Дисертації з теми "Imagerie à contraste élevé"
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Alagao, Mary Angelie. "Characterization and optimization of the Evanescent Wave Coronagraph." Electronic Thesis or Diss., Saint-Etienne, 2023. http://www.theses.fr/2023STET0060.
Direct imaging of exoplanets remains challenging due to the high contrast and the small angular separation between the star and the planet. It requires suppressing the blinding glare from the star and ensuring that the planet's faint light is not buried deep in various noises. Successful detection depends on the technological readiness and maturity of techniques and algorithms employed while considering the significant trade-offs on raw contrast, inner working angle, and throughput. One of its key components is the use of coronagraphs – instruments with the sole purpose of blocking/reducing the light from the star. This work presents a new type of Lyot coronagraph, invented by Dr. Yves Rabbia, that relies on the frustrated total internal reflection (FTIR) principle to suppress the starlight. This coronagraph is aptly called the Evanescent Wave Coronagraph (EvWaCo) owing to its nature that its focal plane mask, comprising a lens and a prism, reflects the off-axis source (planet) and transmits the on-axis source (star) by capturing the evanescent waves. This thesis aims to provide the reader with the groundwork that highlights EvWaCo's three main advantages: i) the mask is inherently achromatic, ii) the size of the mask is adjustable by changing the pressure between the lens and the prism, and iii) both the stellar light and the planet light can be collected simultaneously for low-order wavefront sensing, and proper stellar light centering. The performance of EvWaCo is assessed through experiments in a laboratory and then compared to numerical simulations. The experimental results show a raw contrast equal to a few 10-4 at 3 ��/�� over the full I-band (��c = 800 nm, ∆��/�� ≈ 20%) and at 4 ��/�� over the full R-band (��c = 650 nm, ∆��/�� ≈ 23%). The simulations confirm the achromatic rejection capability of EvWaCo as it showed a raw contrast of 10-4 at the same radial distance over both bandpasses. This thesis concludes with the status of its testbed and future perspectives
Sanalatii, Maryna. "Synthèse d'un champ acoustique avec contraste spatial élevé." Thesis, Le Mans, 2018. http://www.theses.fr/2018LEMA1005/document.
The goal of this thesis is the design of a transportable speaker system, able to generate a predefined and focused sound field with a high spatial contrast. This system has eventually to allow carrying out different types of studies, for example acoustic transmission loss tests or vibration tests in non-anechoic conditions. The minimization of the number of driven channels and the number of transducers is one of the main goals of the work. The choice of the number of sources and the selection of their optimal positions in order to generate a target acoustic field has no trivial solution. To answer this question, the proposed method is based on the decomposition of the source radiation into a series of independent orthogonal functions (the "radiation modes"), constructed numerically via a singular value decomposition of the impedance matrix. By filtering the evanescent terms, the far field can be reconstructed using a small number of terms. In addition, the method allows the estimation of an efficient flow distribution to generate the target field. With the proposed method having been scarcely studied in the literature, the first part of the thesis is devoted to the problem of the experimental validation of the direct method and the study of the main parameters that are influencing the result. The problem of sources positioning in order to synthesize a predefined and focused sound field is discussed in the second part of the thesis
Jullien, Aurélie. "Génération d'impulsions laser ultra-brèves et ultra-intenses à contraste temporel élevé." Phd thesis, Ecole Polytechnique X, 2006. http://tel.archives-ouvertes.fr/tel-00077486.
Le travail présenté consiste en l'étude théorique et expérimentale d'un filtre temporel basé sur un effet non linéaire du troisième ordre, agissant sur la polarisation de l'impulsion. Nous avons étudié plusieurs déclinaisons de ce principe. Le dispositif finalement retenu repose sur la génération d'une onde polarisée orthogonalement (XPW) dans des matériaux cristallins dont la susceptibilité non linéaire d'ordre trois est anisotrope. Ce filtre non linéaire a été testé sur différents systèmes femtosecondes et permet l'amélioration du contraste sur plusieurs ordres de grandeur, comme le confirment les mesures de profils temporels sur une grande dynamique réalisées après filtrage. Nous avons également conçu un dispositif pour optimiser l'efficacité de conversion du processus non linéaire, c'est-à-dire la transmission du filtre. Cette méthode consiste à générer des interférences constructives entre les signaux XPW émis dans des cristaux distincts. Dans ces conditions, l'efficacité de transmission théorique (supérieure à 20%) est atteinte expérimentalement et dans le même temps la stabilité du système est assurée. Nous avons enfin démontré que le filtre préserve, voire améliore, les qualités spectrales et spatiales de l'impulsion.
Ces résultats sont donc particulièrement prometteurs et permettent d'envisager l'implémentation définitive du filtre dans les systèmes femtosecondes.
Jullien, Aurélie. "Génération d'impulsions laser ultra brèves et ultra intenses à contraste temporel élevé." Palaiseau, Ecole polytechnique, 2004. http://www.theses.fr/2006EPXX0013.
Novell, Anthony. "Imagerie de contraste ultrasonore avec transducteurs capacitifs micro-usinés." Phd thesis, Tours, 2011. http://tel.archives-ouvertes.fr/tel-00665141.
Bouakaz, Ayache. "Produits de contraste ultrasonore : évaluation acoustique in vitro et application." Lyon, INSA, 1996. http://www.theses.fr/1996ISAL0058.
It's usually more difficult for a radiologist to interpret ultrasonic images than other records issued from other imaging modalities. Indeed, the ultrasonic record has no familiar landmarks for the uninitiated observer. As for other imaging techniques, the use of contrast agents could be considered. Typically, contrast ultrasound involves the injection of echo-producing microbubbles into the bloodstream to enhance the ultrasound echogenicity of a certain structure in the body. In the first part of this study, we proposed a theoretical approach for acoustic characterization of ultrasound contrast agents. Simultaneously, an experimental procedure was developed to quantify the ultrasonic properties of contrast agents in vitro. This was carried out by determining their acoustic parameters. The backscatter coefficient (BC), attenuation coefficient and scattering to attenuation ratio (STAR) were defined to quantify the ultrasonic effectiveness of the contrast agent. The experimental conditions correspond to the clinical reality. The experimental determination of ultrasonic properties is important for an appropriate use of the contrast agent. Afterwards, a method is presented and used to determine the acoustic contribution of a contrast agent to the image enhancement. Optimal values of the acoustic properties necessary to get a visible enhancement of the image are deduced. At last, we propose a newer clinical application using contrast agent. This has been done in intravascular echography and the contrast has been proved useful for this application
Hoeffel, Christine. "Echographie de contraste et microcirculation tissulaire abdominale. Aspects fondamentaux et applications cliniques." Reims, 2009. http://theses.univ-reims.fr/exl-doc/GED00001104.pdf.
