National Institute of Science and Technology in Medicine Assisted by Scientific Computing

and Technology in, Brazil

National Institute of Science and Technology in Medicine Assisted by Scientific Computing

and Technology in, Brazil
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Ares G.D.,National Laboratory for Scientific Computing | Ares G.D.,National Institute of Science and Technology in Medicine Assisted by Scientific Computing | Blanco P.J.,National Laboratory for Scientific Computing | Blanco P.J.,National Institute of Science and Technology in Medicine Assisted by Scientific Computing | And 4 more authors.
Computer Methods in Applied Mechanics and Engineering | Year: 2017

In the past decades a considerable amount of literature has been published addressing the study of the mechanical behavior of arterial walls. Ex-vivo experimentation made possible the development of constitutive models and the characterization of material parameters contributing to the understanding of the mechanobiological response of vascular tissues. Moreover, the existence of residual stresses in configurations free of load was revealed, and its impact in the general stress state of the tissue was quantified. In recent years, data assimilation techniques have seen a rapid development in cardiovascular modeling field, primarily focusing on the estimation of material parameters for arterial wall segments using information provided by medical imaging as well as by in-vitro settings. However, concerning the estimation of residual stresses, this research field is in its early stages, and much work is still required for the full functional characterization of arterial tissues. In this context, a conceptual variational framework for the development of residual stress estimation tools is proposed. Particularly, a variational formulation for the characterization of residual deformations and the associated stresses in arterial walls, based on full displacement field measurements of the vessel, is presented. Considering as known data the material parameters characterizing the behavior of the tissue and a set of arterial wall configurations at equilibrium with well defined pressure loads, we propose a cost functional that measures the mechanical imbalance caused by the lack of knowledge of residual stresses. In this manner, the characterization of residual stresses becomes a problem of minimizing such cost functional. Three numerical examples are presented highlighting the potential of the proposed approach. Among these examples, the characterization of residual stresses in a cylindrical geometry representing a three-layered aorta artery is performed. © 2017 Elsevier B.V.


Boileau E.,University of Swansea | Nithiarasu P.,University of Swansea | Blanco P.J.,National Laboratory for Scientific Computing | Blanco P.J.,National Institute of Science and Technology in Medicine Assisted by Scientific Computing | And 8 more authors.
International Journal for Numerical Methods in Biomedical Engineering | Year: 2015

Hæmodynamical simulations using one-dimensional (1D) computational models exhibit many of the features of the systemic circulation under normal and diseased conditions. Recent interest in verifying 1Dnumerical schemes has led to the development of alternative experimental setups and the use of three-dimensionalnumerical models to acquire data not easily measured in vivo. In most studies to date, only one particular 1Dscheme is tested. In this paper, we present a systematic comparison of six commonly used numerical schemes for 1Dblood flow modelling: discontinuous Galerkin, locally conservative Galerkin, Galerkin least-squares finite element method, finite volume method, finite difference MacCormack method and a simplified trapezium rule method. Comparisons are made in a series of six benchmark test cases with an increasing degree of complexity. The accuracy of the numerical schemes is assessed by comparison with theoretical results, three-dimensionalnumerical data in compatible domains with distensible walls or experimental data in a network of silicone tubes. Results show a good agreement among all numerical schemes and their ability to capture the main features of pressure, flow and area waveforms in large arteries. All the information used in this study, including the input data for all benchmark cases, experimental data where available and numerical solutions for each scheme, is made publicly available online, providing a comprehensive reference data set to support the development of 1Dmodels and numerical schemes. © 2015 John Wiley & Sons, Ltd.


Blanco P.J.,National Laboratory for Scientific Computing | Blanco P.J.,National Institute of Science and Technology in Medicine Assisted by Scientific Computing | Watanabe S.M.,National Institute of Science and Technology in Medicine Assisted by Scientific Computing | Watanabe S.M.,Federal Rural University of Pernambuco | And 6 more authors.
IEEE Transactions on Biomedical Engineering | Year: 2014

Simulation platforms are increasingly becoming complementary tools for cutting-edge cardiovascular research. The interplay among structural properties of the arterial wall, morphometry, anatomy, wave propagation phenomena, and ultimately, cardiovascular diseases continues to be poorly understood. Accurate models are powerful tools to shed light on these open problems. We developed an anatomically detailed computational model of the arterial vasculature to conduct 1-D blood flow simulations to serve as simulation infrastructure to aid cardiovascular research. An average arterial vasculature of a man was outlined in 3-D space to serve as geometrical substrate for the mathematical model. The architecture of this model comprises almost every arterial vessel acknowledged in the medical/anatomical literature, with a resolution down to the luminal area of perforator arteries. Over 2000 arterial vessels compose the model. Anatomical, physiological, and mechanical considerations were employed for the set up of model parameters and to determine criteria for blood flow distribution. Computational fluid dynamics was used to simulate blood flow and wave propagation phenomena in such arterial network. A sensitivity analysis was developed to unveil the contributions of model parameters to the conformation of the pressure waveforms. In addition, parameters were modified to target model to a patient-specific scenario. On the light of the knowledge domain, we conclude that the present model features excellent descriptive and predictive capabilities in both patient-generic and patient-specific cases, presenting a new step toward integrating an unprecedented anatomical description, morphometric, and simulations data to help in understanding complex arterial blood flow phenomena and related cardiovascular diseases. © 2014 IEEE.


