Showing papers by "Francoise Preteux published in 2006"

RIMES evaluation campaign for handwritten mail processing

Abstract: The paper presents the French RIMES (Reconnaissance et Indexation de donnees Manuscrites et de fac similES / Recognition and Indexing of handwritten documents and faxes) project, which is an evaluation campaign dedicated to automatic systems of recognition and indexing of handwritten letters such as those sent by postal mail or fax by individuals to companies or administrations. This project is intended to all the key players of the handwritten recognition and document analysis fields by proposing them to participate to evaluation tests, a first test having taken already place. In this framework, a new database of more than 5600 real mails completely annotated have been created as well as secondary databases of isolated characters, handwritten words (300 000 snippets) and logos. Beyond the evaluation, the other contribution of the RIMES project is to make available all these databases to the community after the last test

Opposed effects of hypertonic saline on contusions and noncontused brain tissue in patients with severe traumatic brain injury.

Abstract: Objective: The aim of this study was to quantify the effect of hypertonic saline solution on contused and noncontused brain tissue in patients with traumatic brain injury. We hypothesize that hypertonic saline would increase the volume of brain contusion while decreasing the volume of noncontused hemispheric areas. Design: Prospective observational study. Setting: Neurosciences critical care unit of a university hospital. Patients: Fourteen traumatic brain injury patients with increased intracranial pressure. Interventions: A computed tomography scan was performed before and after a 20-min infusion of 40 mL of 20% saline. Measurements and Main Results: The volume, weight, and specific gravity of contused and noncontused hemispheric areas were assessed from computed tomography DICOM images by using a custom-designed software (BrainView). Physiologic variables and natremia were measured before and after infusion. Hypertonic saline significantly increased natremia from 143 5 to 146 5 mmol/L and decreased intracranial pressure from 23 3t o 17 5 mm Hg. The volume of the noncontused hemispheric areas decreased by 13 8 mL whereas the specific gravity increased by 0.029 0.027%. The volume of contused hemispheric tissue increased by 5 5 mL without any concomitant change in density. There was a wide interindividual variability in the response of the noncontused hemispheric tissue with changes in specific gravity varying between 0.0124% and 0.0998%. Conclusions: Three days after traumatic brain injury, the bloodbrain barrier remains semipermeable in noncontused areas but not in contusions. Further studies are needed to tailor the use of hypertonic saline in patients with traumatic brain injury according to the volume of contusions assessed on computed tomography. (Crit Care Med 2006; 34:3029‐3033)

A skinning approach for dynamic 3D mesh compression: Research Articles

Abstract: This paper proposes a novel approach for 3D mesh compression, based on a skinning animation technique. The core of the proposed method is a piecewise affine predictor coupled with a skinning model and a DCT representation of the residuals errors. The experimental evaluation shows that the proposed skinning-based encoder outperforms (with bitrates gains from 47p to 67p) GV, RT, MPEG-4/AFX-IC, D3DMC, PCA and Dynapack techniques. Copyright © 2006 John Wiley & Sons, Ltd.

Multi-Chart Geometry Video: A Compact Representation for 3D Animations

Abstract: This paper introduces a new compression scheme, so- called Multi-Chart Geometry Video (MCGV), for 3D dynamic meshes with constant connectivity and time-varying geometry. The core of the proposed method is a piecewise affine predictor coupled with a Multi-Chart Geometry IMage (MCGIM) representation of the residual errors. The mesh is first partitioned into vertex clusters whose motion can be accurately described by a unique 3D affine transform. The prediction errors are represented as MCGIMs which are compressed by using standardized image encoders such as JPEG and MPEG-4. The performances of our encoder are objectively evaluated on a data set of six animation sequences with various sizes, geometries and topologies, and exhibiting both rigid and elastic motions. The experimental evaluation shows that the proposed MCGV achieves up to 60% lower compression distortions than the geometry video approach, while outperforming (with 30% to 94% lower distortions) the RT, MPEG-4IAFX-IC, D3DMC, PCA and Dynapack techniques.