The aim of this work was to study the potential for contrast-enhanced functional ultrasound imaging (Cefui) to assess the abdominal microcirculation, according to three major axes of research: 1) The first axis consisted in proposing and validating a new method improving non invasive contrast-enhanced renal blood flow measurements, using the mean signal intensity in a feeding artery in order to normalize contrast-enhanced renal blood flow estimation. However, while these ex vivo results suggest that this technique has great potentials, other parameters, mainly ultrasound beam attenuation, must be taken into account to obtain reproducible measurements. 2) The second axis consisted in evaluating qualitative abdominal Cefui for tumoral detection. For the detection of liver metastases from carcinoid tumor, the first study reports sensitivity values for contrast-enhanced ultrasound similar to those obtained with enhanced computed tomography. The second study demonstrates that Cefui provides high specificity and predictive values for the early detection of residual tumor after radiofrequency ablation of renal tumors even though its sensitivity remains lower than that of contrast-enhanced CT. 3) The third axis deals with added diagnostic value in terms of characterization of renal tumors of quantitative assessment of tumor perfusion compared to that of qualitative analysis. Abdominal Cefui has unique advantages including low cost, availability, absence of renal toxicity and radiation, and excellent temporal resolution. However, it still requires improvements and standardization to be reproducible and be transferred to the clinical setting. It may somehow yield quantitative information with respect to abdominal organs microcirculation. Further studies correlating Cefui results with those of other functional imaging methods are needed
Clauzon, Vivien. "Analyse de schémas d'ordre élevé pour les écoulements compressibles." Clermont-Ferrand 2, 2008. http://www.theses.fr/2008CLF21821.
Durning, Bruno. "Simulation, estimation spectrale et imagerie des agents de contraste ultrasonores." Lyon 1, 2006. http://www.theses.fr/2006LYO10097.
In this work, we contribute to make ultrasound contrast agent simpler and more effective to use. First we developed a Simulator of Echo Contrast Imaging (SECI). SECI can simulate ultrasound imaging with contrast agent. It takes into account the probe, the propagating medium, the individual, non linear, response of each bubble. Simulations of bubbles alone, have also been performed, at different MI, transmit frequency, and radius. Then, we validate SECI by comparison with in-vitro experiments. An experimental study of the influence of the MI over the contrast agent behavior has been done. Finally, visualization techniques, based on spectral estimation, auto-regressive modelization, and atomical projection have been tested on in-vitro and in-vivo acquisition
Beaulieu, Mathilde. "Imagerie optique à très haut contraste : une approche instrumentale optimale." Thesis, Université Côte d'Azur (ComUE), 2017. http://www.theses.fr/2017AZUR4040/document.
This thesis aims to optimize high-contrast imaging performance in visible and near infrared for exoplanet detection. The main study focuses on high-contrast at small separation, to image exoplanets in their habitable zone. This direct detection is achievable with the next Extremely Large Telescopes and with the development of coronagraph providing high performance at small separation. The approach adopted for this study creates a high-contrast region (a dark hole) with the combination of coronagraphy and wavefront shaping (wavefront control of both phase and amplitude with 2 deformable mirrors) but is limited by the Fresnel propagation of phase aberrations. The goal of this work is to define the wavefront shaping limitation in optical configuration (deformable mirrors location, component optical quality, beam diameter). A semi-analytic approach followed by a Monte-Carlo analysis of numerical end-to-end simulations is studied, resulting in the definition of the optimal configuration. Results are then applied to SPEED, a test bench to optimize and test high-contrast imaging at small separation with a segmented pupil. Another aspect of this thesis is a contribution to a stability study to treat the temporal stability as a crucial parameter in high-contrast imaging instrumentation, at the conception level. A preliminary work is initiated during the thesis to analyse the stability of the measuring instrument itself. A metrology tool and its thermal behaviour are thus studied. Finally, the last part of this thesis is a performance analysis of a new differential imaging technique, developed to improve high contrast with observations with different diaphragm sizes
Puong, Sylvie. "Imagerie du sein multispectrale avec injection de produit de contraste." Paris 11, 2008. http://www.theses.fr/2008PA112285.
During cancer development, angiogenesis occurs to support tumour growth. Contrast enhanced breast imaging takes advantage of this physiological phenomenon to enfance lesion visibility, by intravenously injecting a contrast medium into the blood. The present work focuses on multispectral methods which consist in the combination of images acquired with different spectra in order to generate a functional image of the breast neovascularisation. Our aim is to develop contrast enhanced multispectral breast imaging techniques, and especially, dual-energy contrast enhanced mammography and tomosynthesis. First, we present a model of the imaging system and the method of image combination which results in functional images of the neovascularisation. Then, a study of the optimal acquisition parameters is performed, in order to maximize the contrast medium visibility with respect to the patient dose. Contrast medium quantification is also investigated, as we analyze the influence of scattered radiation, variation of breast thickness and limited z resolution for tomosynthesis. First approach for correction of their effects are presented. Finally, results are detailed on a clinical study on dual energy contrast enhanced mammography, conducted at the Institut Gustave Roussy and Institut Curie, which allowed a first comparison of this application with conventional mammography and ultrasound
Perez, Laurence. "Les produits de contraste en IRM : biocompatibilité et sécurité." Paris 5, 1995. http://www.theses.fr/1995PA05P155.
