In recent years, the impressive progress performed in imaging, computational and technological fields have made possible the emergence of image-guided radiation therapy (IGRT) and adaptive radiation therapy (ART). The accuracy in radiation dose delivery reached by IMRT offers the possibility to increase locoregional dose-intensity, potentially overcoming the poor tumor control achieved by standard approaches. However, before implementing such a technique in clinical routine, a particular attention has to be paid at the target volumes definition and delineation procedures to avoid inadequate dosage to TVs/OARs. In head and neck squamous cell carcinoma (HNSCC), the GTV is typically defined on CT acquired prior to treatment. However, providing functional information about the tumor, FDG-PET might advantageously complete the classical CT-Scan to better define the TVs. Similarly, re-imaging the tumor with optimal imaging modality might account for the constantly changing anatomy and tumor shape occurring during the course of fractionated radiotherapy. Integrating this information into the treatment planning might ultimately lead to a much tighter dose distribution. From a methodological point of view, the delineation of TVs on anatomical or functional images is not a trivial task. Firstly, the poor soft tissue contrast provided by CT comes out of large interobserver variability in GTV delineation. In this regard, we showed that the use of consistent delineation guidelines significantly improved consistency between observers, either with CT and with MRI. Secondly, the intrinsic characteristics of PET images, including the blur effect and the high level of noise, make the detection of the tumor edges arduous. In this context, we developed specific image restoration tools, i.e. edge-preserving filters for denoising, and deconvolution algorithms for deblurring. This procedure restores the image quality, allowing the use of gradient-based segmentation techniques. This method was validated on phantom and patient images, and proved to be more accurate and reliable than threshold-based methods. Using these segmentation methods, we proved that GTVs significantly shrunk during radiotherapy in patients with HNSCC, whatever the imaging modality used (MRI, CT, FDG-PET). No clinically significant difference was found between CT and MRI, while FDG-PET provided significantly smaller volumes than those based on anatomical imaging. Refining the target volume delineation by means of functional and sequential imaging ultimately led to more optimal dose distribution to TVs with subsequent soft tissue sparing. In conclusion, we demonstrated that a multi-modality-based adaptive planning is feasible in HN tumors and potentially opens new avenues for dose escalation strategies. As a high level of accuracy is required by such approach, the delineation of TVs however requires a special care.

A numerical code for solving the time-dependent incompressible 3D Navier-Stokes equations with finite volumes on overlapping staggered grids in cylindrical and rectangular geometry is developed. In the code, written in FORTRAN, the momentum equation for the velocity is solved by projection method and Poisson equation for the pressure is solved by ADI implicit method in two directions combined with discrete fast Fourier transform in the third direction. A special technique for overcoming the singularity on the cylinder's axis is developed. This code, taking into account dependence upon temperature of the viscosity, density and surface tension of the liquid, is used to study the fluid motion in a cylinder with free cylindrical surface (under normal and zero-gravity conditions); and in a rectangular closed cell with a source of thermocapillary convection (bubble inside attached to one of the cell's faces). They are significant problems in crystal growth and in general experiments in fluid dynamics respectively. Nevertheless, the main study is dedicated to the liquid bridge problem. The development of thermocapillary convection inside a cylindrical liquid bridge is investigated by using a direct numerical simulation of the 3D, time-dependent problem for a wide range of Prandtl numbers, Pr = 0.01 - 108. For Pr > 0.08 (e.g. silicon oils), above the critical value of temperature difference between the supporting disks, two counter propagating hydrothermal waves bifurcate from the 2D steady state. The existence of standing and traveling waves is discussed. The dependence of viscosity upon temperature is taken into account. For Pr = 4, 0-g conditions, and for Pr = 18.8, 1-g case with unit aspect ratio an investigation of the onset of chaos was numerically carried out. For a Pr = 108 liquid bridge under terrestrial conditions , the appearance and the development of thermoconvective oscillatory flows were investigated for different ambient conditions around the free surface. Transition from 2D thermoconvective steady flow to a 3D flow is considered for low-Prandtl fluids (Pr = 0.01) in a liquid bridge with a non-cylindrical free surface. For Pr < 0.08 (e.g. liquid metals), in supercritical region of parameters 3D but non-oscillatory convective flow is observed. The computer program developed for this simulation transforms the original non-rectangular physical domain into a rectangular computational domain. A study of how presence of a bubble in experimental rectangular cell influences the convective flow when carrying out microgravity experiments. As a model, a real experiment called TRAMP is numerically simulated. The obtained results were very different from what was expected. First, because of residual gravity taking place on board any spacecraft; second, due to presence of a bubble having appeared on the experimental cell's wall. Real data obtained from experimental observations were taken for the calculations.

