRACT FROM AUTHOR]
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- 2022
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14. ASTROGLIAL CB1R-A1R AND CB1R-A2AR HETEROMERS INFLUENCE MPFC SYNAPTIC FUNCTION
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Savchak, Oksana, Costa-Pinto, Sara, Sebastian, Rafael, Lillo, Alejandro, Navarro-Brugal, Gemma, Franco, Rafael, Sebastião, Ana, and Vaz, Sandra H.
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- 2023
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15. Fortgeschrittene aerodynamische Modellierung und Regelungsstrategien zur Lastreduzierung in aeroelastischen Windturbinensimulationen
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Perez-Becker, Sebastian Rafael, Paschereit, Christian Oliver, Technische Universität Berlin, Fortmann, Jens, and Barlas, Athanasios
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ddc:620 - Abstract
Increasing the size of wind turbines has been one of the most effective ways to decrease the cost of wind energy. If this trend is to continue, we need to ensure that the design loads of wind turbine components do not increase disproportionately with the turbine size. One promising way to do this is by increasing the accuracy of the aeroelastic modeling of wind turbine simulations. As aeroelastic load calculations are a critical part in determining the design loads of the turbine, increasing the model accuracy leads to more detailed load predictions and less conservative safety factors that need to be applied to compensate for model uncertainty.nAnother promising way to obtain competitive design loads for larger wind turbines is through the use of advanced control strategies that aim at reducing the design-driving loads of the turbine components. These loads are varied by nature so a combination of different actuators and strategies is required to effectively reduce them. The present work contributes to this effort in two separate but complementing ways. On the one hand, it includes a study of advanced aerodynamic models in aeroelastic simulations and their quantitative effect on wind turbine loads. On the other hand, it presents a wind turbine controller that is capable not only of performing a complete set of design load calculations but also includes advanced control strategies that mitigate design-driving loads using the generator torque, the blade pitch actuators and active trailing edge flaps distributed along the blade span. This controller is used in separate studies to reduce design-driving fatigue and extreme loads on the turbine. This dissertation is based on three papers that study different ways to achieve a load reduction. The first paper presents the turbine controller in detail. It also presents its advanced load reduction capabilities using traditional pitch and torque actuators and studies the load reduction capabilities of the individual pitch control strategy using the more accurate lifting line free vortex wake aerodynamic model in aeroelastic calculations. The second paper uses the developed controller in a study that quantifies how using more accurate aerodynamic models in aeroelastic simulations affects the loads. It compares the extreme and fatigue loads of key turbine sensors in aeroelastic simulations that are performed with the widely used blade element momentum aerodynamic model with simulations that use the lifting line free vortex wake aerodynamic model. It not only quantifies the loading differences but also finds the reasons that lead to these differences. The third paper explores the potential of active trailing edge flaps in reducing the design-driving extreme loads and critical deflections of the wind turbine blade. It considers the trailing edge flap hinge moment as a robust and readily available sensor that can be used as an input for the controller strategy. The hinge moment, in combination with other sensors, is used in a model-based observer to estimate the local inflow conditions and allow a fast response of the flap actuators. This observer is then used as part of a novel control strategy to effectively lower the extreme blade root loads and critical tip deflections. Each of the papers studies one aspect where load reduction can be obtained for larger wind turbines. This dissertation also includes suggestions for further developing and improving the respective aspects. Including them all in the design process of the next generation of wind turbines is a promising way of making this source of energy even more cost-competitive and its use more widespread. Die Vergrößerung von Windturbinen ist einer der effektivsten Wege die Stromgestehungskosten von Windenergie zu verringern. Um diesen Trend zu erhalten muss gewährleistet werden, dass die designtreibenden Lasten der Turbinenkomponenten nicht überproportional mit der Turbinengröße steigen. Eine versprechende Methode um dies zu erlangen ist die Verbesserung der aeroelastischen Modellierung in Windturbinensimulationen. Da aeroelastische Lastrechnungen eine kritische Rolle beim Design von Windturbinenkomponenten spielen, führt eine Verbesserung der Modellierung zu genaueren Designlasten und weniger konservativen Sicherheitsfaktoren bei den Lasten. Eine andere versprechende Methode um die Designlasten von großen Windturbinen zu verringern ist die Anwendung von fortgeschrittenen lastreduzierenden Regelungsstrategien. Unterschiedliche Lasten beeinflussen die Turbinenkomponenten anders und deshalb müssen auch verschiedene Aktuatoren in Betracht gezogen werden, um die desingtreibenden Lasten mehrerer Komponenten zu reduzieren. Diese Dissertation trägt zu diesem Thema in zwei separaten aber sich ergänzenden Themenbereiche bei. Einerseits beinhaltet die Arbeit eine Studie zu fortgeschrittenen aerodynamischen Modellen und deren quantitativen Effekt auf die Turbinenlasten. Andererseits präsentiert die Arbeit einen Windturbinenregler, der komplette Lastberechnungen durchführen kann und über fortgeschrittene lastreduzierende Regelungsstrategien verfügt. Diese Strategien nutzen verschiedene Aktuatoren wie Generator, Pitchaktuatoren und aktive Hinterkantenklappen und werden in unterschiedlichen Studien für die Verringerung von designtreibenden Extrem- und Ermüdungslasten verwendet. Die Arbeit basiert auf drei Veröffentlichungen die verschiedene Wege zur Lastreduzierung untersuchen. Die erste Veröffentlichung beschreibt den Windturbinenregler im Detail. Die Veröffentlichung beschreibt auch die fortgeschrittenen Lastreduktionsstrategien des entwickelten Reglers, welche auf traditionellen Aktuatoren wie die Pitchaktuatoren und dem Generatormoment beruhen. Die Lastreduktionsfähigkeit der Individual Pitch Control Strategie wird in aeroelastischen Simulationen untersucht, die das fortgeschrittene aerodynamische Modell Lifting Line Free Vortex Wake nutzen. Die zweite Veröffentlichung verwendet den Regler in einer Studie, die die Lasteffekte von fortgeschrittenen aerodynamischen Methoden in aeroelastischen Simulationen untersucht. Die Studie vergleicht Extrem- und Ermüdungslasten von wichtigen Turbinensensoren, die in aeroelastischen Simulationen mit zwei verschieden aerodynamischen Methoden berechnet worden sind. Die erste Methode ist die verbreitete Blade Element Momentum Methode. Die zweite Methode ist die fortgeschrittene Lifting Line Free Vortex Wake Methode. Die Studie quantifiziert nicht nur die Lastunterschiede sondern findet auch die Ursachen dieser Unterschiede. Die dritte Veröffentlichung untersucht das Potential von aktiven Hinterkantenklappen um designtreibende Extremlasten und kritische Durchbiegungen vom Rotorblatt zu reduzieren. Sie betrachtet das Klappengelenk-Moment als ein möglicher Regler-Sensor, der robust und bereits im Klappensystem vorhanden ist. In der Veröffentlichung wird das Klappengelenk-Moment und andere Sensoren für einen modellbasierten Beobachter genutzt, der die aerodynamischen Zustände an der Blattsektion schätzen kann. Dies ermöglicht eine schnelle Reaktion des Klappenreglers. Der Beobachter wird als Teil einer neuen Klappenstrategie verwendet, welche die Extremlasten und kritische Durchbiegung vom Rotorblatt effektiv reduziert. Die Veröffentlichungen untersuchen jeweils ein möglicher Lastreduktionsaspekt für größere Windturbinen. Diese Dissertation enthält Vorschläge, wie man diese einzelnen Aspekte verbessern kann. Alle Aspekte im Turbinen-Designprozess zu verwenden ist eine versprechende Option um die Kosten der Windenergie weiter zu reduzieren und die Nutzung dieser Technologie zu verbreiten.