Jeunehomme, Fanny. "Mammographie numérique avec injection de produit de contraste." Paris 11, 2005. http://www.theses.fr/2005PA112025.
It is well-established that the growth and metastatic potential of tumors is proportional to the extent of surrounding angiogenesis. Various imaging techniques, in particular Magnetic Resonance Imaging, are used to monitor the angiogenesis by analyzing contrast uptake. The introduction of digital mammography systems opens the way to Contrast-Enhanced Digital Mammography (CEDM). This thesis deals with the modeling and the optimization of the acquisition of contrast enhanced mammograms and with the analysis of contrast uptake in CEDM sequences. On the acquisition side, a method for optimizing the X-ray acquisition spectra that maximizes the contrast medium visibility is presented. Then a calibration method is proposed, which ensures the spatial and temporal uniformity of the acquisition system response. Concerning the analysis of the contrast uptake in the CEDM sequences, the main noise sources and the associated artifacts are characterized and solutions for putting them under control are proposed. A Support Vector Machine classification method of the breast tissues based on uptake kinetics is also proposed. In the last part of the document, a CEDM clinical study led at the Institut Gustave Roussy (France) is presented that demonstrates the clinical potential of this new approach
Thiré, Nicolas. "Photodynamiques moléculaires sondées par imagerie de vecteurs vitesses et génération d'harmoniques d'ordre élevé." Phd thesis, Toulouse 3, 2011. http://thesesups.ups-tlse.fr/1403/.
This thesis deals with the study of ultrafast phenomena, particularly the relaxation dynamics initiated by a femtosecond pulse (10-15 s). In the first part, velocity map imaging was used to study two systems: methyl iodide (CH3I), in its first excited Rydberg state and tetrathiafulvalene (TTF -C6H4S4). In the TTF, the aim is to characterize the two major absorption bands at 300 nm. During the study of the predissociation of CH3I, the vibrational distribution of the CH3 fragment was characterized,whereas as far as the TTF is concerned bond strength of the dimer was extracted. The interpretation of photoelectron spectra of CH3I provides a good understanding of the dynamics from and/or in resonance with states near the ionization potential. In the second part, the electronic structure of atom or molecule is probed by high order harmonics generation (HHG). The minimum of the total photoionization cross section of argon (Cooper minimum) was observed and studied in the harmonic spectrum. This study allowed, among other things, for the design of a reliable and comprehensive theoretical model. Then the HHG in a chiral molecule: the fenchone (C10H16O), clearly showed the sensitivity of the harmonic process to the chirality, while interacting with an elliptically polarized field. Finally, HHG was used to probe molecular dynamics initiated by a transient excitation grating at 400 nm in nitrogen dioxide (NO2). This at picosecond time scale : photodissociation, and femtosecond time scale : population transfer via a conical intersection
Thiré, Nicolas. "Photodynamiques moléculaires sondées par imagerie de vecteurs vitesses et génération d'harmoniques d'ordre élevé." Phd thesis, Université Paul Sabatier - Toulouse III, 2011. http://tel.archives-ouvertes.fr/tel-00663009.
Rognin, Nicolas Georges. "Outils de simulation et de quantification en imagerie de contraste échographique." Lyon 1, 2002. http://www.theses.fr/2002LYO10196.
Mulé, Sébastien. "Méthodologie pour l’évaluation de la microcirculation en imagerie ultrasonore de contraste." Paris 11, 2008. http://www.theses.fr/2008PA112033.
Contrast-enhanced ultrasound (CEUS) imaging is a modality of growing interest in human and small animal studies for the estimation of microcirculation parameters. Nevertheless, estimated microcirculation parameters are still impaired by several artefacts: the contrast agent concentration, microbubble attenuation and motion that is present in the acquisitions. The aim of this work is to propose a methodology for assessing microcirculation in small animal CEUS studies by investigating original methods to correct for these artefacts. An a posteriori frame selection method has been proposed. This method, based on a Principal Component Analysis and that integrates a priori information about the respiratory frequency, allows the selection of the frames acquired at the same respiratory phase. A method for estimating microbubble attenuation in vivo has also been developed. This method provides a dynamic microbubble-specific sequence without shadowing artefacts and therefore more reliable than available from original sequences. These methods, which have been implemented in a user friendly software, have been applied and validated in renal perfusion studies in a murine and a porcine model. Especially, their interest in assessing tumor microcirculation and the efficacy of an antiangiogenic treatment has been highlighted
Dedieu, Véronique. "Optimisation du contraste en imagerie par résonance magnétique nucléaire. Modélisation de l'action des agents de contraste et application au typage musculaire." Toulouse 3, 1996. http://www.theses.fr/1996TOU30069.
Brik, Mohab-Eddine. "Utilisation de nitroxydes comme agent de contraste en imagerie médicale par résonance magnétique nucléaire." Paris 11, 1987. http://www.theses.fr/1987PA112264.
IRM contrast mainly arises from the spin lattice or spin-spin relaxation time. This work deals with the synthesis of new nitroxide paramagnetic compounds and their utilization as contrast agents in NMR imaging. Their use permits a better caracterization of some organs and pathologies. The manuscript is divided in four chapters. 1- The synthesis and chemical characterization of fonctionalised nitroxydes. 55 products are obtained, 46 of them being new. 2- The biodistribution of these compounds is studied in rats through scintigraphy and E. P. R measurments. Five of them shows an intersting selectivity for organs as heart, lungs, kidneys and liver. 3- An "in vitro" N. M. R. Study is made to caracterize the magnetic properties of selected compouds through T1 measurments. 4- Last in final step N. M. R. Imaging is done on perfused rats in a mini imaging system working at 200 MHz. The quality and the specificity of the contrast agents are discussed
Rochefort, Ludovic de. "Imagerie dynamique et vélocimétrie IRM des gaz hyperpolarisés." Paris 11, 2006. https://tel.archives-ouvertes.fr/tel-00083287.
