| Records |
| Author |
Debora Gil; Jose Maria-Carazo; Roberto Marabini |
| Title |
On the nature of 2D crystal unbending |
Type |
Journal Article |
| Year |
2006 |
Publication |
Journal of Structural Biology |
Abbreviated Journal |
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| Volume |
156 |
Issue |
3 |
Pages |
546-555 |
| Keywords |
Electron microscopy |
| Abstract |
Crystal unbending, the process that aims to recover a perfect crystal from experimental data, is one of the more important steps in electron crystallography image processing. The unbending process involves three steps: estimation of the unit cell displacements from their ideal positions, extension of the deformation field to the whole image and transformation of the image in order to recover an ideal crystal. In this work, we present a systematic analysis of the second step oriented to address two issues. First, whether the unit cells remain undistorted and only the distance between them should be changed (rigid case) or should be modified with the same deformation suffered by the whole crystal (elastic case). Second, the performance of different extension algorithms (interpolation versus approximation) is explored. Our experiments show that there is no difference between elastic and rigid cases or among the extension algorithms. This implies that the deformation fields are constant over large areas. Furthermore, our results indicate that the main source of error is the transformation of the crystal image. |
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| ISSN |
1047-8477 |
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IAM; |
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no |
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IAM @ iam @ GCM2006 |
Serial |
1519 |
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| Author |
Debora Gil; Jaume Garcia; Manuel Vazquez; Ruth Aris; Guillaume Houzeaux |
| Title |
Patient-Sensitive Anatomic and Functional 3D Model of the Left Ventricle Function |
Type |
Conference Article |
| Year |
2008 |
Publication |
8th World Congress on Computational Mechanichs (WCCM8)/5th European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS 2008) |
Abbreviated Journal |
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Issue |
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Pages |
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| Keywords |
Left Ventricle; Electromechanical Models; Image Processing; Magnetic Resonance. |
| Abstract |
Early diagnosis and accurate treatment of Left Ventricle (LV) dysfunction significantly increases the patient survival. Impairment of LV contractility due to cardiovascular diseases is reflected in its motion patterns. Recent advances in medical imaging, such as Magnetic Resonance (MR), have encouraged research on 3D simulation and modelling of the LV dynamics. Most of the existing 3D models consider just the gross anatomy of the LV and restore a truncated ellipse which deforms along the cardiac cycle. The contraction mechanics of any muscle strongly depends on the spatial orientation of its muscular fibers since the motion that the muscle undergoes mainly takes place along the fibers. It follows that such simplified models do not allow evaluation of the heart electro-mechanical function and coupling, which has recently risen as the key point for understanding the LV functionality . In order to thoroughly understand the LV mechanics it is necessary to consider the complete anatomy of the LV given by the orientation of the myocardial fibres in 3D space as described by Torrent Guasp. We propose developing a 3D patient-sensitive model of the LV integrating, for the first time, the ven- tricular band anatomy (fibers orientation), the LV gross anatomy and its functionality. Such model will represent the LV function as a natural consequence of its own ventricular band anatomy. This might be decisive in restoring a proper LV contraction in patients undergoing pace marker treatment. The LV function is defined as soon as the propagation of the contractile electromechanical pulse has been modelled. In our experiments we have used the wave equation for the propagation of the electric pulse. The electromechanical wave moves on the myocardial surface and should have a conductivity tensor oriented along the muscular fibers. Thus, whatever mathematical model for electric pulse propa- gation [4] we consider, the complete anatomy of the LV should be extracted. The LV gross anatomy is obtained by processing multi slice MR images recorded for each patient. Information about the myocardial fibers distribution can only be extracted by Diffusion Tensor Imag- ing (DTI), which can not provide in vivo information for each patient. As a first approach, we have computed an average model of fibers from several DTI studies of canine hearts. This rough anatomy is the input for our electro-mechanical propagation model simulating LV dynamics. The average fiber orientation is updated until the simulated LV motion agrees with the experimental evidence provided by the LV motion observed in tagged MR (TMR) sequences. Experimental LV motion is recovered by applying image processing, differential geometry and interpolation techniques to 2D TMR slices [5]. The pipeline in figure 1 outlines the interaction between simulations and experimental data leading to our patient-tailored model. |