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- 2021
16. Meshless Electrophysiological Modeling of Cardiac Resynchronization Therapy—Benchmark Analysis with Finite-Element Methods in Experimental Data.
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Albors, Carlos, Lluch, Èric, Gomez, Juan Francisco, Cedilnik, Nicolas, Mountris, Konstantinos A., Mansi, Tommaso, Khamzin, Svyatoslav, Dokuchaev, Arsenii, Solovyova, Olga, Pueyo, Esther, Sermesant, Maxime, Sebastian, Rafael, Morales, Hernán G., and Camara, Oscar
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CARDIAC pacing ,FINITE element method ,ELECTROPHYSIOLOGY ,KALMAN filtering - Abstract
Computational models of cardiac electrophysiology are promising tools for reducing the rates of non-response patients suitable for cardiac resynchronization therapy (CRT) by optimizing electrode placement. The majority of computational models in the literature are mesh-based, primarily using the finite element method (FEM). The generation of patient-specific cardiac meshes has traditionally been a tedious task requiring manual intervention and hindering the modeling of a large number of cases. Meshless models can be a valid alternative due to their mesh quality independence. The organization of challenges such as the CRT-EPiggy19, providing unique experimental data as open access, enables benchmarking analysis of different cardiac computational modeling solutions with quantitative metrics. We present a benchmark analysis of a meshless-based method with finite-element methods for the prediction of cardiac electrical patterns in CRT, based on a subset of the CRT-EPiggy19 dataset. A data assimilation strategy was designed to personalize the most relevant parameters of the electrophysiological simulations and identify the optimal CRT lead configuration. The simulation results obtained with the meshless model were equivalent to FEM, with the most relevant aspect for accurate CRT predictions being the parameter personalization strategy (e.g., regional conduction velocity distribution, including the Purkinje system and CRT lead distribution). [ABSTRACT FROM AUTHOR]
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- 2022
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17. An Automata-Based Cardiac Electrophysiology Simulator to Assess Arrhythmia Inducibility.
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Serra, Dolors, Romero, Pau, Garcia-Fernandez, Ignacio, Lozano, Miguel, Liberos, Alejandro, Rodrigo, Miguel, Bueno-Orovio, Alfonso, Berruezo, Antonio, and Sebastian, Rafael
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ARRHYTHMIA ,ELECTROPHYSIOLOGY ,ACTION potentials ,VENTRICULAR tachycardia ,CARDIAC arrest ,ATRIAL arrhythmias ,CELLULAR automata ,HEART conduction system - Abstract
Personalized cardiac electrophysiology simulations have demonstrated great potential to study cardiac arrhythmias and help in therapy planning of radio-frequency ablation. Its application to analyze vulnerability to ventricular tachycardia and sudden cardiac death in infarcted patients has been recently explored. However, the detailed multi-scale biophysical simulations used in these studies are very demanding in terms of memory and computational resources, which prevents their clinical translation. In this work, we present a fast phenomenological system based on cellular automata (CA) to simulate personalized cardiac electrophysiology. The system is trained on biophysical simulations to reproduce cellular and tissue dynamics in healthy and pathological conditions, including action potential restitution, conduction velocity restitution and cell safety factor. We show that a full ventricular simulation can be performed in the order of seconds, emulate the results of a biophysical simulation and reproduce a patient's ventricular tachycardia in a model that includes a heterogeneous scar region. The system could be used to study the risk of arrhythmia in infarcted patients for a large number of scenarios. [ABSTRACT FROM AUTHOR]
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- 2022
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18. Measuring spatiotemporal dependencies in bivariate temporal random sets with applications to cell biology
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Diaz, Ester, Sebastian, Rafael, Ayala, Guillermo, Diaz, Maria Elena, Zoncu, Roberto, Toomre, Derek, and Gasman, Stephane
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Fuzzy sets -- Research ,Set theory -- Research ,Monte Carlo method -- Usage ,Imaging systems -- Research - Abstract
Analyzing spatiotemporal dependencies between different types of events is highly relevant to many biological phenomena (e.g., signaling and trafficking), especially as advances in probes and microscopy have facilitated the imaging of dynamic processes in living cells. For many types of events, the segmented areas can overlap spatially and temporally, forming random clumps. In this paper, we model the binary image sequences of two different event types as a realization of a bivariate temporal random set and propose a nonparametric approach to quantify spatial and spatiotemporal interrelations using the pair correlation, cross-covariance, and the Ripley IK functions. Based on these summary statistics, we propose a randomization procedure to test independence between event types by applying random toroidal shifts and Monte Carlo tests. A simulation study assessed the performance of the proposed estimators and showed that these statistics capture the spatiotemporal dependencies accurately. The estimation of the spatiotemporal interval of interactions was also obtained. The method was successfully applied to analyze the interdependencies of several endocytic proteins using image sequences of living cells and validated the procedure as a new way to automatically quantify dependencies between proteins in a formal and robust manner. Index Terms--Random sets, Ripley IK-function, pair correlation function, covariance function, clathrin mediated endocytosis.