This work is part of a French project called R-MOD that aims at the development of a morpho-functional simulator of the upper and central airways. Here, hyperpolarized gas (HPG) MRI methods to visualize and quantify gas flows were developed to test the predictions of the simulator. To reach this goal, a dedicated MR-compatible device was built to administrate HPG in a controlled way and different imaging strategies were evaluated. A first qualitative approach was based on dynamic imaging of a HPG inspiration. An analysis of this type of experiment was achieved. The temporal evolution of the phenomenon is too high to be correctly imaged with the state-of-the-art techniques. Nevertheless, spatial distribution of the magnetization within the lung reaches an equilibrium state during a stationary inspiration. This equilibrium state depends on parameters that were explored both theoretically and experimentally through several dynamic imaging techniques. A second approach, more quantitative, is based on phase-contrast velocimetry combined with rapid radial imaging. The technique was first validated on known flow patterns (straight, curved and bifurcating pipes) and then applied on a realistic bronchial tree reconstructed from medical images and compared to computational fluid dynamics simulations. The 3 velocity components were measured within about 1 s, with 1-mm spatial resolution, and a precision of 1cm·s-1. Finally, in vivo feasibility was shown on a human trachea during an inhalation. This flow characterization technique based on HPG MRI is a promising tool for fluid dynamics studies and for related medical applications
Rougé-Labriet, Hélène. "Développement de l'imagerie X biomédicale en contraste de phase par tavelures." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAS031.
Osteoarticular diseases are one of the most common causes of chronic pain, but their diagnosis and understanding can be complex. Different imaging methods are available to describe joint conditions such as radiography, MRI, CT scan or ultrasound, but none of them can depict all the anatomical components in a single image. For the past two decades, X-ray Phase Contrast Imaging (PCI) are constantly being under development because of their superiority for imaging low density objects and its ability to a simultaneous visualization of all tissues. But the extraction of the phase signal is not directly possible, making this information not very often retrieved. The required gold standard instrumentation for PCI is currently a synchrotron facility, limiting clinical applications due to limited access.Several PCI techniques have already been developed and, despite the advances in the literature, they still face many challenges, both instrumental and dosimetric. In this context, the main motivation of this PhD was to propose and develop a phase contrast imaging technique that is easily transferable to conventional sources. The speckle based PCI technique was chosen because, compared to other PCI techniques, it appears to be the most suitable technique for the dose aspects. In addition, it does not require neither an expensive instrumentation nor the specific properties of synchrotron radiation to be implemented. Despite these benefits, it required many algorithmic developments and optimization of the experimental configurations before a transfer on conventional sources.In the first part of the thesis, we propose to show the diagnostic potential of the PCI for osteoarticular applications by imaging anatomical pieces and small animal osteoarticular models. The development and the optimization of speckle based PCI was first performed using the ideal conditions of the European synchrotron source. In particular, a new phase retrieval algorithm has been implemented permitting to reduce the delivered dose while maintaining a constant image quality compared to other speckle based PCI techniques. Several acquisition schemes and experimental conditions were tested. A new instrumental solution for speckle generation has been created. Finally, under these optimized conditions, measurements were made with various conventional X-ray sources. The results obtained have demonstrated the feasibility of the transfer on standard sources under compatible experimental conditions of clinical and pre-clinical imaging routines. This transfer could improve the understanding of the osteoarticular diseases as well as the follow-up of different therapeutic strategies and finally an earlier diagnosis
Kissi, Adelaïde. "Equations aux dérivées partielles et classification non exclusive pour l'analyse d'images échographiques de contraste." Tours, 2006. http://www.theses.fr/2006TOUR3306.
Colorectal carcinoma is a prevalent disease in Europe and United States. Despite of progress in detection, the prognosis of survival is weak : over 50% of patients will survive for five years, with the majority dying within the first two years. More than 30 % of carcinoma spread in liver, from overt micro metastasis, due to specific drainage of blood or to specific liver cells. The particular vascularization of liver by two different systems ( hepatic artery and portal vein) implies some changes in the balance between these two systems during the development of tumour. It is often accepted that for small liver lesions ( below 1 mm), blood supply is provided by portal vein. But, with the growing up of these tumours, an arterial supply is required entailing increase in arterial blood flow. It is therefore essential to depict these blood flow changes to detect and characterize lesions by imaging this specific vascularization. An early detection and a precise quantification of their vascularization would improve the diagnosis. Various methods could be used for this application. One of them is the Doppler sonography that allows the depiction of vascularity but is limited by its lack of sensibility and specifity. The nonlinear imaging, a contrast specific imaging technique, overcomes theses limitations, by the use of ultrasound contrast agents (microbubbles), improving tumours detection and characterization. As they are strictly intravascular, a perfect image of micro as macro vascularization can be made providing a quantitative study of perfusion. Thus, the purpose of my thesis was to quantify the liver arterial perfusion from the analysis of the image enhancement, in power Doppler mode, after an injection of ultrasound contrast agents. The perfusion has been estimated, in a regional basis (often the lesion), to extract physiological parameters in this area with two methods: a fully-automated tracking of lesion in image sequences via a segmentation based on a modification of the well known fuzzy competitive agglomerative clustering coupled with an anisotropic diffusion and a region of interest repositioning with optical flow estimation from structure tensor field. The method has been tested on varied lesions (metastasis, adenoma, focal nodular hyperplasia) and the results show that the assessment of lesion vascularization from our segmentation process can potentially be used for the diagnostic of liver carcinoma
Mathieu, Paul. "Conception d’un agent de contraste nanostructuré pour l’imagerie médicale." Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30083.
