Dissertationen zum Thema „Imagerie par flux vectoriel“
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Ling, Hang Jung. „Écoulement intraventriculaire en échocardiographie Doppler avec réseaux de neurones fondés sur la physique“. Electronic Thesis or Diss., Lyon, INSA, 2024. http://www.theses.fr/2024ISAL0087.
Der volle Inhalt der QuelleThe heart, as the central organ of the cardiovascular system, is responsible for pumping blood to all the body’s cells and tissues. Assessing cardiac health is crucial for the early detection and prevention of cardiovascular diseases. Echocardiography, due to its portability and affordability, is commonly used to evaluate the heart’s efficiency during filling (diastolic function) and ejection (systolic function). While systolic function is typically assessed using parameters like the ejection fraction, diastolic function is often measured through mitral valve and annular velocities, which can sometimes result in inconsistent diagnoses. Intraventricular vector flow mapping (iVFM) offers an alternative approach by reconstructing vector blood flow from color Doppler acquisitions. This method allows for the evaluation of intracardiac blood flow patterns and vortex characteristics, providing potentially more accurate quantification of diastolic function. However, iVFM involves time-consuming preprocessing steps, such as left ventricular segmentation and aliasing correction. This thesis introduces deep learning (DL) techniques to automate these processes. First, 3D DL models were developed to achieve temporally consistent left ventricular segmentation. Next, DL-based methods were applied to address aliasing artifacts through segmentation and deep unfolding techniques. Finally, iVFM was performed using physics-informed neural networks (PINNs) and a physics-guided supervised method. The proposed neural network approaches demonstrated performance on par with the original iVFM technique, with the added benefit of the physics-guided method being independent of explicit boundary conditions. These findings underscore the potential application of PINNs in ultrafast color Doppler imaging with the integration of fluid dynamics equations to enhance reconstruction accuracy. Automating the iVFM pipeline with neural networks enhances its reliability, paving the way for clinical applications and the exploration of new flow-based biomarkers
WECKER, DIDIER. „Imagerie de flux par resonance magnetique nucleaire“. Université Louis Pasteur (Strasbourg) (1971-2008), 1989. http://www.theses.fr/1989STR13070.
Der volle Inhalt der QuelleYzet, Thierry. „Débitmétrie hépatique par IRM de flux : validation et application clinique“. Amiens, 2009. http://www.theses.fr/2009AMIED005.
Der volle Inhalt der QuelleFlow measurements using Phase Contrast Magnetic Resonance Imaging was evaluated at the hepatic level for the portal trunk and the proper hepatic artery. After modification of a medical image processing software developed in-situ, this method of flow IRM was validated for healthy subjects and was compared to Doppler examinations. The variabilities of velocities and flow measurements significantly appear weaker and more reproducible using IRM compared to Doppler ultrasound examination. The application of the technique for pathological populations made it possible to confirm commonly known physiological data and thus allow a non-invasive functional exploration in clinical practice during a standard morphological MRI examination. New developments then appear possible: quantification and evolution of the hepatic fibrosis stages or clinical responses to anti-antigenic therapies as possible examples
Yakam, Simen Francis. „Contribution à l'étude de l'écoulement veineux par imagerie de flux R. M. N“. Toulouse, INPT, 1994. http://www.theses.fr/1994INPT107H.
Der volle Inhalt der QuelleLevilly, Sébastien. „Quantification de biomarqueurs hémodynamiques en imagerie cardiovasculaire par résonance magnétique de flux 4D“. Thesis, Ecole centrale de Nantes, 2020. http://www.theses.fr/2020ECDN0007.
Der volle Inhalt der QuelleIn cardiovascular imaging, a biomarker is quantitative information correlated with an existing or growing cardiovascular pathology. Biomarkers are generally obtained by anatomy and blood flow imaging. Recently, the 4D Flow MRI sequence opened new opportunities in measuring the blood flow within a 3D volume along the cardiac cycle. However, this sequence is a compromise between signalto-noise ratio, resolution and acquisition time. Allocated time being limited, velocity measurements are noisy and low resolution. In that context, biomarkers' quantification is challenging. This thesis's purpose is to enhance biomarkers' quantification and particularly for the wall shear stress (WSS). Two strategies have been investigated to reach that objective. A first solution allowing the spatiotemporal filtering of the velocity field has been proposed. It revealed the importance of the wall for the velocity field modelization. A second approach, being the major contribution of this work, focused on the design of a WSS quantification algorithm. This algorithm, named PaLMA, is based on the local modelization of the wall to build a velocity model near a point of interest. The WSS is computed from the velocity model. This algorithm embeds an a posteriori regularization step to improve the WSS quantification. Besides, a blurring model of 4D Flow MRI is used for the first time in the WSS quantification context. Finally, this algorithm has been validated over synthetic datasets, with carotids' complex flows, concerning the signal-to-noise ratio, the resolution, and the segmentation. The performances of PaLMA are superior to a reference solution in that domain, within a clinical routine context
Jeannot, Valérie. „Contribution à l'utilisation de rhodamines pour le ciblage intracellulaire : synthèse de rhodamnes aliphatiques et étude par imagerie de fluorescence“. Perpignan, 1996. http://www.theses.fr/1996PERP0338.
Der volle Inhalt der QuelleLoubeyre, Pierre. „Imagerie des vaisseaux par résonance magnétique : des méthodes sensibles au flux à celles dépendantes de la relaxation sanguine“. Lyon 1, 1996. http://www.theses.fr/1996LYO1T075.
Der volle Inhalt der QuelleCorreia, Mafalda Filipa Rodrigues. „From 2D to 3D cardiovascular ultrafast ultrasound imaging : new insights in shear wave elastography and blood flow imaging“. Thesis, Sorbonne Paris Cité, 2016. http://www.theses.fr/2016USPCC158.
Der volle Inhalt der QuelleThis thesis was focused on the development of novel cardiovascular imaging applications based on 2-D and 3-D ultrafast ultrasound imaging. More specifically, new technical and clinical developments of myocardial shear wave elastography and ultrafast blood flow imaging are presented in this manuscript.At first, myocardial shear wave elastography was developed for transthoracic imaging and improved by a non-linear imaging approach to non-invasively and locally assess shear wave velocity measurements, and consequently tissue stiffness in the context of cardiac imaging. This novel imaging approach (Ultrafast Harmonic Coherent Compounding) was tested and validated in-vitro and the in vivo feasibility was performed in humans for biomechanical evaluation of the cardiac muscle wall, the myocardium. Then, we have translated shear wave elastography to the clinical practice within two clinical trials, each one with a different population (adults and children). In both clinical trials, we have studied the capability of shear wave elastography to assess quantitatively myocardial stiffness in healthy volunteers and in patients suffering from hypertrophic cardiomyopathy. The results in the adult population indicated that shear wave elastography may become an effective imaging tool to assess cardiac muscle stiffness in clinical practice and help the characterization of hypertrophic cardiomyopathy. Likewise, we have also translated Shear Wave Elastography into four-dimensions and we have developed a new approach to map tissue elastic anisotropy in 3-D. 3-D Elastic Tensor Imaging allowed us to estimate quantitatively in a single acquisition the elastic properties of fibrous tissues. This technique was tested and validated in vitro in transverse isotropic models. The in-vivo feasibility of 3D elastic tensor imaging was also assessed in a human skeletal muscle.In parallel, we have developed a novel imaging technique for the non-invasive and non-radiative imaging of coronary circulation using ultrafast Doppler. This approach allowed us to image blood flow of the coronary circulation with high sensitivity. A new adaptive filter based on the singular value decomposition was used to remove the clutter signal of moving tissues. Open-chest swine experiments allowed to evaluate and validate this technique and results have shown that intramural coronary circulation, with diameters up to 100 µm, could be assessed. The in-vivo transthoracic feasibility was also demonstrated in humans in pediatric cardiology.Finally, we have developed a novel imaging modality to map quantitatively the blood flow in 3-D: 3-D ultrafast ultrasound flow imaging. We demonstrated that 3-D ultrafast ultrasound flow imaging can assess non-invasively, user-independently and directly volumetric flow rates in large arteries within a single heartbeat. We have evaluated and validated our technique in vitro in arterial phantoms using a 2-D matrix-array probe and a customized, programmable research 3-D ultrafast ultrasound system, and the in-vivo feasibility was demonstrated in human carotid arteries
Ramona, Mathieu. „Classification automatique de flux radiophoniques par machines à vecteurs de support“. Phd thesis, Paris, Télécom ParisTech, 2010. https://pastel.hal.science/pastel-00529331.