L'objectif de cette thèse consiste en l'étude d'une stratégie de contrôle actif à faible autorité avec comme application le contrôle actif du rayonnement acoustique d'une plaque. Depuis l'essor du contrôle actif, son application aux problèmes acoustiques et vibracoustiques a été investiguée par de nombreux chercheurs, exploitant soit la théorie du contrôle optimal, soit des approches originales basées plus particulièrement sur la physique. Des notions spécifiques au contrôle vibroacoustique ont été développées comme, par exemple, les modes radiatifs pouvant caractériser le rayonnement acoustique d'une plaque d'une manière adaptée au contrôle. Le contrôle actif à faible autorité, pour lequel le Laboratoire de Structures Actives a développé une expertise dans le domaine de l'amortissement et du contrôle actif des vibrations, est une solution attractive par sa simplicité de mise en oeuvre. Le plus souvent implémenté sous la forme d'un contrôle décentralisé constitué de boucles indépendantes, le contrôle à faible autorité bénéficie de certaines garanties de stabilité et de robustesse. Bien que notre stratégie de contrôle puisse s'appliquer à n'importe quel type de plaque, l'application considérée dans ce travail a été motivée par le contexte socio-économique actuel en rapport avec les nuisances acoustiques. Il était en effet intéressant d'évaluer la stratégie de contrôle pour le problème de la transmission acoustique d'un vitrage. La stratégie de contrôle se divise en deux étapes. Tout d'abord le développement d'un capteur unique destiné à fournir une mesure représentative du bruit rayonné par une plaque en basse fréquence. Deux capteurs de vitesse volumétrique (l'un discret, l'autre distribué) ont ainsi été développés et évalués expérimentalement. Ensuite, une procédure d'optimisation de l'emplacement d'un ensemble d'actionneurs pilotés en parallèle est proposée. L'objectif de cette phase d'optimisation est de forcer la réponse fréquentielle du système à posséder les propriétés d'un système colocalisé. La stratégie de contrôle est ensuite évaluée sur deux structures expérimentales. / This thesis is concerned with a low authority active control strategy applied to the sound radiation control of a baffled plate. Since the development of active control , numerous researchers have studied its application to acoustical or vibroacoustical problems using either the modern control theory or other methods based rather on the understanding of the physics of the problem. Vibroacoustical active control has lead to the definition of radiation modes allowing to describe the radiated sound of a plate in an appropriate manner for active control purposes. Low autorithy control (LAC), for which the Active Structures Laboratory has gained an expertise for active vibration control applications is an interesting solution for its implementation simplicity. Most of the time it consists of several decentralized control loops, and benefits from guaranteed stability and robustness properties. Although our control strategy can be applied to any kind of plates, the application considered here has been motivated by the present socio-economical context related to noise annoyances. The active control strategy has been applied the problem of the sound transmission loss of glass plates (windows). This strategy is in two steps : first a volume velocity sensor is developed as to give a measure representative of the radiated sound at low frequencies. Two sensors have been developed (one discrete and one distributed) and experimentally tested. Next, an optimisation strategy is proposed which allow to locate on the plate a set of several actuators driven in parallel. The goal of this optimisation task is to obtain an open-loop frequency response which behave like a collocated system. The control strategy is finally evaluated on two plate structures.

<p>Case hardening distortions are a major problem for gear manufacturers. The aim of the current work is to create a simulation model, able to predict how and when case hardening distortions arise. The results presented in this thesis form a basis for such a model.</p><p>Two case hardening steels, with base carbon contents of 0.20 and 0.21 % C were studied using dilatometer experiments. One of them was carburized to 0.36, 0.52 and 0.65 % C in order to investigate the influence of carbon content. Experiments were performed during both isothermal and continuous heating and cooling conditions. The results were used to evaluate phase transformations, heat expansion behaviors and phase transformation strains. The expansion behavior of the material was modeled as a function of temperature, carbon content and phase fractions. The phase transformations to martensite and bainite were modeled, using the Koistinen-Marburger equation and a transformation rate equation based on Austin-Rickett kinetics, respectively. Experiments were simulated using the COMSOL Multiphysics software, to verify the model with respect to martensite and bainite transformations, heat expansion behavior and phase transformation strains.</p>