During the 90’s, iron oxide nanoparticles (NPs) were considered as good Magnetic Resonance Imaging (MRI) contrast agents (CA). However, in 2010, the production of these NPs was stopped for economic reasons : their production was not profitable enough for the pharmaceutical laboratories. Taking into account the developpement of personnalized medicine, and a growing exigency in the field of diagnostics, the objective of this PhD., grounded on a collaboration between researchers in chemistry and sociology, is to question the relevance of NPs in the arising field of multimodal imaging. In this perspective, have been evaluated, as much the practicability of the synthesis as the interest of the medical field towards multimodal imaging CA. This collaboration takes place between one laboratory of sociology, the Centre d’Etude et de Recherche Travail Organisation Pouvoir, and two chemistry laboratories, the Laboratoire de Chimie de Coordination and the Laboratoire Synthèse et Physico-Chimie de Molécules d’Intérêt Biologique. The collaboration with sociologists allowed us to better understand the challenges of the innovation process of a CA including, in the case of a « nano » CA, the aspect of « risks ». The investigations realized in the medical field provided : (a) a historical approach, to seize the reasons of the underutilization of iron oxide during the early 2000’s, leading to the withdrawal of these products and (b) an oversight of the properties deemed essential by the medical professionals, for a competitive CA. The state of the art of the three most used medical imaging techniques (MRI, Nuclear, and CT-Scan) as well as the developemement of the CA used for these techniques are herein reported. The synthesis of an iron/iron oxide, core/shell nanosystem coated with silica (NPFe@FeOx@SiO2) and its PEGylation are detailed. A complete study of its magnetic properties, and its stability in solution are presented. Lastly, the evaluation of these NPs as a CA for T2 MRI, and cytotoxicity assays on sain and cancerous cells are detailed. The results, corroborates their efficiency in imaging, as well as the absence of toxicity, particularly when the system is PEGylated. Then, this manuscript describes the first assays to obtain a multimodal CA. In a first part, we describe the synthesis of bismuth complexes and the attempts of their incorporation inside the silica shell, in order to create a multimodal CA in MRI and CT-Scan. Then the grafting of a gadolinium complex on the surface of the NPFe@FeOx@SiO2 and NPSiO2 have been carried out and the evaluation of its T1/T2 MRI and cytotoxicity properties are presented. In a last part, the locks towards the developpement of a bimodal CA will be discussed, and faced to the procurement locks of multimodal machines by hospitals in France. Indeed, if the developpement of these multimodal CA in the laboratory is in its golden age, the acquisition of multimodal equipement is uncertain, as the sociology study on the acquisitions and integration processes of PET-MRI in French hospitals has clearly shown. We then conclude on the benefits of the collaboration between chemists and sociologists and on the possibilities and perspectives opened by this work
Biscotti, Anaïs. "Synthèse d'agents de contraste oligosaccharidiques pour l'IRM." Rouen, 2016. http://www.theses.fr/2016ROUES047.
The synthesis of new MRI contrast agents based on cyclodextrins was reported. Seven carboxylates ligands have been introduced on the primary face of the macrocycle to chelate Gd(III). The positive influence of the hydroxyl groups on MRI signal has been proed. An efficient synthetic scale-up was then performed in order to carry out potentiometric studies and in vivo MRI analysis. The MRI study was focused on mice's cardiac zones, and revealed promising results as contrast product. However, the weak stability constant of the metallic complex led to introduce the DOTA ligand, daily used for clinical MRI diagnosis, by monosubstitution of the native β-cyclodextrin or its derivatives in order to determine the contribution of the second coordination sphere of cyclodextrin. The efficiency of these new conjugates was evaluated by comparing with that of a compound having no inner sphere. Relaxemetric studies were performed and proved the influence of the hydroxyl groups on the relaxivity measurements. Nevertheless, the exact effect of the second sphere could not be measured. To improve the influence of the macrocycle on relaxivity values by maintaining the lantanide in the cavity axis, a new synthetic strategy was started to introduce the nitrogen ligand on one primary hydroxyl of both A and D units of α-cyclodextrin
Simonpietri, Caroline. "Techniques modernes en écho Doppler." Paris 5, 1997. http://www.theses.fr/1997PA05P158.
Masson, Jean-Baptiste. "Imagerie de contraste ionique térahertz Physique statistique des plasmons polaritons de surface." Phd thesis, Ecole Polytechnique X, 2007. http://pastel.archives-ouvertes.fr/pastel-00002917.
Abe, Lyu. "Imagerie à haute dynamique : coronographie à contraste de phase et détecteurs spécifiques." Nice, 2002. http://www.theses.fr/2002NICE5733.
The existence of extra-solar planets was confirmed in the years 1990, and it is now challenging for astronomers to be able to directly observe them and determine their physical nature. The required performance in terms of high dynamic range imaging is about several tens of million, which has never been reached yet. In order to attain this goal, I have carried out a global reflection on this high dynamic range imaging theme through coronagraphy and specific detectors. The first part of this document is dedicated to the design of photon counting cameras using 800 by 600 pixels CCD with a frame rate of 100 images per second. These developments come within the scope of ground-based observations, especially for stellar coronagraphy and optical long baseline interferometry where the atmospheric turbulence coherence time is only about a few milliseconds in the visible spectrum. The operation of these cameras on the GI2T/REGAIN interferometer could validate my work through scientific programs for which I present the goals and obtained results. The second part more specifically focuses on coronagraphy with the study and the development of the phase knife coronagraph which ultimate goal is to "null" or reject the light from a distant star, so as to detect a faint orbiting companion. This instrument is theoretically compatible with the direct observation of extra-solar planets in terms of intensity ratio (several tens of million). In order to validate the physical principle of this concept, I have built a monochromatic laboratory prototype of this coronagraph, for which I give the obtained performance and extrapolate on the achromatisation possibilities aiming future ground-based observations
Rey, Marie-Christine. "Imagerie fonctionnelle du foie en échographie après injection de produit de contraste." Bordeaux 2, 1999. http://www.theses.fr/1999BOR23053.
Kriaa, Hana. "Imagerie de dislocations par contraste de canalisation des électrons : théorie et expérience." Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0336.