Der volle Inhalt der QuelleWe present here a system for speech/music audio classification, that relies on the excellent statistical properties of Support Vector Machines. This problems raises three questions : how can the SVM, by essence discriminative, be used effeciently on a problem involving more than two classes, how can an audio signal be characterized in a relevant way, and how can the temporel issue be adressed ? We propose a hybrid system for multi-class classification, based on a combination of One-vs-One and dendogram-based approaches, and allowing the estimation of posterior probabilities. The latter are used for the application of post-processing methods that take into account the neighboring frames' inter-dependancies. We thus propose a classification scheme based on the application of Hidden Markov Models on the posterior probabilities, along with an approach based on change detection between segments with "homogeneous" acoustic content. Concerning the audio signal characterization, since it involves a great amount of audio descriptors, we propose new algorithms for feature selection, based on the recent Kernel Alignement criterion. This criterion is also used for the kernel selection step in the classification process. The proposed algorithms are compared to the state-of-the-art, and constitute a relevant alternative in terms of computational cost and storage. The system built from these contributions has been used for a participation to the ESTER 2 evaluation campaign, that we present, along with our results
Ramona, Mathieu. „Classification automatique de flux radiophoniques par Machines à Vecteurs de Support“. Phd thesis, Télécom ParisTech, 2010. http://pastel.archives-ouvertes.fr/pastel-00529331.
Der volle Inhalt der QuelleLefrançois, William. „Développements méthodologiques en imagerie cardiovasculaire par résonance magnétique chez le petit animal“. Thesis, Bordeaux 2, 2011. http://www.theses.fr/2011BOR21833/document.
Der volle Inhalt der QuelleCardiovascular MRI in rodents is a real challenge in terms of spatial and temporal resolution, contrast and experiment times. Though it is accepted that 3D acquisition should be preferred in small animals, 3D acquisition times can be very long. However, they must remain compatible with in vivo experiment times. The aim of this thesis was therefore to develop new fast 3D methods of cardiovascular imaging in small animals at 4.7 and 9.4 T. First, two 4D cardiac MRI methods (3D time resolved) were developed in «black-blood» contrast. The first method is based on a TrueFISP sequence (Fast Imaging with Steady-state Precession). It allowed to make black blood contrast in one hour acquisition time. The second method is based on a FLASH sequence (Fast Low Angle Shot). It uses a bipolar gradient to suppress the blood signal and the contrast was enhanced by using Manganese. Thirty minutes were then enough. Next, a time-of-flight angiography method for the whole body of mice was developed. The vascular contrast was improved by adding preparation modules to suppress the signal from tissues. The imaging of the whole arterial tree was realized within less than ten minutes. Finally, a new 4D time-of-flight method of functional cine angiography with echo-planar acquisition was developed. Preliminary results showed that acquisition times could be divided by four compared with those in classical functional angiography. All these results show that high resolution 3D cardiovascular imaging is possible in reasonable or even fast acquisition times
Salameh, Wassim. „Imagerie par Résonance Magnétique pour la vélocimétrie d’un fluide en milieu poreux“. Thesis, Vandoeuvre-les-Nancy, INPL, 2011. http://www.theses.fr/2011INPL034N/document.
Der volle Inhalt der QuelleThis study presents the development of measurement of porosity and velocity of flow made by MRI in packed beds with glass and polymer beads of various size saturated in water. The advantage of polymer beads is that they do not contain elements ferro or paramagnetics, contrary to the glass beads which disrupt the magnetic field creating artifacts on the MRI images. The calibration of the MRI velocity measurements was achieved from Poiseuille flow in a tube at different flow rates. Two situations were examined: first, the observation of interstitial flows between the beads minimizes partial volume effects and facilitates the correction of the phenomenon of phase aliasing. On the other hand, the measurement of average interstitial velocity (Darcy) requires using simultaneous velocity image and porosity image. In this case, it is preferable to adjust the strength of magnetic field gradient in the velocimetry sequence in a way to avoid any phase aliasing. The geometry of the flow cell was chosen to enable comparison by the MRI method between volume flow rates of water in the porous media and in the outer annulus
Pagé, Gwenaël. „Quantification et caractérisation des écoulements sanguins dans l'arborescence vasculaire de la région cervico-faciale par Imagerie par Résonance Magnétique de flux : évaluation et application“. Thesis, Amiens, 2016. http://www.theses.fr/2016AMIE0041/document.
Der volle Inhalt der QuellePhase-Contrast Magnetic Resonance imaging (PC-MRI) is a non-invasive technique used for quantification and characterization of the blood flow. In clinical pratice, this sequence is principally used in a two-dimensional single slice (2D), but it evolved to a velocity volumic acquisition (4D PC-MRI) allowing a complete quantification of the flow through a vascular tree. However, this technique requires post-processing software which are few and an evaluation of the velocity accuracy in 2D and 4D to quantify vessels with millimetric diameter. In this thesis work, a user-friendly post-processing software of 2D and 4D MRI images has been developed and it is used by research teams and clinicians. MRI acquisitions protocols of velocities for vessels composed by millimetric has been created. These protocols developed in-vitro form a phantom work show an error in the measurement accuracy less than 10%. These validated protocols are applied in facial area arteries in 30 healthy volunteers to create the first hemodynamic data base of arteries in this area. Then, the protocols have been performed to patients with pathologies affecting the facial area to show is interest on patient follow-up and surgical treatment
Alirol, Olivier. „Simulation d'un détecteur CdTe:CI de rayonnement X en mode comptage à fort flux pour la radiothérapie et la tomographie“. Lyon, INSA, 2010. http://theses.insa-lyon.fr/publication/2010ISAL0070/these.pdf.
Der volle Inhalt der QuelleThe use of a semiconductor detector CdTe: Cl for a counting measure of a strong X-photon flux is possible. However, for flows in excess of one hundred million photons per second per square millimeter, we observe a temporal instability in the measures because of the appearance of a space charge in the material. Moreover, this space charge also has an impact on the shape of the 20 image count by changing the curvature of the field lines. The work of this thesis focused on the simulation of the measurement chain, from the Interaction of the photon radiation field X in the semiconductor to the response of the counting electronics. For this, the main obstacle has been the dynamic modeling of space charge and we concentrated our efforts on this particular point. Lt is apparent that the precise knowledge of trap levels in the detector was unthinkable. Soto overcome this difficulty, rather than modeling the electric field , we have measured it by Pockels effect. For this. We developed an experimental bench capable of measuring a dynamic electrical field in a detector during astron X-rays irradiation. Ln addition, we have coupled the measure of field at the counting measure to allow us to connect the two. We validated our simulation of the acquisition of three points: the electric field, the signals due to the interaction of X-rays and measured at the electrodes and the counting response. Thus, our work has resulted in the development and the validation of Iwo tools, useful for understanding the phenomena related to the appearance of a space charge. The first tool is our bench measuring electric field Pockels effect. It allows us to know the amplitude of the field at any point at any moment. And the second tool is our complete simulation of a CdT detector Cl incounting mode with high flows, ranging from the interaction radiation-matter to the response count. We were able to show that space charge is the origin of temporal and spatial instabilities of the measure count
Higazi, Ahmed. „Contribution à l'étude des profils des vitesses des fluides dans les conduites par l'imagerie de flux RMN“. Toulouse 3, 1993. http://www.theses.fr/1993TOU30032.
Der volle Inhalt der QuelleDroulers, Eric. „Flux et flash ou utilisation des séquences rapides en écho de gradient Flash 2D en IRM pour étudier le Flux au niveau des trous déchirés postérieurs et comparaison avec des séquences classiques en écho de spin“. Bordeaux 2, 1990. http://www.theses.fr/1990BOR23059.
Der volle Inhalt der QuelleROTH, MURIEL. „Développements méthodologiques en imagerie d'activation cérébrale chez l'homme par résonance magnétique nucléaire : quantification de flux, imagerie de l'effet BOLD et correction des mouvements de la tête“. Université Joseph Fourier (Grenoble), 1998. http://www.theses.fr/1998GRE10016.
Der volle Inhalt der QuelleLe, Cardinal de Kernier Isaure. „Cytométrie par imagerie grand champ en phase et fluorescence : applications en hématologie“. Thesis, Aix-Marseille, 2019. http://theses.univ-amu.fr.lama.univ-amu.fr/191018_LECARDINALDEKERNIER_341bnro964jhs311fcdqc638rrosk_TH.pdf.