PubMed | National Institute of Science and Technology in Medicine Assisted by Scientific Computing and University of Sao Paulo
Type: | Journal: Journal of biomechanics | Year: 2016

The goal of this work is to compare coronary hemodynamics as predicted by computational blood flow models derived from two imaging modalities: coronary computed tomography angiography (CCTA) and intravascular ultrasound integrated with angiography (IVUS). Criteria to define boundary conditions are proposed to overcome the dissimilar anatomical definition delivered by both modalities. The strategy to define boundary conditions is novel in the present context, and naturally accounts for the flow redistribution induced by the resistance of coronary vessels. Hyperemic conditions are assumed to assess model predictions under stressed hemodynamic environments similar to those encountered in Fractional Flow Reserve (FFR) calculations. As results, it was found that CCTA models predict larger pressure drops, higher average blood velocity and smaller FFR. Concerning the flow rate at distal locations in the major vessels of interest, it was found that CCTA predicted smaller flow than IVUS, which is a consequence of a larger sensitivity of CCTA models to coronary steal phenomena. Comparisons to in-vivo measurements of FFR are shown.


Blanco P.J.,Laboratorio Nacional Of Computacao Cientifica | Blanco P.J.,National Institute of Science and Technology in Medicine Assisted by Scientific Computing | Ares G.D.,Laboratorio Nacional Of Computacao Cientifica | Ares G.D.,National Institute of Science and Technology in Medicine Assisted by Scientific Computing | And 4 more authors.
Biomechanics and Modeling in Mechanobiology | Year: 2015

In this work, we address the simulation of three-dimensional arterial blood flow and its effect on the stress state of arterial walls. The novel contribution is the unprecedented combination of several modeling techniques to account for (1) the fact that known configurations for the arterial wall are in a preloaded state, (2) the compliance of the vessel segments, (3) proper boundary data over the non-physical interfaces resulting from the isolation of an arterial district from the rest of the arterial tree, (4) the presence of surrounding tissues in which the vessel is embedded and (5) residual stress state due to pre-stretch. Firstly, we formulate both the forward mechanical problem when the reference (zero-load) configuration is assumed to be known and, the preload problem arising when the known domain is a configuration at equilibrium with a certain load state (typically due to internal pressure and tethering forces). Then, two additional complexities are faced: the fluid–structure interaction problem that follows when the compliant vessels are coupled with the blood flow, and the introduction of non-physical boundaries coming from the artificial isolation of the arterial district from the original vessel. This, in turn, posses the problem of coupling dimensionally heterogeneous models to incorporate the effect of upstream and downstream systemic impedances. Additionally, a viscoelastic support on the external surface of the vessel is also incorporated. Two examples are presented to quantify in a physiologically consistent scenario the differences in simulation results when either considering or not the preload state of arterial walls. These computational simulations shed light on the validity of simplifying hypotheses in most hemodynamic models. © 2015 Springer-Verlag Berlin Heidelberg


Kapps G.W.,Brazilian Military Institute of Engineering | Oliveira J.C.D.,National Institute of Science and Technology in Medicine Assisted by Scientific Computing
Proceedings - 2012 14th Symposium on Virtual and Augmented Reality, SVR 2012 | Year: 2012

The cardiopulmonary arrest is responsible for a large amount of deaths. It is imperative that the resuscitation procedure gets performed promptly and efficiently. Such procedure is known as CPR. If the CPR procedure is not applied correctly it may aggravate the patient condition, which easily leads to death. CPR training is, henceforth, extremely important in order to ensure a proper CPR procedure that always improves the patient condition. Nowadays, CPR training is performed in custom built manikins, which allows one to get used to the right pressure to be performed. The system also requires an experienced instructor, which monitors and observes the individual under training. Such instructor keeps track of the frequency of thorax compression performed, as well as the proper posture adopted. Such setup gets expensive and slow-growing, as there must be one instructor for each and every student, as it is not possible for a student to self-evaluate his/her performance. Aiming at improving this scenario we developed PraCIMA, a training system for CPR procedure which allows a student to get automatic and precise feedback. The system uses a Wii Fit Balance Board to keep track of frequency, pressure as well as the angle in which the user performs the pressure. The system them parses all the information and plots a graphical output that intuitively shows how the user is performing, allowing for on-the-fly posture correction and self-evaluation, allowing him/her to improve his skills. An instructor now can follow several students at once. This work introduces the PraCiMA system, it components, the way it works as well as its contribution to CPR training. © 2012 IEEE.