Computed Tomography (CT) is a medical imaging modality which acquires anatomical data via the unique x-ray attenuation of materials. Yet, some clinically important materials remain difficult to distinguish with current CT technology. Spectral CT is an emerging technology which acquires multiple CT datasets for specific x-ray spectra. These spectra provide a fingerprint that allow materials to be distinguished that would otherwise look the same on conventional CT. The unique characteristics of spectral CT data motivates research into novel visualization techniques. In this thesis, we aim to provide the foundation for visualizing spectral CT data. Our initial investigation of similar multi-variate data types identified intermixing as a promising visualization technique. This promoted the development of a generic, modular and extensible intermixing framework. Therefore, the contribution of our work is a framework supporting the construction, analysis and storage of algorithms for visualizing spectral CT studies. To allow evaluation, we implemented the intermixing framework in an application called MARSCTExplorer along with a standard set of volume visualization tools. These tools provide user-interaction as well as supporting traditional visualization techniques for comparison. We evaluated our work with four spectral CT studies containing materials indistinguishable by conventional CT. Our results confirm that spectral CT can distinguish these materials, and reveal how these materials might be visualized with our intermixing framework.

No description available.

The rapid proliferation of 3D volume data, including MRI and CT scans, is prompting the search within computer graphics for more effective volume visualisation techniques. Partially because of the traditional association with medical subjects, concepts borrowed from the domain of scientific illustration show great promise for enriching volume visualisation. This thesis describes the first general system dedicated to creating user-directed, variable-detail, scientific illustrations directly from volume data. In particular, using volume segmentation for explicit abstraction in non-photorealistic volume renderings is a new concept. The unique challenges and opportunities of volume data require rethinking many non-photorealistic algorithms that traditionally operate on polygonal meshes. The resulting 2D images are qualitatively different from but complementary to those normally seen in computer graphics, and inspire an analysis of the various artistic implications of volume models for scientific illustration.

There have been reports on the use of Ultrasound (US) for monitoring fracture repair and for measuring muscle volume. Change in muscle mass is a useful bio-marker for monitoring the use and disuse of muscle, and the affects of age, disease and injury. The main modality for imaging bone is X-ray and for muscle volume Magnetic Resonance (MR). Previous studies have shown US to have advantages over X-ray and MR. US can image all stages of the fracture repair process and can detect signs of healing 4-6 weeks before X-ray allowing earlier detection of possible complications. Compared to MR, US is less resource intensive, easier to access and also has fewer exclusion criteria for patients. Despite these advantages, the limited field of view that US can provide results in high operator dependency for scan interpretation and also for length and volume measurements. Three-dimensional Ultrasound (3D US) has been developed to overcome these limitations and has been used to provide extended field of view images of the foetus and the heart and to obtain accurate volume measurements for organs. In this thesis it is hypothesized that 3D US can provide a more comprehensive method of imaging fracture repair than X-ray and is also a viable alternative to MR for determining muscle volumes in vivo. Initially, an electromagnetically (EM) tracked 3D US system was evaluated for clinical use using phantom-based experiments. It was found that the presence of metal objects in or near the EM field caused distortion and resulted in errors in the volume measurements of phantoms of up to ±20%. An optically tracked system was also evaluated and it was found that length measurements of a phantom could be made to within ±1.3%. Fracture repair was monitored in five patients with lower limb fractures. Signs of healing were visible earlier on 3D US with a notable, although variable, lag between callus development on X-ray compared to 3D US. 3D US provided a clearer view of callus formation and the changes in density of the callus as it matured. Additional information gained by applying image processing methods to the 3D US data was used to develop a measure of callus density and to identify the frequency dependent appearance of the callus. Volume measurements of the rectus femoris quadricep muscle were obtained using 3DUS from eleven healthy volunteers and were validated against volume measurements derived using MR. The mean difference between muscle volume measurements obtained using 3D US and MR was 0.53 cm3 with a standard deviation of 1.09 cm3 and 95% confidence intervals of 0.20 - 1.27 cm3 In conclusion, 3D US demonstrates great potential as a tool for imaging components of the musculoskeletal system and as means of measuring callus density.