Der volle Inhalt der QuelleBlood cell population analyses allow detecting a wide scope of clinical disorders, ranging from anemias to malaria. A very large number of cells ought to be considered so as to ensure the statistical significance of the result, and in turn, yield a reliable diagnosis. Currently, hematology analyses are based on flow cytometry techniques. High throughput is obtained at the expense of the information content of each acquisition. To reduce the time-to-result, and to minimize the complexity and cost of the systems dedicated to analyzing cell populations, the current need is to reduce the number of acquisitions and optimize the information content. This thesis focuses on single-shot image cytometry as an alternative to flow-based cytometry. It aims at obtaining a set-up based on optical contrasts for the study of large cell populations while preserving the ability to resolve individual cells. We investigate a multi-scale and multi-modal approach to detect, characterize, and classify blood cells. To evaluate the feasibility and clinical relevance of the method, we developed two proof-of-concept set-ups, respectively called the mesoscope and the miniscope. The mesoscope, based on optical developments, combines phase contrast with fluorescence. The complementarity of morphological features and the expression of specific fluorophores enables us to accurately classify blood cells, and for example assess Plasmodium falciparum parasitemia in whole blood samples. The results are benchmarked to reference techniques. However, to address the need for point of care analyses, the system should be miniaturized. Hence, we designed the miniscope, a chip-based bimodal imager
Baptista, Ana Rita. „Permanence du volcanisme sur Mars : caractérisation de la province de Tharsis par imagerie et altimétrie“. Paris, Institut de physique du globe, 2009. http://www.theses.fr/2009GLOB0003.
Der volle Inhalt der QuelleThis work focus in the study of the surface and lithosphere using remote sensing techniques on a telluric planet: the Tharsis Region on Mars. As shown in this work, Olympus Mons and the Tharsis Montes are big topographic highs compensated by deep crustal roots. Moreover, under the also high volcanic Syria Planum, the crust is therefore largely thick. As stated by most of the thermochemical models for the Martian lithosphere the crust is less conductive than the mantle, so impeding a preferential ascension of magma. Consequently, according to our observations, it’s on the present northwestern flank of Olympus Mons, where there’s a passage from a crustal root to a thin crust (with the consequent surface proximity of the mantle) that we observe the highest temperatures. As demonstrated in this work, on Syria Planum, there were detected several particular assembled volcanic features, such as coalesced shield volcanoes in contact with long lobate shape lava flows. These volcanic eruptions may have stopped in the early Hesperian. From then on, on the surface of Syria Planum, there are no evidences for other secondary volcanic manifestations or for surface features related to local heat-increasing, such as those found on Olympus or Tharsis Montes. Furthermore, the thick less conductive crust under Syria may have conditioned the stall of volcanism in that zone. Underneath the Syria crust, the existing melt may have diffused on the lithosphere to the adjacent more conductive mantle, reaching closer the surface. These surfaces are located on the surroundings of the main Tharsis Montes and Olympus Mons
Iosif, Christina. „La compétition de flux comme facteur prédictif de la perméabilité des branches artérielles collatérales après mise en place des stents de diversion de flux dans les artères intracrâniennes“. Thesis, Limoges, 2016. http://www.theses.fr/2016LIMO0002/document.
Der volle Inhalt der QuelleThe outcome of jailing arterial branches that emerge near intracranial aneurysms during flow-diverting stent deployment remains controversial. We report an animal research study aiming to elucidate the role of collateral supply in the hemodynamic changes and neointimal modifications resulting from jailing arteries with flow-diverting stents. To serve this purpose, we sought to quantify the hemodynamic changes at the jailed arterial branches immediately after stenting, as well as quantify the ostia surface values at three months post-stenting, in the presence or absence of collateral arterial flow. Methods After a priori power analysis, two groups (A, B), each containing seven large white swine, were created according to an animal flow model for terminal and anastomotic arterial circulation. Group A corresponded to an arterial configuration with anastomotic type of arterial supply for the territory of the right Ascending Pharyngeal artery (APhA) and group B to an arterial configuration of terminal type of arterial supply for the territory of the right APhA. Subsequently, all animals were stented by flow-diverting stents, jailing the right ascending pharyngeal arteries. Mean flow rates and velocities inside the jailed branches were quantified before and after stenting by time-resolved, 3D, phase contrast MRA. After three months the jailed ostia surface values were quantified on scanning electron microscopic images. The data were analyzed using descriptive statistics and group comparisons with parametric and non-parametric tests.Results Endovascular procedures were feasible, without in situ thrombus formation or ischemic DWI findings on post-procedure MRIs. Immediately following stenting, mean flow rate values at the jailed right ascending pharyngeal arteries were reduced in group A, as compared to the pre-stenting values [P = 0.0008, power: 0.9548]. In contrast, mean flow rates for group B remained similar to the pre-stenting values. At three months post-stenting, mean ostia surface values were significantly higher for group B (527,911 ± 306,229 μm2) than for group A (89,329 ± 59,762 μm2) [P< 0.01, power: 1.00], even though the initial dimensions of the jailed ostia were similar between groups. A statistically significant correlation was found between group (A or B), mean flow rates post-stenting and ostia surface values at three months. ConclusionWhen important collateral supply was present, jailing side arteries with flow-diverters resulted in an immediate, significant reduction in flow rate inside these arteries, as compared to the pre-stenting values. In contrast, when competitive flow was absent, jailing did not result in significant flow rate reductions inside the jailed arteries. Ostium surface values at three months were significantly higher in the terminal group of jailed arteries, compared to the anastomotic group and strongly correlated with the velocity value reductions post- stenting. Key words: flow-diverting stent, collateral arteries, endothelialization, ostium, embolization, magnetic resonance angiography, magnetic resonance imaging
Schuster, Romain. „Développement d'une méthode de mesure basée image pour caractériser en grande taille les flux d'air intérieurs“. Thesis, Rennes 1, 2019. http://www.theses.fr/2019REN1S046/document.
Der volle Inhalt der QuelleWhether for reasons of health and safety at work, thermal comfort or energy saving, it is crucial to study them on site to better control them. The objective of this thesis was to develop a method to measure on site, the speed of indoor air flows over large areas of observation (greater than a square meter). To this end, we turned to image-based techniques that consist in following the movement of passive tracers introduced into the air to infer an estimate of its velocity. This kind of method is already widely used in research laboratories to study flows in well-controlled contexts. However, the transition to on-site measurement and wide field of interest requires some adaptations. These adaptations concern, in particular, the choice of new tracers, the lighting system as well as the motion estimation method from image sequences. First, we developed a motion estimation algorithm that allows the estimation of large-scale velocities from particle images and scalar images. We then tested in our wind tunnel, on mixing layer and cylinder wake flows, a large-scale image-based measurement method using only one camera, a LED lighting system, bubbles or smoke tracers as well as the algorithm mentioned above. We compared the obtained measurement with a measurement carried out by hot-wire anemometry. The results of this measurement campaign showed the ability of the method to measure the main characteristics of the considered flows. Finally, we applied the developed method to an on-site measurement of the suction flow of a laboratory fume hood under real operating conditions. This measure has made it possible to highlight areas of high turbulence and recirculation, causing potential leakages
Bouaou, Kevin. „Apport de la mécanique des fluides dans l'étude des flux sanguins aortiques“. Electronic Thesis or Diss., Sorbonne université, 2020. http://www.theses.fr/2020SORUS076.
Der volle Inhalt der QuelleAging is associated with morphological, functional and hemodynamic changes in the arterial system, most often aggravated by cardiovascular disease. Understanding these aggravating interactions is important to reduce patients risk. Medical imaging plays a major role in this context through modalities such as velocity encoding MRI combined with quantitative image processing and computational resolution of Navier-Stokes equations that govern blood flow hemodynamics. The aim of this thesis is to develop and combine image processing methods dedicated to 4D flow MRI data analysis with computational fluid dynamics to extract quantitative biomarkers such as intra-aortic pressure fields and their spatio-temporal propagations, aortic wall shear stress and intra-aortic vorticity. We have demonstrated the ability of these biomarkers to detect age-related sub-clinical aortic impairment and to characterize pathological aortic dilatation. In addition, association of spatio-temporal aortic pressure distributions with vortex occurrence and duration as well as with wall shear stress were studied. In a second work, we developed a numerical simulation software to solve the Navier-Stokes system using finite element models. An iterative projection method was applied to 2D and 3D vessel stenosis models as well as to 3D geometrical aortic models resulting from segmentation to validate our implementation. Finally, a preliminary work applying our numerical model to patient-specific geometries was performed revealing encouraging associations between simulated data and MRI measures
Gens, Fabrice. „Système ultrasonore d'imagerie et d'estimation du flux sanguin par intercorrélation haute-fréquence : application à l'étude de la microcirculation cutanée“. Tours, 1998. http://www.theses.fr/1998TOUR3302.
Der volle Inhalt der QuelleRima, Samy. „Visuotopie et traitement du flux optique chez le singe : une investigation par IRMf“. Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30330/document.
