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Sivadon, Audrey. "Contributions à l’imagerie passive de la cavitation ultrasonore : formation de voies adaptatives en 3D et extension spatiale de nuages de bulles". Electronic Thesis or Diss., Lyon 1, 2022. http://www.theses.fr/2022LYO10172.
Pełny tekst źródłaPassive imaging relies on beamforming algorithms that require large aperture probes to provide good axial resolutions; however, in 3D passive imaging, the matrix probes currently marketed do not meet this constraint. Moreover, these probes have a large number of elements, which makes their use particularly unwieldy. This thesis work focuses on the study and improvement of passive cavitation imaging by addressing two aspects in particular: (i) the practical and efficient implementation of 3D passive imaging, (ii) the problem of imaging large sources such as cavitation clouds. We have combined the application of sparse methods (to reduce the number of active elements of the probe used) and the transposition from 2D to 3D of adaptive algorithms in the frequency domain. This formalism uses the robust estimation of the inter-spectral density matrix (CSM) and allowed us to implement simply and efficiently different algorithms: Delay-And-Sum (DAS), Robust-Capon-Beamformer and Pisarenko. The efficiency of these algorithms in 3D has been tested in terms of width to half height, contrast and position error, on a point source in simulations and on a point reflector in experiments. Finally, in order to address the reality of cavitation clouds, we have investigated the behavior of these reconstruction methods in the case of extended sources. Our 2D simulations show the evolution of the reconstructed images as a function of the cavitation cloud characteristics. This work provides a concrete solution for a simple implementation of 3D passive imaging as well as answers to the expectations on the localization and characterization of a cavitation cloud
Laloy-Borgna, Gabrielle. "Micro-élastographie : caractérisation mécanique de la cellule par ondes élastiques". Electronic Thesis or Diss., Lyon 1, 2023. http://www.theses.fr/2023LYO10058.
Pełny tekst źródłaDyanmic elastography is an imaging method to measure the elasticity of biological tissues in a non-invasive and quantitative way. Recently, the transposition of the technique to a small scale has been called dynamic micro-elastography and has allowed the first measurements of cellular elasticity by shear waves using an optical microscope. This thesis aims to undetstand the limits of this technique and to develop new micro-elastography methods, to test new wave sources but also potential applications of the technique. In a first step, the dispersion of shear waves was studied on gelatin phantoms. Two distinct regimes of guided elastic waves and shear waves were identified. The high-frequency limit of wave propagation was also explored, establishing the existence of a cutoff frequency which explains the absence of ultrasonic shear imaging. The same approach was then applied to visco-elastic fluids, revealing two cutoff frequencies and revisiting previous studies on rheology and wave propagation in this type of medium. Then, the initial objective being to carry out micro-elastography on single cells and the experiments previously carried out with micro-pipettes presenting certain defects, an original method of cellular micro-elastography was developed. An oscillating microbubble is used as a contactless shear wave source at 15 kHz to perform experiments on blood cells whose diameter is about 15 µm. These are the smallest objects ever explored by elastography. Larger objects, cell clusters of a few tens of thousands of cells have also been studied. Indeed, since ultrasound elastography of these tumour models of about 800 µm in diameter is impossible, optical micro-elastography is a suitable technique. These samples contain magnetic nanoparticles, so a magnetic pulse could be used as a wave source. Previously, proofs of concept on both macroscopic (in ultrasonic elastography) and microscopic (in optical micro-elastography) phantoms were conducted to validate the use of this diffuse field source. Finally, pulse wave measurements were performed on retinal arteries of about 50 µm in diameter using laser Doppler holography acquisitions performed in vivo. The application of monochromatic correlation algorithms allowed the measurement of guided wave velocities, finally revealing the existence of a second pulse wave, an antisymmetric bending wave. This guided wave, much slower than the axisymmetric pulse wave studied so far, was also observed on the carotid artery thanks to ultrafast ultrasound acquisitions
Robert, Jade. "Développement de modalités d'imagerie ultrasonore pour le guidage et le suivi interventionnel du traitement des arythmies cardiaques". Electronic Thesis or Diss., Lyon, 2022. http://www.theses.fr/2022LYSE1005.
