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Aura Hernandez-Sabate; Debora Gil; Albert Teis |
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Title |
How Do Conservation Laws Define a Motion Suppression Score in In-Vivo Ivus Sequences? |
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2007 |
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Proc. IEEE Ultrasonics Symp |
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2231-2234 |
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validation standards; IVUS motion compensation; conservation laws. |
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Evaluation of arterial tissue biomechanics for diagnosis and treatment of cardiovascular diseases is an active research field in the biomedical imaging processing area. IntraVascular UltraSound (IVUS) is a unique tool for such assessment since it reflects tissue morphology and deformation. A proper quantification and visualization of both properties is hindered by vessel structures misalignments introduced by cardiac dynamics. This has encouraged development of IVUS motion compensation techniques. However, there is a lack of an objective evaluation of motion reduction ensuring a reliable clinical application This work reports a novel score, the Conservation of Density Rate (CDR), for validation of motion compensation in in-vivo pullbacks. Synthetic experiments validate the proposed score as measure of motion parameters accuracy; while results in in vivo pullbacks show its reliability in clinical cases. |
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IAM @ iam @ HTG2007 |
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1550 |
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Enric Marti; Carme Julia; Debora Gil |
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Title |
A PBL Experience in the Teaching of Computer Graphics |
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Conference Article |
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2007 |
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XVII Congreso Español de Informàtica Gráfica |
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25 |
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1 |
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95-103 |
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Project-Based Learning (PBL) is an educational strategy to improve student’s learning capability that, in recent years, has had a progressive acceptance in undergraduate studies. This methodology is based on solving a problem or project in a student working group. In this way, PBL focuses on learning the necessary tools to correctly find a solution to given problems. Since the learning initiative is transferred to the student, the PBL method promotes students own abilities. This allows a better assessment of the true workload that carries out the student in the subject. It follows that the methodology conforms to the guidelines of the Bologna document, which quantifies the student workload in a subject by means of the European credit transfer system (ECTS). PBL is currently applied in undergraduate studies needing strong practical training such as medicine, nursing or law sciences. Although this is also the case in engineering studies, amazingly, few experiences have been reported. In this paper we propose to use PBL in the educational organization of the Computer Graphics subjects in the Computer Science degree. Our PBL project focuses in the development of a C++ graphical environment based on the OpenGL libraries for visualization and handling of different graphical objects. The starting point is a basic skeleton that already includes lighting functions, perspective projection with mouse interaction to change the point of view and three predefined objects. Students have to complete this skeleton by adding their own functions to solve the project. A total number of 10 projects have been proposed and successfully solved. The exercises range from human face rendering to articulated objects, such as robot arms or puppets. In the present paper we extensively report the statement and educational objectives for two of the projects: solar system visualization and a chess game. We report our earlier educational experience based on the standard classroom theoretical, problem and practice sessions and the reasons that motivated searching for other learning methods. We have mainly chosen PBL because it improves the student learning initiative. We have applied the PBL educational model since the beginning of the second semester. The student’s feedback increases in his interest for the subject. We present a comparative study of the teachers’ and students’ workload between PBL and the classic teaching approach, which suggests that the workload increase in PBL is not as high as it seems. |
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Zaragoza; September 2007 |
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CEDI |
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IAM;ADAS; |
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IAM @ iam @ MJG2007a |
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1603 |
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Oriol Rodriguez-Leon; Debora Gil; Eduard Fernandez-Nofrerias; H.Tizon; S.Montserrat; Vicente del Valle;Josefina Mauri |
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Caracterització de la Perfusió Miocàrdica mitjançant anàlisi estadístic de l espectre en l angiografia de contrast |
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2007 |
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XIX Congrés de la Societat Catalana de Cardiologia de Barcelona |
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130 |