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Place of Publication |
Venezia (Italia) |
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B-31470-08 |
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IAM |
Approved |
no |
| Call Number |
IAM @ iam @ GGV2008c |
Serial |
1521 |
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| Author |
Debora Gil; Aura Hernandez-Sabate; Oriol Rodriguez; J. Mauri; Petia Radeva |
| Title |
Statistical Strategy for Anisotropic Adventitia Modelling in IVUS |
Type |
Journal Article |
| Year |
2006 |
Publication |
IEEE Transactions on Medical Imaging |
Abbreviated Journal |
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| Volume |
25 |
Issue |
6 |
Pages |
768-778 |
| Keywords |
Corners; T-junctions; Wavelets |
| Abstract |
Vessel plaque assessment by analysis of intravascular ultrasound sequences is a useful tool for cardiac disease diagnosis and intervention. Manual detection of luminal (inner) and mediaadventitia (external) vessel borders is the main activity of physicians in the process of lumen narrowing (plaque) quantification. Difficult definition of vessel border descriptors, as well as, shades, artifacts, and blurred signal response due to ultrasound physical properties trouble automated adventitia segmentation. In order to efficiently approach such a complex problem, we propose blending advanced anisotropic filtering operators and statistical classification techniques into a vessel border modelling strategy. Our systematic statistical analysis shows that the reported adventitia detection achieves an accuracy in the range of interobserver variability regardless of plaque nature, vessel geometry, and incomplete vessel borders. Index Terms–-Anisotropic processing, intravascular ultrasound (IVUS), vessel border segmentation, vessel structure classification. |
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IAM;MILAB |
Approved |
no |
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IAM @ iam @ GHR2006 |
Serial |
1525 |
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| Author |
Debora Gil; Aura Hernandez-Sabate; Mireia Brunat;Steven Jansen; Jordi Martinez-Vilalta |
| Title |
Structure-preserving smoothing of biomedical images |
Type |
Journal Article |
| Year |
2011 |
Publication |
Pattern Recognition |
Abbreviated Journal |
PR |
| Volume |
44 |
Issue |
9 |
Pages |
1842-1851 |
| Keywords |
Non-linear smoothing; Differential geometry; Anatomical structures; segmentation; Cardiac magnetic resonance; Computerized tomography |
| Abstract |
Smoothing of biomedical images should preserve gray-level transitions between adjacent tissues, while restoring contours consistent with anatomical structures. Anisotropic diffusion operators are based on image appearance discontinuities (either local or contextual) and might fail at weak inter-tissue transitions. Meanwhile, the output of block-wise and morphological operations is prone to present a block structure due to the shape and size of the considered pixel neighborhood. In this contribution, we use differential geometry concepts to define a diffusion operator that restricts to image consistent level-sets. In this manner, the final state is a non-uniform intensity image presenting homogeneous inter-tissue transitions along anatomical structures, while smoothing intra-structure texture. Experiments on different types of medical images (magnetic resonance, computerized tomography) illustrate its benefit on a further process (such as segmentation) of images. |
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Edition |
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0031-3203 |
ISBN |
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Conference |
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| Notes |
IAM; ADAS |
Approved |
no |
| Call Number |
IAM @ iam @ GHB2011 |
Serial |
1526 |
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| Author |
Debora Gil; Oriol Rodriguez; J. Mauri; Petia Radeva |
| Title |
Statistical descriptors of the Myocardial perfusion in angiographic images |
Type |
Conference Article |
| Year |
2006 |
Publication |
Proc. Computers in Cardiology |
Abbreviated Journal |
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| Volume |
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Issue |
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Pages |
677-680 |
| Keywords |
Anisotropic processing; intravascular ultrasound (IVUS); vessel border segmentation; vessel structure classification. |