Les composants passifs électro-acoustiques sont des éléments critiques des architectures RF. Les plus représentés sont les filtres à ondes acoustiques de surface (SAW) ou de volume (BAW), qui permettent le filtrage RF (filtre d’antenne). Pour le filtrage de canal, les solutions SAW sont actuellement en place, bien que des travaux récents aient montré l’intérêt des résonateurs à ondes de Lamb pour ce type d’application. Ces derniers composants présentent l’avantage d’être compatibles avec une technologie de fabrication de filtres BAW réalisés sur membrane suspendue (FBAR), permettant une co-intégration des deux types de composants à moindre coût. Toutefois, le choix technologique de STMicroelectronics et du CEA-Leti s’est porté sur une technologie de résonateurs BAW réalisés sur miroir de Bragg (SMR). Le but de cette thèse est donc de démontrer la possibilité de réaliser des résonateurs reprenant le principe des résonateurs à ondes de Lamb, mais co-intégrables avec des BAW-SMR. Après une présentation de l’état des lieux des composants électromécaniques utilisés dans les architectures RF et des diverses propositions de dispositifs semblables présentes dans la littérature, nous abordons une étude théorique du principe de fonctionnement de ce type de composants, ce qui nous permet d’en cerner les caractéristiques : coefficientsde couplage électromécaniques proches de ceux des résonateurs à ondes de Lamb, mais fonctionnement à des fréquences proches de celles des résonateurs BAW. Nous présentons ensuite les méthodes de dimensionnement employées. Enfin, nous présentons un procédé de réalisation proche de celui des BAWSMR fabriqués au CEA-Leti, mais adapté à nos composants. A l’issue de caractérisations électriques, nous sommes en mesure de présenter les premiers composants de ce type fonctionnels, et une liste d’améliorations possibles. Ces travaux ont permis des publications dans quatre conférences dont trois internationales, un journal, un dépôt de brevet d’invention et deux publications internes au laboratoire commun IEMN-STMicroelectronics. / Passive acoustic devices are enabling elements for RF architectures. Aside from the well known surface acoustic wave (SAW) and bulk acoustic wave (BAW) filters used for RF filtering, Lamb wave devices have recently been seen as an alternative to SAW devices currently used also for intermediate frequency filtering. These resonators are compatible with a membrane-based BAW technology (FBAR) and could thus be co-integrated with them with no additional cost. However, STMicroelectronics and CEALeti have focused their developments around BAW resonators using a Bragg mirror for acoustic isolation (SMR). Therefore, the aim of this work is to demonstrate the possibility of fabricating resonators close to Lamb wave resonators, but technologically compatible with a BAW-SMR technology. After reviewing the applications of electromechanical resonators in RF architectures and the proposals for the kind of resonators we are investigating available in the literature, we start with a theoretical investigation of these devices. This enables us to determine basic characteristics of these resonators: electromechanical coupling factors close to Lamb wave devices, but operation at frequencies close to BAW resonators. Then, we describe the design of demonstrators. Finally, we describe a fabrication process, similar to BAW-SMR fabrication process, which has provided to date the first operating devices using this principle. Electrical characterizations show that the fabricated resonators are functional, and we discuss possible improvements.This work led to publications in four conferences, (three international conferences), a paper, a patent and two internal publications at IEMN-STMicroelectronics common laboratory.

Modern medical imaging devices are able to generate highly detailed three-dimensional (3D) images of the skeleton. Computerized image processing and analysis methods, combined with real-time volume visualization techniques, can greatly facilitate the interpretation of such images and are increasingly used in surgical planning to aid reconstruction of the skeleton after trauma or disease. Two key challenges are to accurately separate (segment) bone structures or cavities of interest from the rest of the image and to interact with the 3D data in an efficient way. This thesis presents efficient and precise interactive methods for segmenting, visualizing, and analysing 3D computed tomography (CT) images of the skeleton. The methods are validated on real CT datasets and are primarily intended to support planning and evaluation of cranio-maxillofacial (CMF) and orthopedic surgery. Two interactive methods for segmenting the orbit (eye-socket) are introduced. The first method implements a deformable model that is guided and fitted to the orbit via haptic 3D interaction, whereas the second method implements a user-steered volumetric brush that uses distance and gradient information to find exact object boundaries. The thesis also presents a semi-automatic method for measuring 3D angulation changes in wrist fractures. The fractured bone is extracted with interactive mesh segmentation, and the angulation is determined with a technique based on surface registration and RANSAC. Lastly, the thesis presents an interactive and intuitive tool for segmenting individual bones and bone fragments. This type of segmentation is essential for virtual surgery planning, but takes several hours to perform with conventional manual methods. The presented tool combines GPU-accelerated random walks segmentation with direct volume rendering and interactive 3D texture painting to enable quick marking and separation of bone structures. It enables the user to produce an accurate segmentation within a few minutes, thereby removing a major bottleneck in the planning procedure.