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La valoració de la integritat de la microcirculació coronària aporta informació pronòstica en pacients amb infart agut de miocardi en els que es realitza angioplastia primària. Aquesta valoració és subjectiva i presenta una important variabilitat si no es duta a terme per personal experimentat. Presentem una eina d’anàlisi d’imatge que permet fer una valoració de la microcirculació coronària a partir de seqüències d’angiografia. Hem analitzat les variacions locals en el nivell de gris de la imatge durant la seqüència angiogràfica. Hem identificat els principals fenòmens observats (respiració, batec cardíac, tinció arterial, tinció miocàrdica i soroll radiològic) mitjançant un anàlisi estadístic de l’espectre de Fourier de l’evolució al llarg del temps de la mitja local. Aquest mateix anàlisis permet determinat la influència de cadascun d’ells en la extracció del patró de tinció i selecciona la respiració com el fenomen que més distorsiona el patró de tinció original. Els descriptors proposats s’obtenen fora del rang espectral respiratori. Hem testat la seva capacitat per a detectar els tres fenòmens principals (tinció miocàrdica (MS), tinció arterial (AS) i soroll (NS)) independentment de la respiració. La capacitat de discriminació dels descriptors ha estat valorada mitjançant un mètode de crossvalidation en 30 seqüències d’angiografia. Els descriptors emprats permeten caracteritzar la tinció miocàrdica amb una alta eficiència i fiabilitat. A més no hi ha diferències significatives en l’anàlisi de les seqüències obtingudes amb el pacient respirant amb normalitat o en apnea |
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Barcelona (Spain) |
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IAM @ iam @ RGF2007 |
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1639 |
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Joel Barajas; Jaume Garcia; Karla Lizbeth Caballero; Francesc Carreras; Sandra Pujades; Petia Radeva |
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Title |
Correction of Misalignment Artifacts Among 2-D Cardiac MR Images in 3-D Space |
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Conference Article |
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2006 |
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1st International Wokshop on Computer Vision for Intravascular and Intracardiac Imaging (CVII’06) |
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3217 |
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114-121 |
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Cardiac Magnetic Resonance images offer the opportunity to study the heart in detail. One of the main issues in its modelling is to create an accurate 3-D reconstruction of the left ventricle from 2-D views. A first step to achieve this goal is the correct registration among the different image planes due to patient movements. In this article, we present an accurate method to correct displacement artifacts using the Normalized Mutual Information. Here, the image views are treated as planes in order to diminish the approximation error caused by the association of a certain thickness, and moved simultaneously to avoid any kind of bias in the alignment process. This method has been validated using real and syntectic plane displacements, yielding promising results. |
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Copenhagen (Denmark) |
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978-3-540-22977-3 |
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IAM;MILAB |
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IAM @ iam @ BGC2006 |
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1485 |
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Author |
Paula Fritzsche; C.Roig; Ana Ripoll; Emilio Luque; Aura Hernandez-Sabate |
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A Performance Prediction Methodology for Data-dependent Parallel Applications |
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2006 |
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Proceedings of the IEEE International Conference on Cluster Computing |
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1-8 |
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The increase in the use of parallel distributed architectures in order to solve large-scale scientific problems has generated the need for performance prediction for both deterministic applications and non-deterministic applications. In particular, the performance prediction of data dependent programs is an extremely challenging problem because for a specific issue the input datasets may cause different execution times. Generally, a parallel application is characterized as a collection of tasks and their interrelations. If the application is time-critical it is not enough to work with only one value per task, and consequently knowledge of the distribution of task execution times is crucial. The development of a new prediction methodology to estimate the performance of data-dependent parallel applications is the primary target of this study. This approach makes it possible to evaluate the parallel performance of an application without the need of implementation. A real data-dependent arterial structure detection application model is used to apply the methodology proposed. The predicted times obtained using the new methodology for genuine datasets are compared with predicted times that arise from using only one execution value per task. Finally, the experimental study shows that the new methodology generates more precise predictions. |
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IAM @ iam @ FRR2006 |
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1497 |
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Jaume Garcia; Debora Gil; Joel Barajas; Francesc Carreras; Sandra Pujades; Petia Radeva |
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Characterization of ventricular torsion in healthy subjects using Gabor filters and a variational framework |
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2006 |
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Proc. Computers in Cardiology |
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877-880 |
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In this work, we present a fully automated method for tissue deformation estimation in tagged magnetic resonance images (TMRI). Gabor filter banks, tuned independently for each left ventricle level, provide optimally filtered complex images which phase remains constant along the cardiac cycle. This fact can be thought as the brightness constancy condition required by classical optical flow (OF) methods. Pairs of these filtered sequences, together with a variational formulation are used in a second step to obtain dense continuous deformation maps that we call Harmonic Phase Flow. This method has been used to determine reference values of ventricular torsion (VT) in a set of 8 healthy volunteers. The results encourage the use of VT as a useful parameter for ventricular function assessment in clinical routine. |