| Abstract |
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;MILAB |
Approved |
no |
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IAM @ iam @ GRR2006 |
Serial |
1528 |
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| Author |
Debora Gil; Petia Radeva |
| Title |
Inhibition of false landmarks |
Type |
Journal Article |
| Year |
2006 |
Publication |
Pattern Recognition Letters |
Abbreviated Journal |
PRL |
| Volume |
27 |
Issue |
9 |
Pages |
1022-1030 |
| Keywords |
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| Abstract |
Corners and junctions are landmarks characterized by the lack of differentiability in the unit tangent to the image level curve. Detectors based on differential operators are not, by their own definition, the best posed as they require a higher degree of differentiability to yield a reliable response. We argue that a corner detector should be based on the degree of continuity of the tangent vector to the image level sets, work on the image domain and need no assumptions on neither the image local structure nor the particular geometry of the corner/junction. An operator measuring the degree of differentiability of the projection matrix on the image gradient fulfills the above requirements. Because using smoothing kernels leads to corner misplacement, we suggest an alternative fake response remover based on the receptive field inhibition of spurious details. The combination of both orientation discontinuity detection and noise inhibition produce our inhibition orientation energy (IOE) landmark locator. |
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Elsevier Science Inc. |
Place of Publication |
New York, NY, USA |
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Series Issue |
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Edition |
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| ISSN |
0167-8655 |
ISBN |
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Conference |
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| Notes |
IAM;MILAB |
Approved |
no |
| Call Number |
IAM @ iam @ GiR2006 |
Serial |
1529 |
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| Author |
Debora Gil; Petia Radeva |
| Title |
Extending anisotropic operators to recover smooth shapes |
Type |
Journal Article |
| Year |
2005 |
Publication |
Computer Vision and Image Understanding |
Abbreviated Journal |
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| Volume |
99 |
Issue |
1 |
Pages |
110-125 |
| Keywords |
Contour completion; Functional extension; Differential operators; Riemmanian manifolds; Snake segmentation |
| Abstract |
Anisotropic differential operators are widely used in image enhancement processes. Recently, their property of smoothly extending functions to the whole image domain has begun to be exploited. Strong ellipticity of differential operators is a requirement that ensures existence of a unique solution. This condition is too restrictive for operators designed to extend image level sets: their own functionality implies that they should restrict to some vector field. The diffusion tensor that defines the diffusion operator links anisotropic processes with Riemmanian manifolds. In this context, degeneracy implies restricting diffusion to the varieties generated by the vector fields of positive eigenvalues, provided that an integrability condition is satisfied. We will use that any smooth vector field fulfills this integrability requirement to design line connection algorithms for contour completion. As application we present a segmenting strategy that assures convergent snakes whatever the geometry of the object to be modelled is. |
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Edition |
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| ISSN |
1077-3142 |
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| Notes |
IAM;MILAB |
Approved |
no |
| Call Number |
IAM @ iam @ GIR2005 |
Serial |
1530 |
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| Author |
Debora Gil; Petia Radeva |
| Title |
Shape Restoration via a Regularized Curvature Flow |
Type |
Journal Article |
| Year |
2004 |
Publication |
Journal of Mathematical Imaging and Vision |
Abbreviated Journal |
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| Volume |
21 |
Issue |
3 |
Pages |
205-223 |
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| Abstract |
Any image filtering operator designed for automatic shape restoration should satisfy robustness (whatever the nature and degree of noise is) as well as non-trivial smooth asymptotic behavior. Moreover, a stopping criterion should be determined by characteristics of the evolved image rather than dependent on the number of iterations. Among the several PDE based techniques, curvature flows appear to be highly reliable for strongly noisy images compared to image diffusion processes.