Der volle Inhalt der QuelleFunctional magnetic resonance imaging (fMRI) allows addressing the functional organization of the human brain with minimal invasiveness and in healthy individuals. The implementation of that technique in non-human primates represents an important achievement in systems neuroscience. On the one hand, monkey fMRI contributes to the reduction and refinement of invasive approaches in non-human primates, by revealing the regions of interest in which focal electrophysiological and/or anatomical investigations should be carried out. On the other hand, the knowledge acquired with such invasive approaches can be more safely transposed to humans, once inter-species homologies and differences have been identified through the use of similar fMRI protocols in human and non-human primates. The first part of this thesis reviews the most common approaches that have been used to study brain functions, either in humans or in non-human primates. It is shown that despite progresses in the human approaches, invasive studies in monkeys remain necessary for understanding the neuronal mechanisms underlying cognitive functions. Then follows a description of the evolution of the monkey fMRI techniques and some of its achievements in bridging the gap between non-invasive human studies and invasive animal studies, notably for deciphering the neural mechanisms supporting visually-guided grasping. The end of this first part is purely methodological. It undertakes the description of the monkey facilities and the MR platform in Toulouse, and details the necessary milestones for conducting fMRI research in macaque monkeys. The second part of the thesis presents the 4 studies we have conducted with monkey fMRI. The first study is a preparatory experiment for characterizing the monkey hemodynamic response function, which is a prerequisite for proper analysis of subsequent monkey fMRI data. The second study addresses the visuotopic organization of the primate dorsal visual cortex with a novel technique of wide-field (80°) phase-encoded visual stimulation, coupled with a state of the art surface-based analysis of population receptive fields. The results obtained in 2 animals uncover a new cluster of visuotopic areas in the posterior parietal cortex of the macaque monkey, bringing a fresh view to the functional organization of this piece of cortex and opening a promising avenue for inter-species comparisons. The third study unveils the cortical network involved in optic flow processing in non-human primates and it compares this network to that recently described in humans. To that end, we replicated in macaque monkeys an experiment previously conducted in human subjects with optic flow stimuli that are either consistent or inconsistent with egomotion. Besides confirming the involvement of areas previously identified through electrophysiological recordings, our results reveal new cortical areas involved in the processing of optic flow, drawing the picture of a network sharing many similarities, but also striking differences, with that documented in the human brain. In summary, the ambition of this thesis is two-fold: (1) providing guidelines for setting-up monkey fMRI techniques, drawn from our own experience and (2) exposing a set of studies we have conducted with this approach, dealing with the visuotopic organization of the dorsal visual cortex and its involvement in the processing of visual motion. Besides bringing a fresh view to the functional organization of the dorsal visual pathway in non-human primates, these studies illustrate how monkey fMRI bridges the gap between electrophysiological studies in non-human primates and functional imaging studies in humans
Lethimonnier, Franck. „Evaluation des cardiopathies ischémiques par IRM quantification du flux et de la réserve coronaire : visualisation des sténoses par angiographie 3D : étude du retentissement fonctionnel par analyse de la fonction ventriculaire gauche“. Angers, 1999. http://www.theses.fr/1999ANGE0508.
Der volle Inhalt der QuelleGarcia, Flores Julio. „Nouvelles approches pour la détermination de la sévérité de la sténose aortique à partir des vitesses du flux sanguin mesurées par imagerie de résonance magnétique“. Thesis, Université Laval, 2012. http://www.theses.ulaval.ca/2012/29190/29190.pdf.
Der volle Inhalt der QuelleAortic valve stenosis is the most common cardiovascular disease after coronary artery diseases and hypertension. Doppler-echocardiography (DE) is the standard method for the evaluation of the severity of aortic stenosis (AS). Valve effective orifice area (EOA) measured by the continuity equation is one of the most frequently used stenotic indices. However, TTE measurement of aortic valve EOA is not feasible or not reliable in a significant proportion of patients. Cardiovascular magnetic resonance (CMR) has emerged as a non-invasive alternative method to evaluate EOA using velocity measurements. The objectives of this thesis were: 1) To compare the DE-derived EOA and CMR-derived EOA using the continuity equation (CE) and 2) To propose new CMR methods to assess EOA and the AS severity; 3) To determine the feasibility of the measurement of the parameters of valve opening and closing kinetics by CMR and 4) To validate new CMR methods to estimate vorticity magnitude. Our work showed a good agreement between the DE-derived EOA and CMR-derived EOA using the CE. This agreement was, however, only due to error compensations. We therefore developed and validated a new CMR method based on the acoustical source term (AST) to estimate the valve EOA and then to introduce a simplified version not requiring vorticity field derivation. This study showed that AST-derived EOA calculated from CMR velocity field measurements is a reliable method to estimate valve EOA and can be useful to confirm AS severity when DE examination is inconclusive. Hence, CMR provides a non-invasive and reliable alternative to DE for the quantification of AS severity. Our work also demonstrated the excellent feasibility and reproducibility of CMR for the measurement of valve kinetic parameters in patients with AS. Furthermore, these parameters compare favorably with conventional indices of stenosis severity to predict risk of poor prognosis. However, the use of CE to estimate EOA may be subject to measurement errors. Furthermore, a validation of new CMR methods for estimate vorticity magnitude was presented. Vorticity and vortical structures play a fundamental role affecting the evaluation of energetic aspects of cardiovascular function. In conclusion, our work demonstrates the feasibility, reliability, and utility of new CMR methods and parameters to identify and quantify the dysfunction of native. New CMR methods estimating vorticity were validated in vivo.
Belmajdoub, Fouad. „Développement d'une méthode de reconstruction 3D du tronc scoliotique par imagerie numérique stéréoscopique et modélisation des calculs par réseaux de Pétri à flux de données en vue d'une implémentation sur une architecture parallèle“. Aix-Marseille 3, 1993. http://www.theses.fr/1993AIX30087.
Der volle Inhalt der QuelleMarsac, Perrine. „Analyse automatisée d’images IRM ciné et flux 4D (3D+t) pour une meilleure quantification des fuites des valves cardiaques chez l’Humain“. Electronic Thesis or Diss., Sorbonne université, 2024. http://www.theses.fr/2024SORUS031.
Der volle Inhalt der QuelleThe heart valves, which enable our heart to behave like a pump alternating flow exchange along with perfect sealing between the different chambers, can be targeted by disease inducing regurgitation, which can at its turn be deleterious to the heart. Regurgitation assessment, currently achieved using echocardiography in clinical routine, can be inaccurate in case of complex or eccentric regurgitant jets. In such cases, patients can be referred to Magnetic Resonance Imaging (MRI) to help for patient management and surgical decision making. Among contributive MRI sequences, 4D flow MRI, which enables visualizing the velocities in the cardiac volume according to the 3 space directions and during the entire cardiac cycle, can help in estimating both straightforward indices such as velocities as well as advanced hemodynamic indices such as pressure gradients. Of note, such 4D flow data are acquired with relevant anatomical cine images within the same exam.This thesis aims to develop dedicated methods to process both 2D and 4D MRI images and extract quantitative indices of mitral regurgitation. In such context, we sought to calculate quantitative MRI indices such as: : 1) the surface and the volume of the regurgitant jet, 2) velocities distribution and the orientation of the main and regurgitant jet to potentially identify the area of flow impact where mechanical stresses might be exerted on the myocardium, 3) a pressure gradients map within the left atrium in the areas surrounding the regurgitant jet, and 4) the temporal persistence of vortices created by the regurgitant jet.These flow data were estimated in conjunction with functional and geometric parameters such as myocardial deformation and atrioventricular angulation, derived from cine MRI images and then compared with echocardiographic measurements as well as with patient exercise capacity
Daviller, Clément. „Quantification de la perfusion myocardique en imagerie de perfusion par résonance magnétique : modèles et classification non-supervisée“. Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1208/document.
Der volle Inhalt der QuelleCardiovascular diseases and in particular coronary heart disease are the main cause of death worldwide with 17.9 million deaths in 2012. Cardiac MRI is a particularly interesting tool for understanding and evaluating heart disease, including ischemic heart disease. Its diagnostic contribution is often major and it provides information that is not accessible by other imaging modalities. The work carried out during this thesis focuses more specifically on the so-called myocardium perfusion test, which consists in studying the distribution of a contrast agent within the heart muscle during its first passage. In clinical practice, this examination is often limited to the clinician's visual analysis, allowing him to identify the culprit artery and deduce the impacted territory. However, this technique is relative and does not quantify myocardial blood flow. In recent years, an increasing number of techniques have emerged to enable this quantification at all stages of processing, from acquisition to the measurement itself. We first established a treatment pipeline to combine these approaches and evaluate them using a digital phantom and clinical data. We demonstrated that the Bayesian approach is able to quantify myocardium perfusion and its superiority in evaluating the arrival time of the indicator bolus compared to the Fermi model. In addition, the Bayesian approach provides additional interesting information such as the probability density function of the measurement and the uncertainty of the residual function, which makes it possible to know the reliability of the measurement carried out, in particular by observing the distribution of the probability density function of the measurement. Finally, we proposed an algorithm for segmentation of myocardial lesions, using the spatial and temporal dimensions of infusion data. This technique allows an objective and precise segmentation of the hypoperfused region allowing a measurement of myocardial blood flow over an area of tissue which behavior is homogeneous and which average signal measurement allows an increase in the contrast-to-noise ratio. In the cohort of 30 patients, the variability of myocardial blood flow measurements performed on voxels detected by this technique was significantly lower than that of measurements performed on voxels in manually defined areas (mean difference=0.14, 95% CI[0.07, 0.2]) and those performed on voxels in areas defined using the bullseye method (mean difference=0.25, 95% CI[0.17, 0.36])
Cornillon, Amandine. „Test de génotypage plaquettaire in vitro à base de sandwich de microparticules biofonctionnalisées : Détection par capteur de fluorescence à ondes évanescentes, imagerie de fluorescence et cytométrie en flux“. Thesis, Ecully, Ecole centrale de Lyon, 2014. http://www.theses.fr/2014ECDL0052/document.