Blanco P.J.,National Laboratory for Scientific Computing | Blanco P.J.,National Institute of Science and Technology in Medicine Assisted by Scientific Computing | Watanabe S.M.,National Laboratory for Scientific Computing | Watanabe S.M.,National Institute of Science and Technology in Medicine Assisted by Scientific Computing | And 5 more authors.
Biomechanics and Modeling in Mechanobiology | Year: 2014

Development of blood flow distribution criteria is a mandatory step toward developing computational models and numerical simulations of the systemic circulation. In the present work, we (i) present a systematic approach based on anatomical and physiological considerations to distribute the blood flow in a 1D anatomically detailed model of the arterial network and (ii) develop a numerical procedure to calibrate resistive parameters in terminal models in order to effectively satisfy such flow distribution. For the first goal, we merge data collected from the specialized medical literature with anatomical concepts such as vascular territories to determine blood flow supply to specific (encephalon, kidneys, etc.) and distributed (muscles, skin, etc.) organs. Overall, 28 entities representing the main specific organs are accounted for in the detailed description of the arterial topology that we use as model substrate. In turn, 116 vascular territories are considered as the basic blocks that compose the distributed organs throughout the whole body. For the second goal, Windkessel models are used to represent the peripheral beds, and the values of the resistive parameters are computed applying a Newton method to a parameter identification problem to guarantee the supply of the correct flow fraction to each terminal location according to the given criteria. Finally, it is shown that, by means of the criteria developed, and for a rather standard set of model parameters, the model predicts physiologically realistic pressure and flow waveforms. © 2014, Springer-Verlag Berlin Heidelberg.


Teixeira I.M.,National Institute of Science and Technology in Medicine Assisted by Scientific Computing | Braga R.M.,Federal University of Juiz de fora | Gomes A.T.A.,National Institute of Science and Technology in Medicine Assisted by Scientific Computing
CIBSE 2014: Proceedings of the 17th Ibero-American Conference Software Engineering | Year: 2014

Model-Driven Development (MDD) techniques provide a better articulation between domain experts and developers, allowing reductions on software development cost. Clinical data models based on open standard specifications facilitate the application of MDD techniques in the domain of Health Information Systems (HIS). Nevertheless, the use of clinical data models alone does not solve the fundamental problem of high development cost for HIS, since further information (e.g. architectural information) is usually necessary in the model transformation processes that MDD techniques employ. In this context, we present a code generation system that combines clinical data models based on openEHR specifications and high-level architectural descriptions based on constructs usually offered by Architectural Description Languages (ADL). We apply this system to the automatic synthesis of graphical user interfaces (GUI) for HIS, and argue about the hypothesis that our proposal can better articulate domain experts and developers of HIS, while simplifying the specification of model transformations.


Kulberg M.,Brazilian Military Institute of Engineering | Oliveira J.C.D.,National Institute of Science and Technology in Medicine Assisted by Scientific Computing | Rosa P.F.F.,Brazilian Military Institute of Engineering
Proceedings - 2011 13th Symposium on Virtual Reality, SVR 2011 | Year: 2011

This works aims at describing the design and implementation of a portable 3D VR setup. We use off the shelf parts which lead to an overall low cost. Unlike some related work, our prototype is fully enclosed (and independent of extra external parts to work). In this manuscript we describe the prototype as well as exploit use cases scenarios. © 2011 IEEE.


PubMed | National Institute of Science and Technology in Medicine Assisted by Scientific Computing and Laboratorio Nacional Of Computacao Cientifica
Type: Journal Article | Journal: Biomechanics and modeling in mechanobiology | Year: 2016

In this work, we address the simulation of three-dimensional arterial blood flow and its effect on the stress state of arterial walls. The novel contribution is the unprecedented combination of several modeling techniques to account for (1) the fact that known configurations for the arterial wall are in a preloaded state, (2) the compliance of the vessel segments, (3) proper boundary data over the non-physical interfaces resulting from the isolation of an arterial district from the rest of the arterial tree, (4) the presence of surrounding tissues in which the vessel is embedded and (5) residual stress state due to pre-stretch. Firstly, we formulate both the forward mechanical problem when the reference (zero-load) configuration is assumed to be known and, the preload problem arising when the known domain is a configuration at equilibrium with a certain load state (typically due to internal pressure and tethering forces). Then, two additional complexities are faced: the fluid-structure interaction problem that follows when the compliant vessels are coupled with the blood flow, and the introduction of non-physical boundaries coming from the artificial isolation of the arterial district from the original vessel. This, in turn, posses the problem of coupling dimensionally heterogeneous models to incorporate the effect of upstream and downstream systemic impedances. Additionally, a viscoelastic support on the external surface of the vessel is also incorporated. Two examples are presented to quantify in a physiologically consistent scenario the differences in simulation results when either considering or not the preload state of arterial walls. These computational simulations shed light on the validity of simplifying hypotheses in most hemodynamic models.

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