In the present paper, we introduce a regularized curvature flow (RCF) that admits non-trivial steady states. It is based on a measure of the local curve smoothness that takes into account regularity of the curve curvature and serves as stopping term in the mean curvature flow. We prove that this measure decreases over the orbits of RCF, which endows the method with a natural stop criterion in terms of the magnitude of this measure. Further, in its discrete version it produces steady states consisting of piece-wise regular curves. Numerical experiments made on synthetic shapes corrupted with different kinds of noise show the abilities and limitations of each of the current geometric flows and the benefits of RCF. Finally, we present results on real images that illustrate the usefulness of the present approach in practical applications. |
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IAM;MILAB |
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no |
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IAM @ iam @ GiR2004c |
Serial |
1532 |
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| Author |
Debora Gil; Petia Radeva |
| Title |
Inhibition of False Landmarks |
Type |
Book Chapter |
| Year |
2004 |
Publication |
Recent Advances in Artificial Intelligence Research and Development |
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Issue |
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Pages |
233-244 |
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| Abstract |
We argue that a corner detector should be based on the degree of continuity of the tangent vector to the image level sets, work on the image domain and need no assumptions on neither the image local structure nor the particular geometry of the corner/junction. An operator measuring the degree of differentiability of the projection matrix on the image gradient fulfills the above requirements. Its high sensitivity to changes in vector directions makes it suitable for landmark location in real images prone to need smoothing to reduce the impact of noise. Because using smoothing kernels leads to corner misplacement, we suggest an alternative fake response remover based on the receptive field inhibition of spurious details. The combination of both orientation discontinuity detection and noise inhibition produce our Inhibition Orientation Energy (IOE) landmark locator. |
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| Publisher |
IOS Press |
Place of Publication |
Barcelona (Spain) |
Editor |
al, J.V. et |
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| Notes |
IAM;MILAB |
Approved |
no |
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IAM @ iam @ GiR2004a |
Serial |
1533 |
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| Author |
Debora Gil; Petia Radeva |
| Title |
Curvature based Distance Maps |
Type |
Report |
| Year |
2003 |
Publication |
CVC Technical Report |
Abbreviated Journal |
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Issue |
70 |
Pages |
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Computer Vision Center |
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IAM;MILAB |
Approved |
no |
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IAM @ iam @ GIR2003a |
Serial |
1534 |
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| Author |
Debora Gil; Petia Radeva |
| Title |
Curvature Vector Flow to Assure Convergent Deformable Models for Shape Modelling |
Type |
Book Chapter |
| Year |
2003 |
Publication |
Energy Minimization Methods In Computer Vision And Pattern Recognition |
Abbreviated Journal |
LNCS |
| Volume |
2683 |
Issue |
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Pages |
357-372 |
| Keywords |
Initial condition; Convex shape; Non convex analysis; Increase; Segmentation; Gradient; Standard; Standards; Concave shape; Flow models; Tracking; Edge detection; Curvature |
| Abstract |
Poor convergence to concave shapes is a main limitation of snakes as a standard segmentation and shape modelling technique. The gradient of the external energy of the snake represents a force that pushes the snake into concave regions, as its internal energy increases when new inexion points are created. In spite of the improvement of the external energy by the gradient vector ow technique, highly non convex shapes can not be obtained, yet. In the present paper, we develop a new external energy based on the geometry of the curve to be modelled. By tracking back the deformation of a curve that evolves by minimum curvature ow, we construct a distance map that encapsulates the natural way of adapting to non convex shapes. The gradient of this map, which we call curvature vector ow (CVF), is capable of attracting a snake towards any contour, whatever its geometry. Our experiments show that, any initial snake condition converges to the curve to be modelled in optimal time. |
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Springer, Berlin |
Place of Publication |
Lisbon, PORTUGAL |
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Springer, B. |
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Lecture Notes in Computer Science |
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LNCS |
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0302-9743 |
ISBN |
3-540-40498-8 |
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IAM;MILAB |
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no |
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IAM @ iam @ GIR2003b |
Serial |
1535 |
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| Author |
Debora Gil; Petia Radeva; J. Mauri |
| Title |
Ivus Segmentation Via a Regularized Curvature Flow |
Type |
Conference Article |
| Year |
2002 |
Publication |
X Congreso Anual de la Sociedad Española de Ingeniería Biomédica CASEIB 2002 |
Abbreviated Journal |
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Pages |