Der volle Inhalt der QuelleThis thesis is about the development of a new assay to capture DNA. This assay is based on the formation of sandwiches between biofunctionnalized with oligonucleotides carboxylatex microparticles combined with fluorescence detection. It should be able to discriminate single nucleotide polymorphism (SNP). This assay is designed to be applied to platelet genotyping for the research of the gene HPA-1. The main goal of this work was to improve an assay previously developed (Trévisan, 2011) by INL and EFS Rhône-Alpes. The objectives are to reduce the number of steps and to simplify the test. To do so, the molecular interactions used in order to capture target DNA are modified and fluorescent microparticles are used for the detection. In the presence of target DNA, sandwiches are formed between both biofunctionnalized fluorescent and magnetic particles. Those sandwiches are purified through magnetic separation. Then, fluorescence is detected by three methods: flow cytometry, fluorescence imaging and Evareader (detection with an evanescent wave). First, chemical and biological parameters for the functionalization of the different particles (magnetic and fluorescent) are determined. The conditions for the capture of target DNA were optimized. Then, the formation and the detection of the sandwiches were estimated by measuring the fluorescence using three different methods: flow cytometry, fluorescence imaging and Evareader. The results obtained with the three methods are consistent. They show that the new system enables to capture synthetic target (oligonucleotide) HPA-1 with a reduction of total time analysis of 45 min. In our conditions, SNP can be discriminated for HPA-1 gene. For this discrimination, the fluorescence signal ratio about 2.5 to 3. This ratio should be improved by optimizing the conditions of sandwiches formation. Next step will consist in the optimization of the system developed to capture DNA in order to gain specificity and to determine the limit of detection. This test should also be validated with biological samples. In the long term, fluorescence could be detected by a miniaturized photodetector developed in the University of Sherbrook. Preliminary studies presented in this manuscript show the potentialities of this new transducer
Cornillon, Amandine. „Test de génotypage plaquettaire in vitro à base de sandwichs de microparticules biofonctionnalisées : détection par capteur de fluorescence à ondes évanescentes, imagerie de fluorescence et cytométrie en flux“. Thèse, Université de Sherbrooke, 2014. http://hdl.handle.net/11143/6024.
Der volle Inhalt der QuelleDarwich, Mohamad Ayham. „Caractérisation locale des propriétés dynamiques artérielles par IRM haute résolution“. Compiègne, 2010. http://www.theses.fr/2010COMP1868.
Der volle Inhalt der QuelleArterial pathologies can often represent serious clinical situations which require an immediate medical examination. Although the modification the structure and the vascular geometry is relatively slow and is carried out during years, the consequences can appear, suddenly, fatal. This work represents a contribution to the methodology of the exploration of the movement of blood, and walls arterial for the characterization of arterial elasticity, and to measure the deterioration of the arterial walls in a noninvasive way. We present two protocols of dynamic imagery based on a bared echo of gradient sequence, with a high temporal resolution (- 5 ms). The relation between MR signal and liquid speed is elucidated via an experimental study, testing the influence of the parameters of imagery and the physical properties of circulation liquid. The reproducibility of MR signal behavior encouraged to propose an estimator based on the speed of blond. Further tests of the feasibility were carried out experimentally and on healthy volunteers, andvelocity results were compared with the technique of phase contrast. The application of the sequence on two close planes made it possible to carry out the second estimator based the speed of pulse wave. A pulsatile hydraulique circuit was implemented, and used to estimate this speed in vitro. The protocol was applied in vivo to estimate the speed of the blood pulse wave of the common carotid, with a distance of 5 cm between the planes. Results of these 2 estimators were experimentally verified, and reproducibility was tested
Perrot, Vincent. „Ultrafast ultrasound imaging for simultaneous extraction of flow and arterial wall motion with linear array probe“. Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1177/document.
Der volle Inhalt der QuelleThis thesis is focused on biomedical engineering for clinical applications. The main goal of this work is to provide to clinicians an ultrasound mode to simultaneously extract wall motion and flow at high frame rates in arteries. Cardiovascular pathologies are a major cause of death and disability worldwide. Although the formation of such diseases is still not fully understood, it appears that some pathological markers from both wall and flow could allow an earlier detection. Because tissues are subject to fast and complex phenomena in the arteries, a high frame rate imaging modality seems highly relevant to extract as much information as possible on the condition of the cardiovascular system. Unfortunately, no technique is currently clinically used or even approved for the extraction of both flow and wall pathological markers at high frame rates. Therefore, in this thesis, I propose to design an ultrasound sequence and algorithm permitting to extract both aspects, at high frame rates on arteries, for a potential clinical application. There are three main scientific contributions in this thesis: i) the design of the ultrasound sequence with a 2D motion estimator, ii) a new adaptive clutter filtering approach, and iii) a clinical trial. The ultrasound sequence is based on plane wave acquisition permitting to yield frame rates up to 10 000 Hz in the carotid. The pipeline used an approach introducing a virtual lateral oscillation in ultrasound images which, coupled with a 2D phase-based estimator based on previous works from the literature, allows to extract vectorial velocity fields. Validations for both flow and wall motion estimation were performed on a commercial Doppler flow phantom and an in-house realistic carotid phantom was designed for the experiments. An adaptive clutter filtering technique was also developed and validated on volunteers based on tissue estimates, which permit to precisely remove tissue clutter from flow signals. Finally, the clinical trial was performed at the hospital with a group of volunteers and a group of patients. The ultrasound sequence, motion estimation algorithm, and adaptive clutter filtering approaches were well validated in the thesis. The method can provide both wall motion and flow estimates at high frame rates, with low errors and standard deviations. The adaptive clutter filtering approach permits to better extract the flow compared to other standard approaches. This improvement is especially noticeable close to the wall, which would allow accurate flow and stress measurements along arterial walls where plaques can form and develop. To conclude, the clinical trial has demonstrated the feasibility in a clinical environment with the extraction of wall motion, flow, and arterial parameters that showed differences between and within groups. This thesis is then a step toward clinical use of high frame rate ultrasound imaging for quantification of both wall motion and flow for pathological detection of cardiovascular diseases
Houriez--Gombaud-Saintonge, Sophia. „Analyse automatisée des données 3D+t d’imagerie par résonance magnétique de vélocimétrie. Quantification de l’apport du 3D+t“. Electronic Thesis or Diss., Sorbonne université, 2020. http://www.theses.fr/2020SORUS328.
Der volle Inhalt der QuelleCardiovascular diseases remain the leading cause of death in OECD countries, in particular, because of the population aging, making it one of the major health issues on a global scale. Advances in imaging today make it possible to better understand and diagnose these diseases in a non-invasive way. More recently, a new non-invasive and non-radiative imaging technique named « 4D Flow MRI » allows for the first time to image the speed of blood flow in three dimensions during a whole cardiac cycle, thus offering new perspectives of visualization, understanding, and measurement. This thesis in image processing carried out in connection with cardiologists and radiologists aims to develop new indicators and to quantify the contribution of 4D flow MRI especially in 1) the assessment of the aortic stiffness leading to a comparison between several approaches to estimate the pulse wave velocity 2) the analysis of flow disorganization in aging and pathological dilation 3) the evaluation of filling flow in the left ventricle
Leblanc, Béatrice. „Etude du débit sanguin cérébral par la méthode du SPECT (Single photon emission Computed Tomography) dans les spasmes infantiles“. Bordeaux 2, 1992. http://www.theses.fr/1992BOR2M116.
Der volle Inhalt der QuelleXavier, Magnier Marie. „Etude quantitative du mouvement de la paroi du coeur à partir d'images ciné-IRM par des méthodes fréquentielles de flux optique“. Thesis, Dijon, 2010. http://www.theses.fr/2010DIJOMU02/document.