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- 2008
19. Gender differences in sleep patterns and sleep complaints of elite athletes
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Andressa Silva, Fernanda Veruska Narciso, João Paulo Pereira Rosa, Dayane Ferreira Rodrigues, Aline Ângela da Silva Cruz, Sérgio Tufik, Jorge José Bichara, Fernanda Viana, Jorge Jose Bichara, Sebastian Rafael Dias Pereira, Sidney Cavalcante da Silva, and Marco Túlio De Mello
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Distúrbios do sono ,Gênero e saúde ,Athletes ,Gender ,Esportes ,Atletas ,Sleep ,Sleep Disorders ,Sports ,Sono - Abstract
CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico FAPEMIG - Fundação de Amparo à Pesquisa do Estado de Minas Gerais CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior Outra Agência OBJECTIVE: The present study aimed to investigate the gender differences for sleep complaints, patterns and disorders of elite athletes during preparation for the Rio 2016 Olympic Games. METHODS: The study included 146 athletes from the Brazilian Olympic Team (male: n=86; 59%; female: n=60; 41%). The assessment of the Olympic athletes’ sleep took place in 2015, during the preparation period for the Rio Olympic Games. The athletes underwent a single polysomnography (PSG) evaluation. Sleep specialists evaluated the athletes and asked about their sleep complaints during a clinical consultation. In this evaluation week, the athletes did not take part in any training or competitions. RESULTS: The prevalence of sleep complaints was 53% of the athletes during the medical consultation, the most prevalent being insufficient sleep/waking up tired (32%), followed by snoring (21%) and insomnia (19.2%). In relation to the sleep pattern findings, the men had significantly higher sleep latency and wake after sleep onset than the women (p=0.004 and p=0.002, respectively). The sleep efficiency and sleep stages revealed that men had a lower percentage of sleep efficiency and slow wave sleep than the women (p=0.001 and p=0.05, respectively). CONCLUSION: Most athletes reported some sleep complaints, with men reporting more sleep complaints than women in the clinical evaluation. The PSG showed that 36% of all athletes had a sleep disorder with a greater reduction in sleep quality in men than in women.
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- 2019
20. Analysis of spatially and temporally overlapping events with application to image sequences
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Ayala, Guillermo, Sebastian, Rafael, Diaz, Maria Elena, Diaz, Ester, Zoncu, Roberto, and Toomre, Derek
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Reflection (Optics) -- Research ,Algebra, Boolean -- Analysis ,Fluorescence microscopy -- Usage ,Functional analysis - Abstract
Counting spatially and temporally overlapping events in image sequences and estimating their shape-size and duration features are important issues in some applications. We propose a stochastic model, a particular case of the nonisotropic 3D Boolean model, for performing this analysis: the temporal Boolean model. Some probabilistic properties are derived and a methodology for parameter estimation from time-lapse image sequences is proposed using an explicit treatment of the temporal dimension. We estimate the mean number of germs per unit area and time, the mean grain size and the duration distribution. A wide simulation study in order to assess the proposed estimators showed promising results. The model was applied on biological image sequences of invivo cells in order to estimate new parameters such as the mean number and duration distribution of endocytic events. Our results show that the proposed temporal Boolean model is effective for obtaining information about dynamic processes which exhibit short-lived, but spatially and temporally overlapping events. Index Terms--Temporal Boolean model, 3D Boolean models, germ-grain models, coverage processes, functional data analysis, endocytosis, total internal reflection fluorescence microscopy.
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- 2006
21. Deciphering subcellular processes in live imaging datasets via dynamic probabilistic networks
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Letinic, Kresimir, Sebastian, Rafael, Barthel, Andrew, and Toomre, Derek
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- 2010
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22. Estimation of Personalized Minimal Purkinje Systems From Human Electro-Anatomical Maps.
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Barber, Fernando, Langfield, Peter, Lozano, Miguel, Garcia-Fernandez, Ignacio, Duchateau, Josselin, Hocini, Meleze, Haissaguerre, Michel, Vigmond, Edward, and Sebastian, Rafael
- Subjects
CARDIAC contraction ,ATRIAL flutter ,CATHETER ablation ,ENDOCARDIUM - Abstract
The Purkinje system is a heart structure responsible for transmitting electrical impulses through the ventricles in a fast and coordinated way to trigger mechanical contraction. Estimating a patient-specific compatible Purkinje Network from an electro-anatomical map is a challenging task, that could help to improve models for electrophysiology simulations or provide aid in therapy planning, such as radiofrequency ablation. In this study, we present a methodology to inversely estimate a Purkinje network from a patient’s electro-anatomical map. First, we carry out a simulation study to assess the accuracy of the method for different synthetic Purkinje network morphologies and myocardial junction densities. Second, we estimate the Purkinje network from a set of 28 electro-anatomical maps from patients, obtaining an optimal conduction velocity in the Purkinje network of 1.95 ± 0.25 m/s, together with the location of their Purkinje-myocardial junctions, and Purkinje network structure. Our results showed an average local activation time error of 6.8±2.2 ms in the endocardium. Finally, using the personalized Purkinje network, we obtained correlations higher than 0.85 between simulated and clinical 12-lead ECGs. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
23. A Design-Oriented Engineering Course Involving Interactions With Stakeholders.
- Author
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Quesada, Jeronimo, Calvo, Isidro, Sancho, Javier, Sebastian, Rafael, and Castro, Manuel
- Subjects
ENGINEERING education ,STUDENT-centered learning ,LEARNING ,ENGINEERING ,CONCEPT learning - Abstract
Contribution: A novel project-based learning (PBL) approach applicable to diverse design-oriented engineering courses. This article reports the application results during six academic years (2012/13 to 2017/18) for electronic instrumentation (EI) course for third-year Industrial Electronic and Automation Engineering majors. Background: Engineering education should prepare students to specify, design, and validate systems interacting with stakeholders in complex professional scenarios. Intended Outcomes: The general aim of the course was to train students in the specification, design, and validation of real-world instrumentation systems, promoting the development of expertise and deep understanding of fundamental concepts and techniques. Application Design: The students, working in teams, were tasked with the specification, design, and development of different instrumentation projects. They had to exchange information about their projects with other teams and discuss design decisions, thus creating a multiple-case experience. In addition, each team acted as a provider of a different team and as a client of another team, in a circular client–provider relationship. This student-centered learning process was supported and complemented with guided teaching of fundamental concepts, principles, and techniques and with continuous evaluation, complemented with rigorous individual exams. The project activities, lectures, and problem-solving classes were coordinated to optimize the process of developing the students’ understanding and expertise. Findings: Based on the academic results and the feedback from the students obtained along the years through two different anonymous surveys, it is concluded that most of the students achieved the expected learning outcomes, i.e., learning to design EI systems and dealing with stakeholders. Analyzed results proved that students were very satisfied with the methodology. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
24. In silico pace-mapping: prediction of left vs. right outflow tract origin in idiopathic ventricular arrhythmias with patient-specific electrophysiological simulations.