133-136 |
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| Abstract |
Cardiac diseases are diagnosed and treated through a study of the morphology and dynamics of cardiac arteries. In- travascular Ultrasound (IVUS) imaging is of high interest to physicians since it provides both information. At the current state-of-the-art in image segmentation, a robust detection of the arterial lumen in IVUS demands manual intervention or ECG-gating. Manual intervention is a tedious and time consuming task that requires experienced observers, meanwhile ECG-gating is an acquisition technique not available in all clinical centers. We introduce a parametric algorithm that detects the arterial luminal border in in vivo sequences. The method consist in smoothing the sequences’ level surfaces under a regularized mean curvature flow that admits non-trivial steady states. The flow is based on a measure of the surface local smoothness that takes into account regularity of the surface curvature. |
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Saragossa, Espanya |
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IAM;MILAB |
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no |
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IAM @ iam @ GRM2002 |
Serial |
1536 |
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| Author |
Debora Gil; Petia Radeva; Jordi Saludes; J. Mauri |
| Title |
Automatic Segmentation of Artery Wall in Coronary IVUS Images: A Probabilistic Approach |
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Conference Article |
| Year |
2000 |
Publication |
International Conference on Pattern Recognition |
Abbreviated Journal |
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4 |
Issue |
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Pages |
352-355 |
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Intravascular ultrasound images represent a unique tool to analyze the morphology of arteries and vessels (plaques, restenosis, etc). The poor quality of these images makes unsupervised segmentation based on traditional segmentation algorithms (such as edge or ridge/valley detection) fail to achieve the expected results. In this paper we present a probabilistic flexible template to separate different regions in the image. In particular, we use elliptic templates to model and detect the shape of the vessel inner wall in IVUS images. We present the results of successful segmentation obtained from patients undergoing stent treatment. A physician team has validated these results. |
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IAM;MILAB |
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no |
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IAM @ iam @ GRS2000a |
Serial |
1537 |
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| Author |
Debora Gil; Petia Radeva; Fernando Vilariño |
| Title |
Anisotropic Contour Completion |
Type |
Conference Article |
| Year |
2003 |
Publication |
Proceedings of the IEEE International Conference on Image Processing |
Abbreviated Journal |
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Issue |
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In this paper we introduce a novel application of the diffusion tensor for anisotropic image processing. The Anisotropic Contour Completion (ACC) we suggest consists in extending the characteristic function of the open curve by means of a degenerated diffusion tensor that prevents any diffusion in the normal direction. We show that ACC is equivalent to a dilation with a continuous elliptic structural element that takes into account the local orientation of the contours to be closed. Experiments on contours extracted from real images show that ACC produces shapes able to adapt to any curve in an active contour framework. 1. |
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Barcelona, Spain |
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0-7803-7751-6 |
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IAM;MV;MILAB;SIAI |
Approved |
no |
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IAM @ iam @ GRV2003 |
Serial |
1539 |
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| Author |
Debora Gil; Oriol Rodriguez-Leor; Petia Radeva; Aura Hernandez-Sabate |
| Title |
Assessing Artery Motion Compensation in IVUS |
Type |
Book Chapter |
| Year |
2007 |
Publication |
Computer Analysis Of Images And Patterns |
Abbreviated Journal |
LNCS |
| Volume |
4673 |
Issue |
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Pages |
213-220 |
| Keywords |
validation standards; quality measures; IVUS motion compensation; conservation laws; Fourier development |
| Abstract |
Cardiac dynamics suppression is a main issue for visual improvement and computation of tissue mechanical properties in IntraVascular UltraSound (IVUS). Although in recent times several motion compensation techniques have arisen, there is a lack of objective evaluation of motion reduction in in vivo pullbacks. We consider that the assessment protocol deserves special attention for the sake of a clinical applicability as reliable as possible. Our work focuses on defining a quality measure and a validation protocol assessing IVUS motion compensation. On the grounds of continuum mechanics laws we introduce a novel score measuring motion reduction in in vivo sequences. 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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Springerlink |
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Heidelberg |
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Lecture Notes in Computer Science |
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978-3-540-74271-5 |
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IAM;MILAB |
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IAM @ iam @ GRR2007 |
Serial |
1540 |
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