Der volle Inhalt der QuelleThe aim of this thesis is to study parietal desynchronisation of the left ventricle from conventional cine-MRI. The first part of our work consisted in the quantification of the left ventricle wall motion of the heart directly from conventional retrospective SSFP type cine-MRI sequences used in the study of cardiac function. The developed methods for measuring displacements within the images are frequency-based optical flow methods. These techniques seem to be particularly adapted to MRI specificities. We have demonstrated their robustness in the event of Rician noise and pixel intensity variations as a function of time. These variations are often associated with the through-plane motion of the heart, in particular in the short-axis orientation. The second part of our work concerned the assessment of desynchronisation from short axis cine-MRI. Time-displacement and time-velocity curves of the heart wall were obtained from tracking points of interest localised on the left ventricle segments close to the endocardium. With respect to the quantification of the delay between curves, our work relied on research carried out in the field of echocardiography desynchronisation. Various parameters for the measurement of desynchronisation from cine-MRI were proposed. This work was the subject of a preliminary clinical study including patients considered as normal further based on clinical examination and patients having normal or prolonged QRS duration without ischemic heart disorder. The dyssynchrony measurements from cardiac MRI were compared to measurements obtained with echocardiography. The first results indicate a good correlation between echography and MRI measurements. The third part of our work consisted in studying heart wall motion directly from raw images from multicoil MRI. The developed optical flow algorithms were tested and they showed that it was possible to estimate myocardial movement. Preliminary results are encouraging. The results of the preliminary study of left intraventricular asynchronism from MRI are also promising. Cardiac cine-MRI could be an alternative to echocardiography in the case of weakly echogenic patients. The validation of this quantitative technique for asynchronism from MRI is of major interest. A more detailed study is in progress, in particular to predict the response of CRT (cardiac resynchronisation therapy) of patients without ischemic disorder presenting a mechanical desynchronisation from MRI and echographic parameters
Garreau, Morgane. „Simulations hémodynamiques pour l'IRM : contrôle qualité, optimisation et intégration à la pratique clinique“. Electronic Thesis or Diss., Université de Montpellier (2022-....), 2023. http://www.theses.fr/2023UMONS040.
Der volle Inhalt der QuelleThe study of hemodynamics, i.e. the dynamics of blood flow, is considered by the medical community as an essential biomarker to characterize the onset and the development of cardiovascular pathologies. Historically, magnetic resonance imaging (MRI), a non-invasive and non-ionizing technique, allows to reconstruct morphological images of the biological tissues. Recent progresses have made it possible to access the temporal evolution of the blood velocity field in the three spatial directions. This technique, known as 4D flow MRI, is still little used in the clinical practice due to its low spatiotemporal resolution and its long scan time.This thesis aims at studying how the 4D flow MRI sequence performs. To begin with, the impact of accelerated sequences (GRAPPA, compressed sensing) on reconstructed velocity fields is studied in a framework combining experimental measurements in a flow phantom and computational fluid dynamics (CFD) simulations. It is shown that the highly accelerated sequence with compressed sensing is in good agreement with numerical simulation as long as appropriate corrections are applied, namely with respect to the eddy currents. Then, the impact of a sequence parameter, namely partial echo, is investigated. The study is conducted thanks to a methodology coupling the simulation of the MR acquisition process with CFD and allowing to reconstruct synthetic MR images (SMRI). This configuration is freed from experimental errors and allows to only focus on the errors intrinsic to the MRI process. Two realistic constructor sequences, without and with partial echo, are simulated for two types of flow in a numerical flow fantom. For both flows, the sequence with partial echo results in overall better results. It suggests that the mitigation of the displacement artifacts made possible by the partial echo has a greater impact than the reduced MR signal acquired that it induces. Furthermore, the coupled MRI-CFD simulation appears as a tool of interest in the context of sequence design and optimization. It could be expanded to other types of MR sequences
Trotier, Aurélien. „Nouvelles stratégies d'acquisitions non cartésiennes pour l'IRM cardiovasculaire du petit animal“. Thesis, Bordeaux, 2015. http://www.theses.fr/2015BORD0255/document.
Der volle Inhalt der QuelleCardiovascular imaging using NMR is still a real challenge. The difficulty relies on the need toacquire images with high temporal and spatial resolutions, in a limited acquisition time and in somecases of moving areas. While most images are acquired with cartesian trajectories, the use of 3D radialtrajectories was explored as an alternative. Indeed, they benefit from various advantages like their lowsensitivity to flow and motion artefacts as well as the opportunity to highly undersample acquisitions.Thus, the aim of this thesis was to develop new acquisition strategies using radial trajectory propertiesfor 3D cardiovascular anatomical and functional imaging in small animals at high magnetic fields.First, a method for measuring blood flow in 3D was developped, based on a time-of-flight effect.The use of radial trajectories allowed to highly reduce acquisition times while increasing spatial andtemporal resolutions compared to cartesian acquisitions.Then, combining the injection of iron nanoparticles which have a long vascular remanence withultrashort echot time radial acquisitions, we showed that anatomical cardiac images with a high spatialresolution could be obtained prospectively or restrospectively by adding a navigator echo in thesequence in order to synchronize the reconstruction to the cardiac cycle.Finally, this method was used to perform 4D flow imaging on the entire cardiopulmonary systemof the animals.The sequences developed during this work and the results obtained in anatomical and functionalimaging show the interest and the robustness of non cartesian methods in preclinical imaging. Theypaves the way to the development of new strategies in clinical imaging.Keywords : Preclinical MRI, 3D+t, radial trajectories, cardiovascular, flow measurement
Fournet, Gabrielle. „IVIM : modeling, experimental validation and application to animal models“. Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS367/document.
Der volle Inhalt der QuelleThis PhD thesis is centered on the study of the IVIM (“Intravoxel Incoherent Motion”) MRI sequence. This sequence allows for the study of the blood microvasculature such as the capillaries, arterioles and venules. To be sensitive only to moving groups of spins, diffusion gradients are added before and after the 180° pulse of a spin echo (SE) sequence. The signal component corresponding to spins diffusing in the tissue can be separated from the one related to spins travelling in the blood vessels which is called the IVIM signal. These two components are weighted by f IVIM which represents the volume fraction of blood inside the tissue. The IVIM signal is usually modelled by a mono-exponential (ME) function and characterized by a pseudo-diffusion coefficient, D*. We propose instead a bi-exponential IVIM model consisting of a slow pool, characterized by F slow and D* slow corresponding to the capillaries as in the ME model, and a fast pool, characterized by F fast and D* fast, related to larger vessels such as medium-size arterioles and venules. This model was validated experimentally and more information was retrieved by comparing the experimental signals to a dictionary of simulated IVIM signals. The influence of the pulse sequence, the repetition time and the diffusion encoding time was also studied. Finally, the IVIM sequence was applied to the study of an animal model of Alzheimer’s disease
Dohet-Eraly, Jérôme. „Méthodes de microscopie par holographie numérique interférentielle en couleurs avec un éclairage partiellement cohérent“. Doctoral thesis, Universite Libre de Bruxelles, 2017. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/250123.
Der volle Inhalt der QuelleThe thesis deals with methods and developments in color digital holographic microscopy (DHM), with a partial spatial coherence illumination. The principal drawback of classical optical microscopy is its poor depth of field, which makes difficult the observation of dynamic phenomena in thick samples. On the contrary, DHM provides reconstruction in depth thanks to numeric propagation of the recorded hologram. Another feature of interferometric DHM is the quantitative phase contrast imaging, useful for analyzing transparent objects. Usual DHM is limited to monochromatic case, but multispectral illumination in an appropriate setup leads to color DHM. Color in-flow imaging of particles in DHM is developed in the thesis, with a method for the automatic correction of color balance and permanent defects. It is applied to analyze plankton microorganisms in untreated pond water samples, and provides high quality images, for both optical phase and intensity. Moreover, noise reduction obtained when decreasing the spatial coherence of the illumination in DHM is also investigated in the thesis, with the development of two models that quantitatively assess the noise reduction as a function of both the spatial coherence of the illumination, and the defocus distance of the noise source. Furthermore, differential DHM (DDHM) is also studied in the thesis. As DHM gives the optical phase, DDHM provides differential phases, from which phase is retrieved by integration. However, misalignments and defects give some aberrations, which affect phase quality and hinder refocusing. A specific hologram processing is developed, giving an accurate phase image and enabling holographic reconstruction in depth. Finally, in DHM, a criterion is essential to automatically achieve the refocusing distance of the object. Two refocusing criteria are developed in the thesis, both working independently of the nature of the observed object (amplitude, phase, or both mixed). The first one, monochromatic, is based on amplitude analysis and on a high-pass filtering process. The second one, which gives fast refocusing in multispectral DHM, compares the phase in the Fourier domain among wavelengths. Methods developed in the thesis show the high potential of color DHM with a partial spatial coherence illumination, suggesting a promising future for this technique.