- Author
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Doste, Ruben, Sebastian, Rafael, Gomez, Juan Francisco, Soto-Iglesias, David, Alcaine, Alejandro, Mont, Lluis, Berruezo, Antonio, Penela, Diego, and Camara, Oscar
- Subjects
ARRHYTHMIA diagnosis ,COMPUTER simulation ,RESEARCH ,RESEARCH methodology ,CATHETER ablation ,MEDICAL cooperation ,EVALUATION research ,VENTRICULAR tachycardia ,HEART ventricles ,COMPARATIVE studies ,ELECTROCARDIOGRAPHY - Abstract
Aims: A pre-operative non-invasive identification of the site of origin (SOO) of outflow tract ventricular arrhythmias (OTVAs) is important to properly plan radiofrequency ablation procedures. Although some algorithms based on electrocardiograms (ECGs) have been developed to predict left vs. right ventricular origins, their accuracy is still limited, especially in complex anatomies. The aim of this work is to use patient-specific electrophysiological simulations of the heart to predict the SOO in OTVA patients.Methods and Results: An in silico pace-mapping procedure was designed and used on 11 heart geometries, generating for each case simulated ECGs from 12 clinically plausible SOO. Subsequently, the simulated ECGs were compared with patient ECG data obtained during the clinical tachycardia using the 12-lead correlation coefficient (12-lead ρ). Left ventricle (LV) vs. right ventricle (RV) SOO was estimated by computing the LV/RV ratio for each patient, obtained by dividing the average 12-lead ρ value of the LV- and RV-SOO simulated ECGs, respectively. Simulated ECGs that had virtual sites close to the ablation points that stopped the arrhythmia presented higher correlation coefficients. The LV/RV ratio correctly predicted LV vs. RV SOO in 10/11 cases; 1.07 vs. 0.93 P < 0.05 for 12-lead ρ.Conclusion: The obtained results demonstrate the potential of the developed in silico pace-mapping technique to complement standard ECG for the pre-operative planning of complex ventricular arrhythmias. [ABSTRACT FROM AUTHOR]- Published
- 2020
- Full Text
- View/download PDF
25. Urban scale air quality modelling using detailed traffic emissions estimates
- Author
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Oxana Tchepel, Daniela Dias, Jorge Humberto Amorim, Margarida C. Coelho, Sebastian Rafael Dias Pereira, Tânia Fontes, Carlos Borrego, Cláudia Pimentel, Jorge M. Bandeira, Paulo Fernandes, Sandra Rafael, and E. Sá
- Subjects
Atmospheric Science ,010504 meteorology & atmospheric sciences ,Meteorology ,Gaussian ,Filter (signal processing) ,010501 environmental sciences ,Atmospheric dispersion modeling ,01 natural sciences ,Vehicle-specific power ,symbols.namesake ,Transmission (telecommunications) ,symbols ,Environmental science ,Time series ,Gaussian network model ,Air quality index ,0105 earth and related environmental sciences ,General Environmental Science - Abstract
The atmospheric dispersion of NO x and PM10 was simulated with a second generation Gaussian model over a medium-size south-European city. Microscopic traffic models calibrated with GPS data were used to derive typical driving cycles for each road link, while instantaneous emissions were estimated applying a combined Vehicle Specific Power/Co-operative Programme for Monitoring and Evaluation of the Long-range Transmission of Air Pollutants in Europe (VSP/EMEP) methodology. Site-specific background concentrations were estimated using time series analysis and a low-pass filter applied to local observations. Air quality modelling results are compared against measurements at two locations for a 1 week period. 78% of the results are within a factor of two of the observations for 1-h average concentrations, increasing to 94% for daily averages. Correlation significantly improves when background is added, with an average of 0.89 for the 24 h record. The results highlight the potential of detailed traffic and instantaneous exhaust emissions estimates, together with filtered urban background, to provide accurate input data to Gaussian models applied at the urban scale.
- Published
- 2016
26. Changes in the spatial distribution of the Purkinje network after acute myocardial infarction in the pig.
- Author
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Garcia-Bustos, Victor, Sebastian, Rafael, Izquierdo, Maite, Rios-Navarro, César, Bodí, Vicente, Chorro, Francisco Javier, and Ruiz-Sauri, Amparo
- Subjects
- *
PURKINJE cells , *MYOCARDIAL infarction , *HEART conduction system , *HEART cells , *VENTRICULAR tachycardia - Abstract
Purkinje cells (PCs) are more resistant to ischemia than myocardial cells, and are suspected to participate in ventricular arrhythmias following myocardial infarction (MI). Histological studies afford little evidence on the behavior and adaptation of PCs in the different stages of MI, especially in the chronic stage, and no quantitative data have been reported to date beyond subjective qualitative depictions. The present study uses a porcine model to present the first quantitative analysis of the distal cardiac conduction system and the first reported change in the spatial distribution of PCs in three representative stages of MI: an acute model both with and without reperfusion; a subacute model one week after reperfusion; and a chronic model one month after reperfusion. Purkinje cells are able to survive after 90 minutes of ischemia and subsequent reperfusion to a greater extent than cardiomyocytes. A decrease is observed in the number of PCs, which suffer reversible subcellular alterations such as cytoplasm vacuolization, together with redistribution from the mesocardium—the main localization of PCs in the heart of ungulate species—towards the endocardium and perivascular epicardial areas. However, these changes mainly occur during the first week after ischemia and reperfusion, and are maintained in the chronic stages. This anatomical substrate can explain the effectiveness of endo-epicardial catheter ablation of monomorphic ventricular tachycardias in the chronic scar after infarction, and sets a basis for further electrophysiological and molecular studies, and future therapeutic strategies. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
27. Optimization of Lead Placement in the Right Ventricle During Cardiac Resynchronization Therapy. A Simulation Study.
- Author
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Carpio, Edison F., Gomez, Juan F., Sebastian, Rafael, Lopez-Perez, Alejandro, Castellanos, Eduardo, Almendral, Jesus, Ferrero, Jose M., and Trenor, Beatriz
- Subjects
RIGHT heart ventricle ,CARDIAC pacing ,HEART failure patients ,PATIENT-ventilator dyssynchrony ,LEFT heart ventricle - Abstract
Patients suffering from heart failure and left bundle branch block show electrical ventricular dyssynchrony causing an abnormal blood pumping. Cardiac resynchronization therapy (CRT) is recommended for these patients. Patients with positive therapy response normally present QRS shortening and an increased left ventricle (LV) ejection fraction. However, around one third do not respond favorably. Therefore, optimal location of pacing leads, timing delays between leads and/or choosing related biomarkers is crucial to achieve the best possible degree of ventricular synchrony during CRT application. In this study, computational modeling is used to predict the optimal location and delay of pacing leads to improve CRT response. We use a 3D electrophysiological computational model of the heart and torso to get insight into the changes in the activation patterns obtained when the heart is paced from different regions and for different atrioventricular and interventricular delays. The model represents a heart with left bundle branch block and heart failure, and allows a detailed and accurate analysis of the electrical changes observed simultaneously in the myocardium and in the QRS complex computed in the precordial leads. Computational simulations were performed using a modified version of the O'Hara et al. action potential model, the most recent mathematical model developed for human ventricular electrophysiology. The optimal location for the pacing leads was determined by QRS maximal reduction. Additionally, the influence of Purkinje system on CRT response was assessed and correlation analysis between several parameters of the QRS was made. Simulation results showed that the right ventricle (RV) upper septum near the outflow tract is an alternative location to the RV apical lead. Furthermore, LV endocardial pacing provided better results as compared to epicardial stimulation. Finally, the time to reach the 90% of the QRS area was a good predictor of the instant at which 90% of the ventricular tissue was activated. Thus, the time to reach the 90% of the QRS area is suggested as an additional index to assess CRT effectiveness to improve biventricular synchrony. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
28. Atrial Fibrosis Hampers Non-invasive Localization of Atrial Ectopic Foci From Multi-Electrode Signals: A 3D Simulation Study.