Computed tomography-estimated specific gravity of noncontused brain areas as a marker of severity in human traumatic brain injury.

Abstract: In this study, we assessed the relationship between brain estimated specific gravity (eSG) and clinical symptoms, therapeutic intensity level, and outcome in human traumatic brain injury (TBI). Brain weight, volume, and eSG of the noncontused hemispheric areas were measured from computed tomography

Temporal DCT-based compression of 3D dynamic meshes

Abstract: This paper introduces a new compression scheme for 3D dynamic meshes with constant connectivity and time-varying geometry. The proposed approach, referred to as Temporal-CT encoder (TDCT), combines a piecewise affine prediction scheme with a temporal DCT-based compression of the prediction errors. Experiments show that TDCT achieves up to 70% and 54% lower compression distortions than the GV and MCGV approaches, while outperforming (47% to 95% lower distortions) RT, MPEG-4/AFX-IC, D3DMC and Dynapack techniques.

Assessment of airway remodeling in asthma: volumetric versus surface quantification approaches

Abstract: This paper develops a volumetric quantification approach of the airway wall in multi-detector computed tomography (MDCT), exploiting a 3D segmentation methodology based on patient-specific deformable mesh model. A comparative study carried out with respect to a reference 2D/3D surface quantification technique underlines the clinical interest of the proposed approach in assessing airway remodeling in asthmatics and in evaluating the efficiency of therapeutic protocols.

Ensuring multimedia content enrichment by means of data hiding techniques

Abstract: Nowadays, a large variety of emerging applications (clickable video, interactive high definition television, intelligent interfaces) do not only processes the multimedia content (audio, video, 3D, ) but some additional data directly connected to it, as well This enrichment information is usually transmitted and stored as an additional independent stream (metadata) Such an approach can be restrictive sometimes, mainly for the networks/applications with strict bandwidth and/or protocol constraints An alternative solution is advanced and discussed in this paper The principle consists in transmitting the metadata via in-band channels obtained by means of data hiding (watermarking) techniques The challenge is to design data hiding techniques reaching the trade off among transparency (the enrichment process should not alter the perceptual quality of the host media), robustness (possibility to recover the metadata at the end user even when high distortions occur through the channel) and data payload (the amount of metadata which can be inserted) The paper investigates the feasibility of such techniques by evaluating the maximal data payload (the watermarking capacity) under given robustness and transparency constraints The results are compared to the resources needed by some existing enrichment applications The experiments are carried out in collaboration with the French mobile service operator SFR (Vodafone Group) and consider video sequences watermarked in the DWT domain

A skinning prediction scheme for dynamic 3D mesh compression

Abstract: This paper presents a new prediction-based compression technique for dynamic 3D meshes with constant connectivity and time-varying geometry. The core of the proposed algorithm is a skinning model used for motion compensation. The mesh is first partitioned within vertex clusters that can be described by a single affine motion model. The proposed segmentation technique automatically determines the number of clusters and relays on a decimation strategy privileging the simplification of vertices exhibiting the same affine motion over the whole animation sequence. The residual prediction errors are finally compressed using a temporal-DCT representation. The performances of our encoder are objectively evaluated on a data set of eight animation sequences with various sizes, geometries and topologies, and exhibiting both rigid and elastic motions. The experimental evaluation shows that the proposed compression scheme outperforms state of the art techniques such as MPEG-4/AFX, Dynapack, RT, GV, MCGV, TDCT, PCA and RT compression schemes.

Three-dimensional reconstruction of the bronchial tree in volumetric computerized tomography: application to computerized tomography bronchography

Abstract: We present a new method for computerized tomography (CT)-based investigation of pulmonary airways. The developed approach is based on a fully automated 3-D reconstruction of the bronchial tree from volumetric spiral CT data. The 3-D reconstruction procedure combines mathematical morphology-based 2-D segmentation, performed on axial images, together with 3-D topology-based restoration and filtering. The 3-D bronchial tree is reconstructed up to the sixth subdivision order and is investigated by using a volume-rendering technique, where bronchi voxels are assigned the gray-level value of their projection in the original CT images. Such a visualization modality, referred to as CT bronchography, provides radiologists with a perception of the sole 3-D bronchial tree structure and preserves the original data contrast. Tested on a data set corresponding to 20 clinical examinations, the proposed method shows robustness with respect to various pathologies such as stenosis, bronchiectasis, mucoid impactions, and infiltrative diseases. It emphasizes the interest in considering CT bronchography as a complementary tool for clinical diagnosis and follow-up of airway diseases.