Doctorat en Sciences de l'ingénieur et technologie
info:eu-repo/semantics/nonPublished
Puiseux, Thomas. „Numerical simulations for phase-contrast magnetic resonance imaging“. Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTS109.
Der volle Inhalt der QuelleHemodynamics (blood flow dynamics) is now recognized as a key marker in the onset and evolution of many cardiovascular disorders such as aneurysms, stenoses, or blood clot formation. As it provides a comprehensive access to blood flows in-vivo, time-resolved 3D phase-contrast magnetic resonance imaging (or 4D Flow MRI) has gained an increasing interest over the last years and stands out as a highly relevant tool for diagnosis, patient follow-up and research in cardiovascular diseases. On top of providing a non-invasive access to the 3D velocity field in-vivo, this technique allows retrospective quantification of velocity-derived hemodynamic biomarkers such as relative pressure or shear stress, which are pertinent for medical diagnosis but difficult to measure in practice. However, several acquisition parameters (spatio-temporal resolution, encoding velocity, imaging artifacts) might limit the expected accuracy of the measurements and potentially lead to erroneous diagnosis. Moreover, the intrinsic complexities of the MRI acquisition process make it generally difficult to localize the sources of measurement errors.This thesis aims at developing a methodology for the assessment of 4D Flow MRI measurements in complex flow configuration. A well-controlled experiment gathering an idealized in-vitro flow phantom generating flow structures typical of that observed in the cardiovascular system is designed. The flow is simultaneously predicted by means of a high-order Computational Fluid Dynamics (CFD) solver and measured with 4D flow MRI. By evaluating the differences between the two modalities, it is first shown that the numerical solution can be considered very close to the ground truth velocity field. The analysis also reveals the typical errors present in 4D flow MRI images, whether relevant to the velocity field itself or to classical derived quantities (relative pressure, wall shear stress). Finally, a 4D Flow MRI simulation framework is developed and coupled with CFD to reconstruct the synthetic MR images of the reference flow that correspond to the acquisition protocol, but exempted from experimental measurement errors. Thanks to this new capability, the sources of the potential errors in 4D Flow MRI (hardware, software, sequence) can be identified
Bresson, Damien. „Étude de l’écoulement sanguin dans un anévrysme intracrânien avant et après traitement par stent flow diverter : quantification par traitement d’images de séquences angiographiques 2D“. Thesis, Compiègne, 2016. http://www.theses.fr/2016COMP2308/document.
Der volle Inhalt der QuelleIntracranial aneurysms treatment based on intra aneurismal flow modification tend to replace traditionally coiling in many cases and not only complex aneurysms for which they were initially designed. Dedicated stents (low porosity, high pores density stents) called “flow diverter” stents are deployed across the neck of the aneurysm to achieve this purpose. The summation of three different mechanisms tend to lead to the healing of the aneurysm: immediate flow alteration due to the mechanical screen effect of the stent, physiological triggering of acute or progressive thrombus formation inside the aneurysm’s pouch and long term biological response leading in neointima formation and arterial wall remodeling. This underlying sequence of processes is also supposed to decrease the recanalization rate. Scientific data supporting the flow alteration theory are numerous and especially computational flow dynamics (CFD). These approaches are very helpful for improving biomechanical knowledge of the relations between blood flow and pathology, but they do not fit in real-time treatments. Neuroendovascular treatments are performed under dynamic x-ray modality (digital subtracted angiography a DSA-).However, in daily practice, FD stents are sized to the patient’s 3D vasculature anatomy and then deployed. The flow modification is then evaluated by the clinician in an intuitive manner: the decision to deploy or not another stent is based solely on a visual estimation. The lack of tools available in the angioroom for quantifying in real time the blood flow hemodynamics should be pointed out. It would make sense to take advantage of functional data contained in contrast bolus propagation and not only anatomical data. Thus, we proposed to create flow software based on angiographic analysis. This software was built using algorithms developed and validated on 2D-DSA sequences obtained in a swine intracranial aneurysm model. This intracranial animal model was also optimized to obtain 3D vascular imaging and experimental hemodynamic data that could be used to realize realistic computational flow dynamic. In a third step, the software tool was used to analyze flow modification from angiographic sequences acquired during unruptured IA from patients treated with a FD stent. Finally, correlation between flow change and aneurysm occlusion at long term follow-up with the objective of identifying predictive markers of long term occlusion was performed
Dhaya, Ibtihel. „Study of the blood-brain interface and glial cells during sepsis-associated encephalopathy : from imaging to histology“. Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0966/document.
Der volle Inhalt der QuelleSepsis-associated encephalopathy (SAE) refers to central nervous system dysfunction during the systemic inflammatory response to infection. In septic patients with encephalopathy MRI has indicated both gray and white matter abnormalities that were associated with worse cognitive outcome including delirium. To improve our understanding of sepsis-associated hemodynamic, metabolic, and structural changes, different MRI sequences were performed in rats that either underwent an i.p injection of saline or bacterial lipopolysaccharide (LPS) 2.5h earlier or cecal ligation and puncture (CLP) 24h earlier. After ip LPS, phase contrast MRI was performed to study anterior and middle cerebral arteries flow and Arterial Spin Labeling (ASL) to study perfusion of white and grey matter brain structures. Diffusion Weighted Imaging (DWI) sequences was used to assess structural changes. After CLP surgery, ASL was used to study microcirculation changes. T2-Weighted Imaging, Diffusion Tensor Imaging (DTI) and tract-based spatial statistics (TBSS) were performed to characterize structural events in different brain structures. After imaging, animals were sacrificed and their brains processed for histology to detect the vasoactive prostaglandin-synthesizing enzyme cyclooxygenase-2 (COX-2) and the astrocytic aquaporin-4 water channel (AQP4) the expression of which can be upregulated during inflammation, to assess the presence of perivascular immunoglobulins (Ig) indicating blood-brain barrier (BBB) leakage and to study glia cell morphology as both microglia and astrocytes are known to change their morphology in inflammatory conditions. Magnetic resonance rat brain imaging indicated no hemodynamic changes in the grey matter after ip LPS administration while an increased CBF was shown in corpus callosum white matter as indicated by ASL. DTI indicated increased water diffusion parallel to fibers of the corpus callosum white matter. These changes were accompanied by BBB breakdown in the white matter and adjacent cortical and striatal grey matter as indicated by the perivascular presence of IgG, but no major changes in vascular COX-2 or white matter glia cell morphology. CLP induced sepsis-associated CNS dysfunction resulted in higher T2-weighted contrast intensities in the cortex, striatum and base of the brain, decreased blood perfusion distribution to the cortex and increased water diffusion in the corpus callosum and ventral striatum compared to sham surgery. These changes were associated in the white matter with modifications in glia cells morphology and in the grey matter with lower expression of constitutive COX-2 expression and AQP4 in the cerebral cortex. The comparison between CLP that underwent or not MRI under isoflurane anesthesia indicated reduced inflammatory response as indicated by COX-2 expression, reduced glia activation and reduced BBB damage in CLP that underwent MRI under isoflurane anesthesia. Collectively, our results suggest that hemodynamic changes may occur in the absence of altered flow in forebrain irrigating arteries. Then, altered white matter structure is an early step in SAE pathogenesis that may result either from BBB breakdown or glial cells activation. This study underlies the deleterious effects of a single exposure to isoflurane anesthesia that may be mitigated by a second exposure in sham-operated rats and the effects of CLP-induced systemic inflammation on glial cells that can be attenuated by imaging under isoflurane anesthesia
Cao, Peng. „Prototypage rapide des artères carotides et étude de l'évolution du vortex au niveau de la bifurcation carotidienne par caméra rapide et IRM“. Phd thesis, Université de Technologie de Compiègne, 2014. http://tel.archives-ouvertes.fr/tel-01062060.
Der volle Inhalt der QuelleCloquet, Christophe. „Optimiser l'utilisation des données en reconstruction TEP: modélisation de résolution dans l'espace image et contribution à l'évaluation de la correction de mouvement“. Doctoral thesis, Universite Libre de Bruxelles, 2011. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209887.
Der volle Inhalt der QuelleLorsque le tableau clinique présenté par un patient n'est pas clair, de nombreuses techniques d'imagerie médicale permettent d'affiner le diagnostic, de préciser le pronostic et de suivre l'évolution des maladies au cours du temps. Ces mêmes techniques sont également utilisées en recherche fondamentale pour faire progresser la connaissance du fonctionnement normal et pathologique du corps humain. Il s'agit par exemple de l'échographie, de l'imagerie par résonance magnétique, de la tomodensitométrie à rayons X ou encore de la tomographie par émission de positrons (TEP).