The Electron Channeling Contrast Imaging (ECCI) is a Scanning Electron Microscope (SEM) technique used to contrast and characterize crystalline defects, such as dislocations. These latter generate, in fact, different contrasts according to the orientation of the incident beam with respect to the crystalline planes {hkl}: bright or black/white on a dark background, black on bright background…Theoretical models, based on dynamical diffraction theory, were first developed to describe the contrasts produced by a perfect crystal. Then, they were extended to the case of an imperfect crystal. Nevertheless, such theoretical models do not propose any detailed calculation and any analytical expression. In this thesis, we develop an original theoretical approach for modelling BSE intensity profiles in a crystal containing dislocations parallel to the surface. In this sense, we propose modelling for different diffraction conditions. Secondly, in order to understand the mechanisms of the formation of dislocation ECC images, we confront our experimental results with the obtained theoretical profiles. Finally, we propose a new approach for understanding the deformation mechanisms of materials near interfaces. This methodology consists in characterizing the areas of interest by ECCI before and after introducing, locally, the plastic deformation by nanoindentation. Here, we focus on the case of a TiAl bases alloy
Kriaa, Hana. "Imagerie de dislocations par contraste de canalisation des électrons : théorie et expérience." Electronic Thesis or Diss., Université de Lorraine, 2018. http://www.theses.fr/2018LORR0336.
The Electron Channeling Contrast Imaging (ECCI) is a Scanning Electron Microscope (SEM) technique used to contrast and characterize crystalline defects, such as dislocations. These latter generate, in fact, different contrasts according to the orientation of the incident beam with respect to the crystalline planes {hkl}: bright or black/white on a dark background, black on bright background…Theoretical models, based on dynamical diffraction theory, were first developed to describe the contrasts produced by a perfect crystal. Then, they were extended to the case of an imperfect crystal. Nevertheless, such theoretical models do not propose any detailed calculation and any analytical expression. In this thesis, we develop an original theoretical approach for modelling BSE intensity profiles in a crystal containing dislocations parallel to the surface. In this sense, we propose modelling for different diffraction conditions. Secondly, in order to understand the mechanisms of the formation of dislocation ECC images, we confront our experimental results with the obtained theoretical profiles. Finally, we propose a new approach for understanding the deformation mechanisms of materials near interfaces. This methodology consists in characterizing the areas of interest by ECCI before and after introducing, locally, the plastic deformation by nanoindentation. Here, we focus on the case of a TiAl bases alloy
Berti, Romain. "Caractérisation d'agents de contraste ultrasonore pour l'imagerie et la thérapie." Paris 6, 2010. http://www.theses.fr/2010PA066711.
Allard, Michèle. "Tolérance neurologique des complexes du gadolinium utilisés en imagerie par résonance magnétique." Bordeaux 2, 1989. http://www.theses.fr/1989BOR25051.
Pouliquen, Daniel. "Conception et évaluation de produits de contraste pour l'IRM du proton." Rennes 1, 1988. http://www.theses.fr/1988REN1B004.
Lewin, Maïté. "Imagerie de l'angiogenèse tumorale." Paris 7, 2001. http://www.theses.fr/2001PA077214.
Le, Marrec Loïc. "Investigation ultrasonore, qualitative et quantitative, d'objets à fort contraste." Aix-Marseille 2, 2004. http://theses.univ-amu.fr.lama.univ-amu.fr/2004AIX22103.pdf.
Taton, Philippe. "Imagerie cellulaire d'un modèle expérimental de microthrombose vasculaire." Bordeaux 2, 1998. http://www.theses.fr/1998BOR2M058.
Gerfault, Laurent. "Imagerie des produits de contraste ultrasonore : simulation et approche de la perfusion myocardique." Lyon, INSA, 2000. http://www.theses.fr/2000ISAL0041.
Like other imaging modalities (MRI or X-Ray), ultrasound scanning has become a contrast imaging modality. It consists in the enhancement of standard ultrasound imaging using an intra-veinously injected ultrasound contrast agent (USCA). Video intensity and Doppler signals of perfused region, reached by the contrast agent, are enhanced. Then, contrast imaging allows a better visualization of perfusion of different organs, and the approach of functional imaging like myocardial perfusion study. In vitro efficiency of USCA has been demonstrated, but its in vivo use has shown a decrease of efficiency. This work studies the interactions between contrast agent and intra-corporal medium, and the influence of measurement method in the aims of understanding this lack of efficiency. The influences of intra-corporal medium actions (pulmonary filtering, dilution of USCA bolus, diffusion of internal gas of USCA micro particles cardiac pressure) and ultrasound waves are inspected to evaluate physical modifications of USCA in in-vivo conditions. The impact of these physical changes on acoustical responses of USCA is then studied. As clinical evaluation is performed on echographic images, simulations of echographic signals are computed. Finally, the feasibility of absolute measurement of blood flow rate is evaluated. A comparison between a newly developed fluid dynamics based model of bolus dilution and acoustical measurements made on a circulating tubular phantom is made. Our conclusions are applied to the study of myocardial perfusion using an isolated pig heart model
Brik, Mohab-Eddine. "Utilisation de nitroxydes comme agent de contraste en imagerie par résonance magnétique nucléaire." Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb37603459v.
Thomas, Lijo. "Imagerie polarimétrique active à large spectre pour l’amélioration du contraste et la microscopie." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLO008/document.