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IAM;MILAB |
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IAM @ iam @ GGB2006a |
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1509 |
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Debora Gil; Oriol Rodriguez; Josepa Mauri; Petia Radeva |
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Statistical descriptors of the Myocardial perfusion in angiographic images |
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2006 |
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Proc. Computers in Cardiology |
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677-680 |
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Anisotropic processing; intravascular ultrasound (IVUS); vessel border segmentation; vessel structure classification. |
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Restoration of coronary flow after primary percutaneous coronary intervention in acute myocardial infarction does not always correlate with adequate myocardial perfusion. Recently, coronary angiography has been used to assess microcirculation integrity (Myocardial BlushAnalysis, MBA). Although MBA correlates with patient prognosis there are few image processing methods addressing objective perfusion quantification. The goal of this work is to develop statistical descriptors of the myocardial dyeing pattern allowing objective assessment of myocardial perfusion. Experiments on healthy right coronary arteries show that our approach allows reliable measurements without any specific image acquisition protocol. |
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IAM @ iam @ GRR2006 |
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1528 |
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Aura Hernandez-Sabate; Petia Radeva; Antonio Tovar; Debora Gil |
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Vessel structures alignment by spectral analysis of ivus sequences |
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2006 |
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Proc. of CVII, MICCAI Workshop |
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39-36 |
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Three-dimensional intravascular ultrasound (IVUS) allows to visualize and obtain volumetric measurements of coronary lesions through an exploration of the cross sections and longitudinal views of arteries. However, the visualization and subsequent morpho-geometric measurements in IVUS longitudinal cuts are subject to distortion caused by periodic image/vessel motion around the IVUS catheter. Usually, to overcome the image motion artifact ECG-gating and image-gated approaches are proposed, leading to slowing the pullback acquisition or disregarding part of IVUS data. In this paper, we argue that the image motion is due to 3-D vessel geometry as well as cardiac dynamics, and propose a dynamic model based on the tracking of an elliptical vessel approximation to recover the rigid transformation and align IVUS images without loosing any IVUS data. We report an extensive validation with synthetic simulated data and in vivo IVUS sequences of 30 patients achieving an average reduction of the image artifact of 97% in synthetic data and 79% in real-data. Our study shows that IVUS alignment improves longitudinal analysis of the IVUS data and is a necessary step towards accurate reconstruction and volumetric measurements of 3-D IVUS. |
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Copenhaguen (Denmark), |
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1st International Wokshop on Computer Vision for Intravascular and Intracardiac Imaging (CVII’06) |
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IAM; MILAB |
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IAM @ iam @ HRT2006 |
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1552 |
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Aura Hernandez-Sabate; Debora Gil; Josefina Mauri; Petia Radeva |
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Reducing cardiac motion in IVUS sequences |
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2006 |
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Proceeding of Computers in Cardiology |
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33 |
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685-688 |
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Cardiac vessel displacement is a main artifact in IVUS sequences. It hinders visualization of the main structures in an appropriate orientation and alignment and affects extracting vessel measurements. In this paper, we present a novel approach for image sequence alignment based on spectral analysis, which removes rigid dynamics, preserving at the same time the vessel geometry. First, we suppress the translation by taking, for each frame, the center of mass of the image as origin of coordinates. In polar coordinates with such point as origin, the rotation appears as a horizontal displacement. The translation induces a phase shift in the Fourier coefficients of two consecutive polar images. We estimate the phase by adjusting a regression plane to the phases of the principal frequencies. Experiments show that the presented strategy suppress cardiac motion regardless of the acquisition device. 1. |
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IAM @ iam @ HGM2006a |
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1554 |
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Oriol Rodriguez-Leon; Eduard Fernandez-Nofrerias; Josefina Mauri; Vicente del Valle; Debora Gil; A.Barrios; E.Garcia; Petia Radeva |
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Perfusion ratio: A new tool to objectively assess microcirculation perfusion after primary Percutaneous Coronary Intervention |
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2006 |
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World Congress of Cardiology |
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859 |
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Barcelona (Spain) |
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IAM @ iam @ RFM2006c |
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1643 |
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