- Author
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Godoy, Eduardo Jorge, Lozano, Miguel, García-Fernández, Ignacio, Ferrer-Albero, Ana, Sebastian, Rafael, MacLeod, Rob, and Saiz, Javier
- Subjects
ARRHYTHMIA diagnosis ,FIBROSIS ,BIOELECTRONICS ,ELECTROCARDIOGRAPHY ,ARRHYTHMIA treatment ,DIAGNOSIS ,THERAPEUTICS - Abstract
Introduction: Focal atrial tachycardia is commonly treated by radio frequency ablation with an acceptable long-term success. Although the location of ectopic foci tends to appear in specific hot-spots, they can be located virtually in any atrial region. Multi-electrode surface ECG systems allow acquiring dense body surface potential maps (BSPM) for non-invasive therapy planning of cardiac arrhythmia. However, the activation of the atria could be affected by fibrosis and therefore biomarkers based on BSPM need to take these effects into account. We aim to analyze the effect of fibrosis on a BSPM derived index, and its potential application to predict the location of ectopic foci in the atria. Methodology: We have developed a 3D atrial model that includes 5 distributions of patchy fibrosis in the left atrium at 5 different stages. Each stage corresponds to a different amount of fibrosis that ranges from 2 to 40%. The 25 resulting 3D models were used for simulation of Focal Atrial Tachycardia (FAT), triggered from 19 different locations described in clinical studies. BSPM were obtained for all simulations, and the body surface potential integral maps (BSPiM) were calculated to describe atrial activations. A machine learning (ML) pipeline using a supervised learning model and support vector machine was developed to learn the BSPM patterns of each of the 475 activation sequences and relate them to the origin of the FAT source. Results: Activation maps for stages with more than 15% of fibrosis were greatly affected, producing conduction blocks and delays in propagation. BSPiMs did not always cluster into non-overlapped groups since BSPiMs were highly altered by the conduction blocks. From stage 3 (15% fibrosis) the BSPiMs showed differences for ectopic beats placed around the area of the pulmonary veins. Classification results were mostly above 84% for all the configurations studied when a large enough number of electrodes were used to map the torso. However, the presence of fibrosis increases the area of the ectopic focus location and therefore decreases the utility for the electrophysiologist. Conclusions: The results indicate that the proposed ML pipeline is a promising methodology for non-invasive ectopic foci localization from BSPM signal even when fibrosis is present. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
29. Factors affecting basket catheter detection of real and phantom rotors in the atria: A computational study.
- Author
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Martinez-Mateu, Laura, Romero, Lucia, Ferrer-Albero, Ana, Sebastian, Rafael, Rodríguez Matas, José F., Jalife, José, Berenfeld, Omer, and Saiz, Javier
- Subjects
ATRIAL fibrillation ,CATHETERS ,ELECTROPHYSIOLOGY ,ATRIAL arrhythmias ,DRUG delivery devices - Abstract
Anatomically based procedures to ablate atrial fibrillation (AF) are often successful in terminating paroxysmal AF. However, the ability to terminate persistent AF remains disappointing. New mechanistic approaches use multiple-electrode basket catheter mapping to localize and target AF drivers in the form of rotors but significant concerns remain about their accuracy. We aimed to evaluate how electrode-endocardium distance, far-field sources and inter-electrode distance affect the accuracy of localizing rotors. Sustained rotor activation of the atria was simulated numerically and mapped using a virtual basket catheter with varying electrode densities placed at different positions within the atrial cavity. Unipolar electrograms were calculated on the entire endocardial surface and at each of the electrodes. Rotors were tracked on the interpolated basket phase maps and compared with the respective atrial voltage and endocardial phase maps, which served as references. Rotor detection by the basket maps varied between 35–94% of the simulation time, depending on the basket’s position and the electrode-to-endocardial wall distance. However, two different types of phantom rotors appeared also on the basket maps. The first type was due to the far-field sources and the second type was due to interpolation between the electrodes; increasing electrode density decreased the incidence of the second but not the first type of phantom rotors. In the simulations study, basket catheter-based phase mapping detected rotors even when the basket was not in full contact with the endocardial wall, but always generated a number of phantom rotors in the presence of only a single real rotor, which would be the desired ablation target. Phantom rotors may mislead and contribute to failure in AF ablation procedures. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
30. Uncoupling of dynamin polymerization and GTPase activity revealed by the conformation-specific nanobody dynab.
- Author
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Galli, Valentina, Sebastian, Rafael, Moutel, Sandrine, Ecard, Jason, Perez, Franck, and Roux, Aurélien
- Subjects
- *
DYNAMIN (Genetics) , *GUANOSINE triphosphatase , *FISSION (Asexual reproduction) , *BIOLOGICAL membranes , *HYDROLYSIS - Abstract
Dynamin is a large GTPase that forms a helical collar at the neck of endocytic pits, and catalyzes membrane fission (Schmid and Frolov, 2011; Ferguson and De Camilli, 2012). Dynamin fission reaction is strictly dependent on GTP hydrolysis, but how fission is mediated is still debated (Antonny et al., 2016): GTP energy could be spent in membrane constriction required for fission, or in disassembly of the dynamin polymer to trigger fission. To follow dynamin GTP hydrolysis at endocytic pits, we generated a conformation-specific nanobody called dynab, that binds preferentially to the GTP hydrolytic state of dynamin-1. Dynab allowed us to follow the GTPase activity of dynamin-1 in real-time. We show that in fibroblasts, dynamin GTP hydrolysis occurs as stochastic bursts, which are randomly distributed relatively to the peak of dynamin assembly. Thus, dynamin disassembly is not coupled to GTPase activity, supporting that the GTP energy is primarily spent in constriction. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
31. Mechanical dyssynchrony indices from an electrophysiological contact mapping system predict response to CRT
- Author
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Camara, Oscar, Bijnens, Bart H., Silva, Etel, Andreu, David, Oeltze, Steffen, Romero, Daniel, De Craene, Mathieu, Tamborero, David, Sebastian, Rafael, Mont, Lluis, Sitges, Marta, Frangi, Alejandro, Monteil, Alain, Center for Computational Imaging and Simulation Technologies in Biomedicine (CISTIB), Universitat Pompeu Fabra [Barcelona] (UPF), Biomedical Research Networking Center in Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Instituto de Salud Carlos III [Madrid] (ISC)-ministerio de ciencia e innovacion, Institució Catalana de Recerca i Estudis Avançats (ICREA), Cardiology Department, Thorax Clinic Institute, Hospital Cliınic, Institut d'Investigacions Biomèdiques [Barcelona], Universitat de Barcelona (UB), Institute of Simulation and Graphics [Magdeburg], Otto-von-Guericke University [Magdeburg] (OVGU), Session 03 : Perfusion, and Contractility and Heart Failure
- Subjects
genetic structures ,[INFO.INFO-IM]Computer Science [cs]/Medical Imaging ,[INFO.INFO-IM] Computer Science [cs]/Medical Imaging ,cardiac resynchronization therapy ,Electrophysiological contact mapping system ,left bundle branch block ,cardiovascular diseases ,septal flash motion - Abstract
International audience; We present a methodology to extract mechanical dyssynchrony indices from an electrophysiological (EP) contact mapping system that was applied to a database of ten patients undergoing Cardiac Resynchronization Therapy (CRT), before and after the therapy. The mechanical dyssynchrony indices were obtained after post-processing high temporal resolution data recorded at several endocardial positions with the measuring catheter of the EP system. Velocity profiles of these catheter trajectories were analyzed to identify abnormal patterns of motion such as septal flash, whose presence is strongly related to a positive response to CRT in patients with left bundle branch block. Septal flash motion was identified in four cases, which was qualitatively validated by visual inspection of imaging data, and a strong correlation with response to CRT was observed a posteriori. Finally, the effect of biventricular pacing was clearly observable by a substantial reduction of the septal flash motion.