Polarization imaging is a technique which reveals contrasts that do not appear in classical intensity images. It transforms the difference in polarimetric properties of a scene into difference in gray level of an image. This technique has found applications in decamouflaging, remote sensing, microscopy etc. Polarimetric imagers often use polarization modulation devices based on liquid crystal variable retarders (LCVR), which are fast and reliable. However, LCVR control the polarization state of light only at one given nominal wavelength, and performance loss might be observed if imaging is performed at other wavelengths, due to the wavelength dependence of the LCVR. If the light source that illuminates the scene has a broad spectrum, it is thus necessary to insert a narrowband spectral filter in the imaging path. However, spectral filtering significantly decreases the amount of light entering the system and thus the signal-to-noise ratio of polarimetric images.A way to circumvent this issue is to achromatize the polarization modulators. However, this comes at the price of higher complexity and cost, and this may not be needed if the objective is to improve target detection performance by increasing the target/background discriminability (or contrast). In the thesis, we present the investigation of the impact of broadening the spectrum of the light entering the system on the discriminability performance of active polarimetric systems. Through simulations, we show that broadening the bandwidth of the illumination can increase the contrast between two regions, as the increase of light flux compensates for the loss of polarimetric precision. Moreover, we show that taking into account the chromatic characteristics of the components of the imaging system, it is possible to further enhance the contrast. We validate these findings through experiments in active polarimetric imaging configuration, and demonstrate that the spectral bandwidth can be considered as an additional parameter to optimize polarimetric imaging set-ups.We collaborated with an industrial partner (Carl Zeiss, Germany) to implement polarization imaging in optical microscopy. Imaging thin and transparent specimen in microscopy is a challenging task. Staining the sample is a solution but it adds false/spurious details to the image, thus not suitable for live imaging. Recently, differential phase contrast (DPC) imaging by asymmetric illumination is proved to be a desirable choice. This works on the principle that the phase gradient of a transparent specimen can be extracted from two images, illuminated and recorded at complementary angles. Then, DPC is computed as normalized difference between two images. Here the light source is programmable LED array and different pattern of illumination can be generated. This imaging method consumes more time and intermittent flash of light from light source makes sample observation inconvenient for the observer.A practical solution we propose is to install two polarization foils with orthogonal polarization axes below the light source side by side and a polarization sensitive camera which can detect orthogonal eigen polarization states at a time in the existing setup. The polarization foils separate light waves from complementary angles since orthogonally polarized light waves do not interact with each other. The polarized light reaches polarization sensitive camera after passing through transparent sample. The pixels sensitive to horizontal and vertical polarization detect horizontal and vertical polarized light respectively. Then horizontal and vertical polarized light information are separated from the recorded image and reconstructed the missing information using debayering process. Through experiments, we show that polarization based DPC and standard DPC images have similar quality in most cases and the new technique reduces time consumption by half
LANG, DANIEL. "Les agents de contraste utilises en imagerie par resonance magnetique (i. R. M. )." Strasbourg 1, 1992. http://www.theses.fr/1992STR15005.
Ouellet, Mireille, and Mireille Ouellet. "Système optique d'imagerie haut contraste embarqué sur un ballon stratosphérique." Master's thesis, Université Laval, 2019. http://hdl.handle.net/20.500.11794/37114.
Plusieurs projets de télescopes spatiaux ont pour objectif d’étudier des exoplanètes en ayant recours à des techniques d’imagerie directe à haut contraste. Afin d’atteindre une différence de contraste requise entre la lumière de l’étoile et celle réfléchie par l’exoplanète, ses systèmes doivent utiliser un coronographe pour occulter la lumière de l’étoile et corriger en temps réel les erreurs de front d’onde avec des techniques d’optique adaptative. Les aberrations sont détectées par un analyseur de front d’onde, puis une boucle de contrôle envoie une commande qui modifie la surface d’un miroir déformable pour compenser les erreurs de front d’onde. Les performances des systèmes d’optiques adaptatives sont cependant souvent limitées par la présente d’erreurs quasi statiques qui sont causées par la différence de trajet optique entre la caméra de science et le senseur de front d’onde. Un système d’imagerie haut contraste a donc été développé pour démontrer le potentiel d’une technique de contrôle qui permet d’éliminer cette source d’erreur. Cette boucle de contrôle a la particularité d’utiliser un coronographe qui permet d’analyser les erreurs de front d’onde directement à partir de l’image de la caméra de science. Le système optique développé dans le cadre de ce mémoire a été testé en laboratoire et a également été optimisé pour réaliser une démonstration fonctionnelle dans des conditions similaires à l’espace lors d’un vol de ballon dans la stratosphère. Les résultats de vol ont permis de valider la maturité technologique de certaines composantes qui ont le potentiel d’être utilisées pour les prochaines générations de télescopes spatiaux.
Several space telescope projects aim to study exoplanets using high-contrast direct imaging techniques. In order to achieve the required difference in contrast between the light from the star and that reflected by the exoplanet, those systems must use a coronagraph to mask the light of the star and correct in real time wavefront errors with adaptive optics techniques.The aberrations are detected by a wavefront sensor, then a control loop sends a command that modifies the surface of a deformable mirror to compensate for the wavefront errors. However, the performance of adaptive optics systems is often limited by the present quasi-static errors that are caused by the optical path difference between the science camera and the wavefront sensor. A high contrast imaging system has been developed to demonstrate the potential of a control technique which enables the reduction of this kind of error. This control loop has the particularity of using a coronagraph which allows the analyze of the wavefront errors directly from the science camera’s image. The optical system developed within the frameworkof this master’s project has been tested in a laboratory and was also optimized to perform afunctional demonstration in space-like conditions during a balloon flight in the stratosphere.The flight results validated the readiness level of some components that could potentially beused for the next generation of space telescopes.
Several space telescope projects aim to study exoplanets using high-contrast direct imaging techniques. In order to achieve the required difference in contrast between the light from the star and that reflected by the exoplanet, those systems must use a coronagraph to mask the light of the star and correct in real time wavefront errors with adaptive optics techniques.The aberrations are detected by a wavefront sensor, then a control loop sends a command that modifies the surface of a deformable mirror to compensate for the wavefront errors. However, the performance of adaptive optics systems is often limited by the present quasi-static errors that are caused by the optical path difference between the science camera and the wavefront sensor. A high contrast imaging system has been developed to demonstrate the potential of a control technique which enables the reduction of this kind of error. This control loop has the particularity of using a coronagraph which allows the analyze of the wavefront errors directly from the science camera’s image. The optical system developed within the frameworkof this master’s project has been tested in a laboratory and was also optimized to perform afunctional demonstration in space-like conditions during a balloon flight in the stratosphere.The flight results validated the readiness level of some components that could potentially beused for the next generation of space telescopes.
Bolley, Julie. "Elaboration et caractérisation d’agents de contraste IRM pour le ciblage des intégrines αvβ3". Thesis, Paris 13, 2014. http://www.theses.fr/2014PA132012/document.