Pełny tekst źródłaCardiac arrhythmias remain a major public health issue today. Some types of arrhythmias affect tens of millions of people worldwide, while others are the main cause of sudden cardiac death. In the most severe cases, it is imperative perform a treatment in order to preserve the integrity of the patient. However, interventional methods for guiding and monitoring this treatment are limited, sometimes leading to high recurrence rates, depending on the type of arrhythmia. This thesis focuses on the development of ultrafast ultrasound imaging modalities that can overcome these limitations. These modalities are Electromechanical Wave Imaging and Passive Elastography, and could provide relevant information, until now unavailable in clinic. First, ex-vivo studies on isolated working hearts were conducted to evaluate the potential of Electromechanical Wave Imaging. A blind study demonstrated that it was possible to accurately detect the type of stimulation and the source of contraction in 79% of cases. Then, two in-vivo studies, conducted on porcine model, allowed to study the feasibility of the electromechanical wave imaging on two types of probes, more adapted to an interventional context. Waves that could be associated with cardiac contraction were visualized in both studies. Nevertheless, dynamic visualization of the contraction wave was more complex in an in-vivo context, as it requires subjective interpretation of a trained reader. To address this limitation, a novel method based on time-frequency analysis of ultrasound data was developed to provide a more objective representation of the cardiac contraction, without the need of a trained reader. The method was validated, qualitatively and quantitatively, on ex-vivo data, against the reference method used for Electromechanical Wave Imaging in the literature. By applying the method to the data from the in-vivo studies, it could be demonstrated that the described contraction patterns are similar between two consecutive stimulations with same conditions, and that the contraction source is correctly positioned when the stimulation probe is located in the plane. Notably, the observed contraction area was consistent with the pacing area, when located in the imaging plane, in 81% of the cases, during the study performed with an intracardiac probe. Ex-vivo studies on cardiac samples were performed to evaluate the feasibility of detecting single lesions and thermal injury patterns by Passive Elastography. It was demonstrated on a large number of samples (41 out of n = 51, 80% on two studies) that a local stiffness increase (by a factor of 1.6 to 2.5 on average), of the injured areas, was visible by elastography. The distributions of the detected lesions were consistent, and the dimensions correctly estimated (manually, 1.1 to 2.8 mm error on average), although the lesion areas detected by passive elastography were still approximate. Finally, an in-vivo study on a porcine model demonstrated the feasibility of detecting individual or in-line thermal lesions with this method
Temal, Lynda. "Ontologie de partage de données et d'outils de traitement dans le domaine de la neuroimagerie". Rennes 1, 2008. ftp://ftp.irisa.fr/techreports/theses/2008/temal.pdf.
Pełny tekst źródłaMénard, Laurent. "Étude, développement et évaluation clinique d'un imageur gamma per-operatoire". Versailles-St Quentin en Yvelines, 1999. http://www.theses.fr/1999VERS0002.
Pełny tekst źródłaTaron, Maxime. "Ecalage et modélisation de formes avec incertitudes : contributions et applications à la segmentation avec a priori statistique". Marne-la-vallée, ENPC, 2007. http://www.theses.fr/2007ENPC0734.
Pełny tekst źródłaBlahuta, Samuel. "Etude et optimisation de matériaux scintillateurs pour l'imagerie médicale". Paris 6, 2011. http://www.theses.fr/2011PA066740.
Pełny tekst źródłaMagimel-Pelonnier, Vincent. "Traitement d'images : vers l'extraction automatique de paramètres : application à la cardiologie en médecine nucléaire". Bordeaux 1, 1985. http://www.theses.fr/1985BOR10528.
Pełny tekst źródłaMulé, Sébastien. "Méthodologie pour l’évaluation de la microcirculation en imagerie ultrasonore de contraste". Paris 11, 2008. http://www.theses.fr/2008PA112033.
Pełny tekst źródłaContrast-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
Cottereau, Benoit. "Modèles hiérarchiques en imagerie MEG/EEG : application à la création rapide de cartes rétinotopiques". Paris 11, 2008. http://www.theses.fr/2008PA112042.
Pełny tekst źródłaWhen combined with image reconstruction techniques, magnetoencephalography (MEG) and electroencephalography (EEG) may open new windows for the observation and exploration of time-resolved brain processes at the local--regional spatial scale. The ill-posedness of the associated inverse problem however, necessitates the introduction of image models as regularizing priors. Basic priors -- e. G. Quadratic in the norm of the expected neural currents -- yield images of brain activity that are often too smeared for the satisfactory elucidation of specific neuroscience questions that focus on localization. On the other hand, more sophisticated prior image models -- even though they would theoretically improve the detection of sparse-focal current distributions -- suffer from scalability issues that imped their practical impact. In this PhD work, my primary objective was to reconcile the best of both approaches. I have derived a multiresolution imaging technique which proceeds iteratively to the fit of image models based on the parcellation of the cortical surface. This latter derives from anatomical and functional priors such as the curvature of the cortical manifold, and/or the coregistration to some atlas relevant to the neuroscience investigation. Technically, the multiresolution imaging technique is approached as an empirical model selection procedure optimized according to the least-generalized cross validation (GCV) error principle. Further, the piecewise current model is adequately approached using a compact parametric model based on equivalent current multipoles
Książki na temat "Imagerie passive – Appareils et matériel"
Trajtenberg, Manuel. Economic analysis of product innovation: The case of CT scanners. Cambridge, Mass: Harvard University Press, 1990.
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