- Published
- 2009
32. Non-invasive localization of atrial ectopic beats by using simulated body surface P-wave integral maps.
- Author
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Ferrer-Albero, Ana, Godoy, Eduardo J., Lozano, Miguel, Martínez-Mateu, Laura, Atienza, Felipe, Saiz, Javier, and Sebastian, Rafael
- Subjects
P-waves (Electrocardiography) ,NONINVASIVE diagnostic tests ,ATRIAL arrhythmias ,BODY surface mapping ,ESTIMATION theory ,THERAPEUTICS - Abstract
Non-invasive localization of continuous atrial ectopic beats remains a cornerstone for the treatment of atrial arrhythmias. The lack of accurate tools to guide electrophysiologists leads to an increase in the recurrence rate of ablation procedures. Existing approaches are based on the analysis of the P-waves main characteristics and the forward body surface potential maps (BSPMs) or on the inverse estimation of the electric activity of the heart from those BSPMs. These methods have not provided an efficient and systematic tool to localize ectopic triggers. In this work, we propose the use of machine learning techniques to spatially cluster and classify ectopic atrial foci into clearly differentiated atrial regions by using the body surface P-wave integral map (BSPiM) as a biomarker. Our simulated results show that ectopic foci with similar BSPiM naturally cluster into differentiated non-intersected atrial regions and that new patterns could be correctly classified with an accuracy of 97% when considering 2 clusters and 96% for 4 clusters. Our results also suggest that an increase in the number of clusters is feasible at the cost of decreasing accuracy. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
33. Analysis of Microstructure of the Cardiac Conduction System Based on Three-Dimensional Confocal Microscopy.
- Author
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Romero, Daniel, Camara, Oscar, Sachse, Frank, and Sebastian, Rafael
- Subjects
HEART conduction system ,MYOCARDIUM physiology ,PURKINJE cells ,CELL junctions ,MICROSTRUCTURE ,CONFOCAL microscopy ,THREE-dimensional imaging - Abstract
The specialised conducting tissues present in the ventricles are responsible for the fast distribution of the electrical impulse from the atrio-ventricular node to regions in the subendocardial myocardium. Characterisation of anatomical features of the specialised conducting tissues in the ventricles is highly challenging, in particular its most distal section, which is connected to the working myocardium via Purkinje-myocardial junctions. The goal of this work is to characterise the architecture of the distal section of the Purkinje network by differentiating Purkinje cells from surrounding tissue, performing a segmentation of Purkinje fibres at cellular scale, and mathematically describing its morphology and interconnections. Purkinje cells from rabbit hearts were visualised by confocal microscopy using wheat germ agglutinin labelling. A total of 16 3D stacks including labeled Purkinje cells were collected, and semi-automatically segmented. State-of-the-art graph metrics were applied to estimate regional and global features of the Purkinje network complexity. Two types of cell types, tubular and star-like, were characterised from 3D segmentations. The analysis of 3D imaging data confirms the previously suggested presence of two types of Purkinje-myocardium connections, a 2D interconnection sheet and a funnel one, in which the narrow side of a Purkinje fibre connect progressively to muscle fibres. The complex network analysis of interconnected Purkinje cells showed no small-world connectivity or assortativity properties. These results might help building more realistic computational PK systems at high resolution levels including different cell configurations and shapes. Better knowledge on the organisation of the network might help in understanding the effects that several treatments such as radio-frequency ablation might have when the PK system is disrupted locally. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
34. Three-dimensional cardiac computational modelling: methods, features and applications.
- Author
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Lopez-Perez, Alejandro, Sebastian, Rafael, and Ferrero, Jose M.
- Abstract
The combination of computational models and biophysical simulations can help to interpret an array of experimental data and contribute to the understanding, diagnosis and treatment of complex diseases such as cardiac arrhythmias. For this reason, three-dimensional (3D) cardiac computational modelling is currently a rising field of research. The advance of medical imaging technology over the last decades has allowed the evolution from generic to patient-specific 3D cardiac models that faithfully represent the anatomy and different cardiac features of a given alive subject. Here we analyse sixty representative 3D cardiac computational models developed and published during the last fifty years, describing their information sources, features, development methods and online availability. This paper also reviews the necessary components to build a 3D computational model of the heart aimed at biophysical simulation, paying especial attention to cardiac electrophysiology (EP), and the existing approaches to incorporate those components. We assess the challenges associated to the different steps of the building process, from the processing of raw clinical or biological data to the final application, including image segmentation, inclusion of substructures and meshing among others. We briefly outline the personalisation approaches that are currently available in 3D cardiac computational modelling. Finally, we present examples of several specific applications, mainly related to cardiac EP simulation and model-based image analysis, showing the potential usefulness of 3D cardiac computational modelling into clinical environments as a tool to aid in the prevention, diagnosis and treatment of cardiac diseases. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
35. Characterization and Modeling of the Peripheral Cardiac Conduction System.
- Author
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Sebastian, Rafael, Zimmerman, Viviana, Romero, Daniel, Sanchez-Quintana, Damian, and Frangi, Alejandro F.