The molecular imaging of tumor angiogenesis currently represents a major field of research for the diagnostic and the development of new treatment strategy of solid tumors. Endothelial cells from tumor neovessels overexpress the αvβ₃ integrins, which selectively bind to Arg- Gly-Asp (RGD)-containing peptides. The angiogenic process plays a key role during the development of other pathologies like cardiovascular diseases. So, the aim of this project is to design a bimodal contrast agent (MRI and fluorescence) targeting αvβ₃ integrins for early angiogenesis detection. Superpamagnetic iron oxide nanoparticles were surface functionalized with cathecol and bisphosphonate as anchoring agents and bearing carboxylic acid or alkyne functions as terminal end groups. We compared the efficiency of conjugation of three different types of molecules (fluorophores, PEG and RGD peptides) using carbodiimide coupling and click chemistry (Huisgen and thio-yne reactions). The stability of the various nanoplatforms and their uses as MRI contrast agents were evaluated. The affinity towards integrins was evidenced by surface plasmon resonance and solid-phase receptor-binding assay with a radioactive competitor ligand. With the aim to improve MRI properties, nanoparticles differing by their size and shape were synthesized and the magnetic properties were studied. The first in vitro and in vivo experiments were performed. In parallel, a theranostic nanoplatform, with both properties of diagnostic and therapy, has been considered
Renault, Gilles. "Etude de la perfusion en échographie de contraste." Paris 11, 2006. https://pastel.archives-ouvertes.fr/pastel-00603579.
Richert, Michael. "Apport de la polarimétrie en imagerie active : optimisation du contraste polarimétrique et mesure de biréfringence induite par imagerie de Mueller." Toulouse, ISAE, 2009. http://www.theses.fr/2009ESAE0015.
Galicher, Raphaël. "Étude de techniques d'imagerie à haut contraste basées sur la cohérence." Phd thesis, Université Paris-Diderot - Paris VII, 2009. http://tel.archives-ouvertes.fr/tel-00436293.
Le, Borgne Edmond. "Imagerie par resonance magnetique : principes et applications en angiographie, interet de l'agent de contraste." Lille 2, 1994. http://www.theses.fr/1994LIL2T011.
Chauvin, Gaël. "Étude des environnements circumstellaires en imagerie à haut contraste et à haute résolution angulaire." Grenoble 1, 2003. http://www.theses.fr/2003GRE10158.
Ln the context of the search for brown dwarfs and giant planets companions to stars, as well as circumstellar disks, a first part of my work has been devoted to the study ofthe detection capabilities performed by high contrast and high angular resolution instruments. 1 have been, mainly, interested by the instruments, which presently equip the large ground based telescopes, and which are composed of an adaptive optics system and an infTared camera, coupled with a stellar coronagraph. 1 have been particularly involved into the integration and test phases of the Nasmyth Adaptive Optics System NAOS, presently installed at the UT4 telescope of the ESO Very Large Telescope, in Chili. 1 also developed a model to study and to predict the detection capabilities performed by su ch instruments as a function of the detector modes, the instrument characteristics, the observing configurations or the atmospheric conditions. Thinking of the limitations and the optimization of the observing detection performances has been crucial for the second part of my work, dedicated to the search for low mass companions to stars and circumstellar disks. Two types of targets have been found ideal for this study: the young, nearby associations due to their evolutionary status and the stars with planets, indirectly detected by the radial velocity measurements. I present the detection of severa! substellar candidates in the young, nearby associations Beta Pictoris, MBM 12 and Tucana-Horologium, as well as an unprecedented work on the fraction of stellar companions and of brown dwarf companions among these stars. 1 also describe the recent results concerning the discovery of faint companions in the circumstellar environment of stars with planets and 1 present the detection capabilities performed thanks to our deep imaging strategy
Bonaldi, Vincent-Marie. "Tomodensitométrie spiralée et optimisation des protocoles d'injection du contraste iodé intra-veineux : études expérimentales en pathologie humaine." Lyon 1, 1998. http://www.theses.fr/1998LYO1T072.
Aired-Selmani, Leila. "Caractérisations théoriques et expérimentales d'agents de contraste ultrasonore ciblés." Thesis, Tours, 2013. http://www.theses.fr/2013TOUR3301/document.
Since they were introducted, contrast agents have revolutionized the ultrasound imaging. They are composed of tiny gaseous microbubbles and when injected intravenously into the blood, they improve the ultrasound image. Targeted imaging is another application based on the physical characteristics of contrast agents. This approach is based on the ligands incorporation into the microbubbles shell. The microbubble attach to the molecular factors overexpressed by endothelial cells, covering the inner wall of blood vessels. To distinguish these microbubbles from those freely circulating, attached microbubble have to produce an acoustic signal that is sufficiently strong. However, the low microbubbles adhesion induces a decrease of the acoustic signal. To make it possible, it is important to determine the effect of the elastic wall on their acoustic response. This thesis aimed to study the effect of elastic walls on the ultrasonic behavior of targeted microbubbles. First, a theoretical model describing a wall with finite thickness was developed. It has been shown that the scattered echo amplitude by a microbubble near a wall with finite thickness is small in comparison to the echo from a microbubble located in an infinite fluid. Furthermore, and in order to account for the effect of blood vessel wall, the mechanical properties of the wall have been incorporated into the model. The results showed that the resonane frequency of a microbubble near the wall is higher than the resonanace of the same microbubble in an infinite medium. Subsequently, we studied the effect of three types of walls on the microbubble behavior including the wall of OptiCell chamber which is commonly used in ultrasonic experiments. We have shown that microbubbles near the OptiCell wall diffuses a higher echo than those far from the wall when the excitation frequency is above the microbubble resonance frequency. On the other side, we observed that small microbubbles to the presence of the wall. Afterward, we developed a model describing a microbubble attached to the wall. We have shown that the microbubble in direct contact with the wall induces a decrease of the echo amplitude compared to the same bubble in infinite liquid. Moreover, the direct contact of the bubble with the wall generates an increase of the resonance frequency relative to a bubble without direct contact. Finally, an experimental study has shown the advantage of the subharmonic imaging to differentiate attached microbubbles from the free ones
Gardin, Isabelle. "Contraste en imagerie par resonance magnetique nucleaire : optimisation des sequences "retour apres inversion" et "retour a la saturation", influence des agents de contraste paramagnetiques." Toulouse 3, 1986. http://www.theses.fr/1986TOU30031.