Interactivity, reactivity and programmability: advanced MPEG-4 multimedia applications

Abstract: This paper presents recent developments on the creation of advanced iDTV applications with MPEG-4 technologies. Elaborated within the framework of the European ITEA Jules Verne project the proposed Encyclopedia application exploits sophisticated multimedia representations enriched with dynamic behaviors, enabled by the programmatic functionality supported by the MPEG-4 standard. A comprehensive integration of the 3D graphics and audio-visual MPEG technologies together with the Java programming is achieved.

Region-based statistical segmentation using informational active contours

Abstract: Hybrid variational image segmentation techniques, involving energy functionals which combine contour- and region-based terms, have been actively investigated due to their ability to jointly integrate shape and texture cues about scene objects. Minimizing these functionals can be efficiently achieved using curve evolution techniques, yielding region competition models along the deforming segmentation boundaries. Within this framework, this paper presents a novel region-based statistical active contour approach to segmentation, refered to as info-snakes. Here, the segmentation problem is expressed as the maximization of an information-theoretic similarity measure between the image luminance distribution, and the label distribution of a regional template defining a multi-object geometric prior model, subject to regularization constraints on region boundaries. The probability densities associated with luminance distributions within each template region are estimated using a nonparametric Parzen technique, which avoids resorting to prior assumptions on image statistics or to a training phase. We shall focus our attention on the Ali-Silvey class of information measures, and derive the corresponding gradient flows over nonparametric smooth curve spaces. As expected, the evolution equations for the template boundaries interpret as a statistical region competition model, promoting statistically consistent regions relative to the chosen information metrics. An efficient implementation using a multiphase level set technique is finally provided. Experiments on a cardiac perfusion MRI dataset are presented, demonstrating the relevance of info-snakes for implementing computer-assisted diagnosis tools in cardiology.

2D approaches to 3D watermarking: state-of-the-art and perspectives

Abstract: With the advent of the Information Society, video, audio, speech, and 3D media represent the source of huge economic benefits. Consequently, there is a continuously increasing demand for protecting their related intellectual property rights. The solution can be provided by robust watermarking, a research field which exploded in the last 7 years. However, the largest part of the scientific effort was devoted to video and audio protection, the 3D objects being quite neglected. In the absence of any standardisation attempt, the paper starts by summarising the approaches developed in this respect and by further identifying the main challenges to be addressed in the next years. Then, it describes an original oblivious watermarking method devoted to the protection of the 3D objects represented by NURBS (Non uniform Rational B Spline) surfaces. Applied to both free form objects and CAD models, the method exhibited very good transparency (no visible differences between the marked and the unmarked model) and robustness (with respect to both traditional attacks and to NURBS processing).

MPEG-4 3D graphics: from specifications to the screen

Abstract: This paper presents a novel implementation of a 3D rendering engine able to display 3D graphics MPEG-4 objects. By using the MPEG-4 SDK (Software Developer Kit), the 3D objects are first decoded and the MPEG-4 scene graph structure is filed. We introduce a scene manager able to address in an optimized manner the rendering requirements. It is developed as part of the rendering engine and it enables to create an appropriate form representation of the data resources. The novel concept implemented here is to consider the scene management with respect to the rendering constraints and not to the representation of the data as in a usual MPEG-4 approach. This paper describes the software communication procedures between the MPEG-4 SDK and the rendering scene management in the case of static and animated (skinned) object and some results dealing with the representation of an articulated model illustrate the performances of the developed approach.