- Subjects
- *
HEART conduction system , *HEART pathophysiology , *HEART anatomy , *PURKINJE cells , *MATHEMATICAL models , *HEART cells , *ELECTROPHYSIOLOGY - Abstract
The development of biophysical models of the heart has the potential to get insights in the patho-physiology of the heart, which requires to accurately modeling anatomy and function. The electrical activation sequence of the ventricles depends strongly on the cardiac conduction system (CCS). Its morphology and function cannot be observed in vivo, and therefore data available come from histological studies. We present a review on data available of the peripheral CCS including new experiments. In order to build a realistic model of the CCS we designed a procedure to extract morphological characteristics of the CCS from stained calf tissue samples. A CCS model personalized with our measurements has been built using L-systems. The effect of key unknown parameters of the model in the electrical activation of the left ventricle has been analyzed. The CCS models generated share the main characteristics of observed stained Purkinje networks. The timing of the simulated electrical activation sequences were in the physiological range for CCS models that included enough density of PMJs. These results show that this approach is a potential methodology for collecting knowledge-domain data and build improved CCS models of the heart automatically. [ABSTRACT FROM PUBLISHER]
- Published
- 2013
- Full Text
- View/download PDF
36. Construction of a Computational Anatomical Model of the Peripheral Cardiac Conduction System.
- Author
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Sebastian, Rafael, Zimmerman, Viviana, Romero, Daniel, and Frangi, Alejandro F.
- Subjects
- *
HEART conduction system , *HUMAN anatomy , *COMPUTATIONAL biology , *L systems , *MATHEMATICAL statistics , *STOCHASTIC analysis , *BIOLOGICAL systems , *MATHEMATICAL models , *ELECTROPHYSIOLOGY , *COMPUTER software - Abstract
A methodology is presented here for automatic construction of a ventricular model of the cardiac conduction system (CCS), which is currently a missing block in many multiscale cardiac electromechanic models. It includes the His bundle, left bundle branches, and the peripheral CCS. The algorithm is fundamentally an enhancement of a rule-based method known as the Lindenmayer systems (L-systems). The generative procedure has been divided into three consecutive independent stages, which subsequently build the CCS from proximal to distal sections. Each stage is governed by a set of user parameters together with anatomical and physiological constrains to direct the generation process and adhere to the structural observations derived from histology studies. Several parameters are defined using statistical distributions to introduce stochastic variability in the models. The CCS built with this approach can generate electrical activation sequences with physiological characteristics. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
37. Interaction of Specialized Cardiac Conduction System With Antiarrhythmic Drugs: A Simulation Study.
- Author
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Dux-Santoy, Lydia, Sebastian, Rafael, Felix-Rodriguez, Jose, Ferrero, Jose Maria, and Saiz, Javier
- Subjects
- *
HEART conduction system , *MYOCARDIAL depressants , *BIOMEDICAL engineering , *ELECTROPHYSIOLOGY , *BIOLOGICAL systems , *MATHEMATICAL models , *DRUGS , *HEART diseases - Abstract
The use of antiarrhythmic drugs is common to treat heart rhythm disorders. Computational modeling and simulation are promising tools that could be used to investigate the effects of specific drugs on cardiac electrophysiology. In this paper, we study the multiscale effects of dofetilide, a drug that blocks IKr, from cellular to organ level paying special attention to its effect on heart structures, in particular the specialized cardiac conduction system (CCS). We include a model of the CCS in a patient-specific anatomical ventricular model and study the drug effects in simulations with and without a CCS. Results confirmed the expected effects of dofetilide at cellular level, increasing the action potential duration, and at organ level, prolonging the QT segment. Notable differences are shown between models with and without the CCS on action potential duration distributions. These techniques show the importance of heart heterogeneity and the global effects of the interaction of drugs with cardiac structures. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
38. Fast Multiscale Modeling of Cardiac Electrophysiology Including Purkinje System.
- Author
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Pashaei, Ali, Romero, Daniel, Sebastian, Rafael, Camara, Oscar, and Frangi, Alejandro F.
- Subjects
ELECTROPHYSIOLOGY ,HEART conduction system ,MYOCARDIUM ,CARDIOGRAPHIC tomography ,HEART models ,PURKINJE cells ,MULTISCALE modeling ,COMPUTER simulation - Abstract
In this paper, we present a modeling methodology to couple the cardiac conduction system to cardiac myocytes through a model of Purkinje-ventricular junctions to yield fast and realistic electrical activation of the ventricles. A patient-specific biventricular geometry is obtained from processing computed tomography scan data. A one-manifold implementation of the fast marching method based on Eikonal-type equations is used for modeling heart electrophysiology, which facilitates the multiscale 1-D–3-D coupling at very low computational costs. The method is illustrated in in-silico experiments where we analyze and compare alternative pacing strategies on the same patient-specific anatomy. We also show very good agreement between the results from the proposed approach and more detailed and comprehensive biophysical models for modeling cardiac electrophysiology. The effect of atrioventricular delay on the distribution of activation time in myocardium is studied with two experiments. Given the reasonable computational times and realistic activation sequences provided by our method, it can have an important clinical impact on the selection of optimal implantation sites of pacing leads or placement of ablation catheter’s tip in the context of cardiac rhythm management therapies. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
39. Image Denoising Using Adaptive and Overlapped Average Filtering and Mixed-Pooling Attention Refinement Networks.
- Author
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Lin, Ming-Hao, Hou, Zhi-Xiang, Cheng, Kai-Han, Wu, Chin-Hsien, Peng, Yan-Tsung, and Sebastian, Rafael
- Subjects
IMAGE denoising ,IMAGE analysis ,IMAGE recognition (Computer vision) ,SMARTPHONES ,ATTENTION ,PIXELS - Abstract
Cameras are essential parts of portable devices, such as smartphones and tablets. Most people have a smartphone and can take pictures anywhere and anytime to record their lives. However, these pictures captured by cameras may suffer from noise contamination, causing issues for subsequent image analysis, such as image recognition, object tracking, and classification of an object in the image. This paper develops an effective combinational denoising framework based on the proposed Adaptive and Overlapped Average Filtering (AOAF) and Mixed-pooling Attention Refinement Networks (MARNs). First, we apply AOAF to the noisy input image to obtain a preliminarily denoised result, where noisy pixels are removed and recovered. Next, MARNs take the preliminary result as the input and output a refined image where details and edges are better reconstructed. The experimental results demonstrate that our method performs favorably against state-of-the-art denoising methods. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
40. In silico pace-mapping: prediction of left vs. right outflow tract origin in idiopathic ventricular arrhythmias with patient-specific electrophysiological simulations.
- Author
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Doste R, Sebastian R, Gomez JF, Soto-Iglesias D, Alcaine A, Mont L, Berruezo A, Penela D, and Camara O
- Subjects
- Arrhythmias, Cardiac diagnosis, Computer Simulation, Electrocardiography, Heart Ventricles diagnostic imaging, Heart Ventricles surgery, Humans, Catheter Ablation, Tachycardia, Ventricular diagnosis, Tachycardia, Ventricular surgery
- Abstract
Aims: A pre-operative non-invasive identification of the site of origin (SOO) of outflow tract ventricular arrhythmias (OTVAs) is important to properly plan radiofrequency ablation procedures. Although some algorithms based on electrocardiograms (ECGs) have been developed to predict left vs. right ventricular origins, their accuracy is still limited, especially in complex anatomies. The aim of this work is to use patient-specific electrophysiological simulations of the heart to predict the SOO in OTVA patients., Methods and Results: An in silico pace-mapping procedure was designed and used on 11 heart geometries, generating for each case simulated ECGs from 12 clinically plausible SOO. Subsequently, the simulated ECGs were compared with patient ECG data obtained during the clinical tachycardia using the 12-lead correlation coefficient (12-lead ρ). Left ventricle (LV) vs. right ventricle (RV) SOO was estimated by computing the LV/RV ratio for each patient, obtained by dividing the average 12-lead ρ value of the LV- and RV-SOO simulated ECGs, respectively. Simulated ECGs that had virtual sites close to the ablation points that stopped the arrhythmia presented higher correlation coefficients. The LV/RV ratio correctly predicted LV vs. RV SOO in 10/11 cases; 1.07 vs. 0.93 P < 0.05 for 12-lead ρ., Conclusion: The obtained results demonstrate the potential of the developed in silico pace-mapping technique to complement standard ECG for the pre-operative planning of complex ventricular arrhythmias., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author(s) 2020. For permissions, please email: journals.permissions@oup.com.)
- Published
- 2020
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- View/download PDF
41. Gender differences in sleep patterns and sleep complaints of elite athletes.
- Author
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Silva A, Narciso FV, Rosa JP, Rodrigues DF, Cruz AÂDS, Tufik S, Viana F, Bichara JJ, Pereira SRD, da Silva SC, and Mello MT
- Abstract
Objective: The present study aimed to investigate the gender differences for sleep complaints, patterns and disorders of elite athletes during preparation for the Rio 2016 Olympic Games., Methods: The study included 146 athletes from the Brazilian Olympic Team (male: n=86; 59%; female: n=60; 41%). The assessment of the Olympic athletes' sleep took place in 2015, during the preparation period for the Rio Olympic Games. The athletes underwent a single polysomnography (PSG) evaluation. Sleep specialists evaluated the athletes and asked about their sleep complaints during a clinical consultation. In this evaluation week, the athletes did not take part in any training or competitions., Results: The prevalence of sleep complaints was 53% of the athletes during the medical consultation, the most prevalent being insufficient sleep/waking up tired (32%), followed by snoring (21%) and insomnia (19.2%). In relation to the sleep pattern findings, the men had significantly higher sleep latency and wake after sleep onset than the women ( p =0.004 and p =0.002, respectively). The sleep efficiency and sleep stages revealed that men had a lower percentage of sleep efficiency and slow wave sleep than the women ( p =0.001 and p =0.05, respectively)., Conclusion: Most athletes reported some sleep complaints, with men reporting more sleep complaints than women in the clinical evaluation. The PSG showed that 36% of all athletes had a sleep disorder with a greater reduction in sleep quality in men than in women.
- Published
- 2019
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42. Personalized Cardiac Computational Models: From Clinical Data to Simulation of Infarct-Related Ventricular Tachycardia.
- Author
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Lopez-Perez A, Sebastian R, Izquierdo M, Ruiz R, Bishop M, and Ferrero JM
- Abstract
In the chronic stage of myocardial infarction, a significant number of patients develop life-threatening ventricular tachycardias (VT) due to the arrhythmogenic nature of the remodeled myocardium. Radiofrequency ablation (RFA) is a common procedure to isolate reentry pathways across the infarct scar that are responsible for VT. Unfortunately, this strategy show relatively low success rates; up to 50% of patients experience recurrent VT after the procedure. In the last decade, intensive research in the field of computational cardiac electrophysiology (EP) has demonstrated the ability of three-dimensional (3D) cardiac computational models to perform in-silico EP studies. However, the personalization and modeling of certain key components remain challenging, particularly in the case of the infarct border zone (BZ). In this study, we used a clinical dataset from a patient with a history of infarct-related VT to build an image-based 3D ventricular model aimed at computational simulation of cardiac EP, including detailed patient-specific cardiac anatomy and infarct scar geometry. We modeled the BZ in eight different ways by combining the presence or absence of electrical remodeling with four different levels of image-based patchy fibrosis (0, 10, 20, and 30%). A 3D torso model was also constructed to compute the ECG. Patient-specific sinus activation patterns were simulated and validated against the patient's ECG. Subsequently, the pacing protocol used to induce reentrant VTs in the EP laboratory was reproduced in-silico . The clinical VT was induced with different versions of the model and from different pacing points, thus identifying the slow conducting channel responsible for such VT. Finally, the real patient's ECG recorded during VT episodes was used to validate our simulation results and to assess different strategies to model the BZ. Our study showed that reduced conduction velocities and heterogeneity in action potential duration in the BZ are the main factors in promoting reentrant activity. Either electrical remodeling or fibrosis in a degree of at least 30% in the BZ were required to initiate VT. Moreover, this proof-of-concept study confirms the feasibility of developing 3D computational models for cardiac EP able to reproduce cardiac activation in sinus rhythm and during VT, using exclusively non-invasive clinical data.
- Published
- 2019
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43. Overlapping events with application to image sequences.
- Author
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Ayala G, Sebastian R, Díaz ME, Díaz E, Zoncu R, and Toomre D
- Subjects
- Algorithms, Artificial Intelligence, Image Enhancement methods, Image Interpretation, Computer-Assisted methods, Information Storage and Retrieval methods, Pattern Recognition, Automated methods, Photography methods, Subtraction Technique, Video Recording methods
- Abstract
Counting spatially and temporally overlapping events in image sequences and estimating their shape-size and duration features are important issues in some applications. We propose a stochastic model, a particular case of the nonisotropic 3D Boolean model, for performing this analysis: the temporal Boolean model. Some probabilistic properties are derived and a methodology for parameter estimation from time-lapse image sequences is proposed using an explicit treatment of the temporal dimension. We estimate the mean number of germs per unit area and time, the mean grain size and the duration distribution. A wide simulation study in order to assess the proposed estimators showed promising results. The model was applied on biological image sequences of in-vivo cells in order to estimate new parameters such as the mean number and duration distribution of endocytic events. Our results show that the proposed temporal Boolean model is effective for obtaining information about dynamic processes which exhibit short-lived, but spatially and temporally overlapping events.
- Published
- 2006
- Full Text
- View/download PDF
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