Automated volumetric approach for quantifying bronchial wall remodeling in MDCT

Abstract: Follow-up studies of bronchial wall remodeling in asthmatics based on multi-detector computed tomography (MDCT) imaging is the emerging modality for therapy assessment. While providing statistically significant quantification of global variation before/after treatment, the employed cross-section-area estimation techniques cannot guarantee the absolute accuracy of point-by-point estimation. Such uncertainty comes from the impossibility to define an accurate cross-sectional plane of a bronchus at locations where the notion of central axis is questionable. In order to overcome such limitation, this paper develops an original automated volumetric approach for bronchial wall quantification involving a successive model-based 3D reconstruction of the inner and outer bronchial wall surfaces. The inner surface is segmented by means of strong 3D morphological filtering and model-fitting. An optimal geometrico-topological model is generated by using a restricted Delaunay triangulation approach. The model is then dynamically deformed in the surface normal direction, under the constraint of local energy minimization acting at each evolving vertex. The energy potentials oppose a mesh-derived elastic component combining topological and geometric features in order to preserve shape regularity, and an expansion potential exploiting image characteristics. The deformation process both adapts the mesh resolution and handles topology changes and auto-collisions. The developed 3D modeling stabilizes the deformation at the level of the outer surface of the bronchial wall and provides robustness with respect to bronchus-blood vessel contacts, where image data is irrelevant. The accuracy of the volumetric segmentation approach was evaluated with respect to 3D mathematically-simulated phantoms of bronchial subdivisions. Comparisons with recent 2D techniques, carried out on simulated and real MDCT data showed similar performances in cross-section wall area quantification. The benefit of using volumetric versus cross-section area quantification is finally argued in the context of bronchial reactivity and wall remodeling follow-up.

Multimedia robust watermarking: commercial application and standardisation approaches

Abstract: The Information Society around us today can manipulate (copy, transmit) all types of information easier than ever before. For most users, the bulk of the processed information is multimedia data (image, music, video, etc.). Several solutions for the intellectual right protection have been tried out. But most of them also restrict the very rights of authorised users. Watermarking proved itself to be a powerful, yet un-restraining solution to this problem. The content is protected by imperceptibly inserting some copyright and/or tracking data into the multimedia object, so that these data cannot be removed. Moreover, watermarking can also be used for preventing other types of abuse. While ignoring the related scientific and legal issues, this paper reports on the commercial and standardisation approaches to watermarking.

Data hiding techniques: an innovative approach to video interactivity

Abstract: Nowadays, the multimedia consumer is introduced to an entirely new multimedia concept, namely the enriched media. The versatility of the digital networks alongside with the new, intelligent terminals, have allowed the creation and distribution of the classic media types enhanced with additional content information, introducing new features, from the trivial media-related information (e.g. EXIF data for the still images, ID3 tag for the MP3 music) to display/play information and interactive behaviour. However, these new features are hardly available on classic distribution networks. This paper presents an innovative approach to multimedia enrichment, allowing not only the distribution of this type of media over older networks, but its compact and unitary handling as well. The enriching information is inserted directly into the host media by means of data hiding techniques. The experiments were carried out in cooperation with the SFR (Vodafone group) wireless service provider in France.

BronWall: a software system for volumetric quantification of the bronchial wall remodeling in MDCT

Abstract: This paper develops an original volumetric quantification approach of the bronchial wall remodeling, based on MDCT acquisitions prior/post-medication delivery. The methodology is implemented as a software system -BronWall- integrating 3D segmentation, interaction, navigation, representation and 2D/3D quantification facilities. Such a system provides higher robustness with respect to the existing quantification approaches and MDCT acquisition protocol variability. BronWall may thus become a clinical tool for estimating the impact of therapeutic protocols designed to reverse the airway remodeling induced by chronic obstructive pulmonary diseases.

Handling multilingual content in digital media: a critical analysis

Abstract: This document expresses and analyzes the need to define a generic method for representing multilingual information in multimedia data. It describes the basic requirements that would bear upon such representations and establishes the potential link with ISO committee TC 37/SC 4 (Language Resource Management) and with XMT (eXtended MPEG-4 Textual format).