Certaines de ces techniques mettent en évidence le métabolisme de molécules, comme le glucose et certains acides aminés. C'est le cas de la tomographie par émission de positrons, dans laquelle une petite quantité de molécules marquées avec un élément radioactif est injectée au patient. Ces molécules se concentrent de préférence dans les endroits du corps humain où elles sont utilisées. Instables, les noyaux radioactifs se désintègrent en émettant un anti-électron, encore appelé positron. Chaque positron s'annihile ensuite à proximité du lieu d'émission avec un électron du corps du patient, provoquant l'émission simultanée de deux photons de haute énergie dans deux directions opposées. Après avoir traversé les tissus, ces photons sont captés par un anneau de détecteurs entourant le patient. Sur base de l'ensemble des événements collectés, un algorithme de reconstruction produit enfin une image de la distribution du traceur radioactif.
La tomographie par émission de positrons permet notamment d'évaluer l'efficacité du traitement des tumeurs avant que la taille de celles-ci n'ait changé, ce qui permet d'aider à décider de poursuivre ou non le traitement en cours. En cardiologie, cette technique permet de quantifier la viabilité du muscle cardiaque après un infarctus et aide ainsi à évaluer la pertinence d'une intervention chirurgicale.
Plusieurs facteurs limitent la précision des images TEP. Parmi ceux-ci, on trouve l'effet de volume partiel et le mouvement du coeur.
L'effet de volume partiel mène à des images floues, de la même manière qu'un objectif d'appareil photo incorrectement mis au point produit des photographies floues. Deux possibilités s'offrent aux photographes pour éviter cela :soit améliorer la mise au point de leur objectif, soit retoucher les images après les avoir réalisées ;améliorer la mise au point de l'objectif peut s'effectuer dans l'espace des données (ajouter une lentille correctrice avant l'objectif) ou dans l'espace des images (ajouter une lentille correctrice après l'objectif).
Le mouvement cardiaque provoque également une perte de netteté des images, analogue à l'effet de flou sur une photographie d'une voiture de course réalisée avec un grand temps de pose. Classiquement, on peut augmenter la netteté d'une image en diminuant le temps de pose. Cependant, dans ce cas, moins de photons traversent l'objectif et l'image obtenue est plus bruitée.
On pourrait alors imaginer obtenir de meilleurs images en suivant la voiture au moyen de l'appareil photo.
De cette manière, la voiture serait à la fois nette et peu corrompue par du bruit, car beaucoup de photons pourraient être détectés.
En imagerie TEP, l'effet de volume partiel est dû à de nombreux facteurs dont le fait que le positron ne s'annihile pas exactement à l'endroit de son émission et que le détecteur frappé par un photon n'est pas toujours correctement identifié. La solution passe par une meilleure modélisation de la physique de l'acquisition au cours de la reconstruction, qui, en pratique est complexe et nécessite d'effectuer des approximations.
La perte de netteté due au mouvement du coeur est classiquement traitée en figeant le mouvement dans plusieurs images successives au cours d'un battement cardiaque. Cependant, une telle solution résulte en une diminution du nombre de photons, et donc en une augmentation du bruit dans les images. Tenir compte du mouvement de l'objet pendant la reconstruction TEP permettrait d'augmenter la netteté en gardant un bruit acceptable. On peut également penser à superposer différentes images recalées au moyen du mouvement.
Au cours de ce travail, nous avons étudié des méthodes qui tirent le meilleur parti possible des informations fournies par les événements détectés. Pour ce faire, nous avons choisi de baser nos reconstructions sur une liste d'événements contenant la position exacte des détecteurs et le temps exact d'arrivée des photons, au lieu de l'histogramme classiquement utilisé.
L'amélioration de résolution passe par la connaissance de l'image d'une source ponctuelle radioactive produite par la caméra.
À la suite d'autres travaux, nous avons mesuré cette image et nous l'avons modélisée, pour la première fois, au moyen d'une fonction spatialement variable, non-gaussienne et asymétrique. Nous avons ensuite intégré cette fonction dans un algorithme de reconstruction, dans l'espace image. C'est la seule possibilité pratique dans le cas d'acquisitions en mode liste. Nous avons ensuite comparé les résultats obtenus avec un traitement de l'image après la reconstruction.
Dans le cadre de la correction de mouvement cardiaque, nous avons opté pour l'étude de la reconstruction simultanée de l'image et du déplacement, sans autres informations externes que les données TEP et le signal d'un électrocardiogramme. Nous avons ensuite choisi d'étudier la qualité de ces estimateurs conjoints intensité-déplacement au moyen de leur variance. Nous avons étudié la variance minimale que peut atteindre un estimateur conjoint intensité-mouvement, sur base des données TEP uniquement, au moyen d'un outil appelé borne de Cramer-Rao. Dans ce cadre, nous avons étudié différentes manières existantes d'estimer la borne de Cramer-Rao et nous avons proposé une nouvelle méthode d'estimation de la borne de Cramer-Rao adaptée à des images de grande dimension. Nous avons enfin mis en évidence que la variance de l'algorithme classique OSEM était supérieure à celle prédite par la borne de Cramer-Rao. En ce qui concerne les estimateurs combinés intensité-déplacement, nous avons observé la diminution de la variance minimale possible sur les intensités lorsque le déplacement était paramétrisé sur des fonctions spatiales lisses.
Ce travail est organisé comme suit. Le chapitre théorique commence par brosser brièvement le contexte historique de la tomographie par émission de positrons. Nous avons souhaité insister sur le fait que l'évolution des idées n'est romantique et linéaire qu'à grande échelle. Nous abordons ensuite la description physique de l'acquisition TEP. Dans un deuxième chapitre, nous rappelons quelques éléments de la théorie de l'estimation et de l'approximation et nous traitons des problèmes inverses en général et de la reconstruction TEP en particulier.
La seconde partie aborde le problème du manque de netteté des images et la solution que nous avons choisi d'y apporter :une modélisation dans l'espace image de la réponse impulsionnelle de la caméra, en tenant compte de ses caractéristiques non gaussienne, asymétrique et spatialement variable. Nous présentons également le résultat de la comparaison avec une déconvolution post-reconstruction. Les résultats présentés dans ce chapitre ont fait l'objet d'une publication dans la revue Physics in Medicine and Biology.
Dans un troisième volet, nous abordons la correction de mouvement. Une premier chapitre brosse le contexte de la correction de mouvement en TEP et remet en perspective les différentes méthodes existantes, dans un cadre bayésien unificateur.
Un second chapitre aborde ensuite l'estimation de la qualité des images TEP et étudie en particulier la borne de Cramer-Rao.
Les résultats obtenus sont enfin résumés et replacés dans leur contexte dans une conclusion générale.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
Guo, Jia. „Machine learning in automated analysis of human aorta using innovative 4D flow MRI“. Electronic Thesis or Diss., Sorbonne université, 2023. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2023SORUS591.pdf.
Der volle Inhalt der QuelleThe aorta is the main artery of the human body and plays a key role in the cardiovascular system as it conveys oxygenated blood to our organs while ensuring constant and continuous blood flow and regulated arterial pressures despite the pulsatile and recurrent nature of the heart ejection. This cushioning function of the aorta can however be impaired by various diseases which stiffen the aorta thus reducing its elastic efficiency. This aortic stiffening is often characterized by structural and mechanical changes of the aortic wall interplaying with circulating blood flow disorganization and is known to play a significant role in cardiovascular disease development and progression towards fatal events (aortic wall rupture). Magnetic Resonance Imaging (MRI) is a non-invasive and non-irradiating imaging modality able to provide both aortic anatomy (angiography data) and blood flow dynamics (4D flow data) through volumetric acquisitions. Anatomic angiography data are acquired on a single phase of the cardiac cycle but have a high spatial resolution and contrast. They are usually used in clinical routine to extract morphological indices (diameters on selected slices) and to visualize geometrical malformation (stenosis, dilation, abnormal valves). 4D flow datasets consist in the acquisition of circulating blood flow X, Y and Z velocity components in all aortic voxels during the entire cardiac cycle, but with a lower resolution and overall contrast. In the clinical routine, these data can be visualized but the lack of segmentation tools hinders the extraction of quantitative measures, although they will be of major usefulness for the patient. In our laboratory (Laboratory of Biomedical Imaging, Cardiovascular Imaging team), we have recently developed a semi-automated technique (MIMOSA software) which is able to reliably detect 3D aortic borders on angiographic images. This technique has been applied on the data of 400 patients including: controls with a wide age range (20 to 80 years), patients with aortic dilation, and female patients with abnormally small aorta because of their Turner syndrome (clinical data are made available through our tight collaboration with Pitié-Salpêtrière Hospital). To summarize: 1) there is an urgent need for automated segmentation of the above-mentioned MRI images to accurately quantify aortic morphology, function and well as hemodynamics
Gomez-Balderas, José-Ernesto. „Localisation et commande embarquée d'un drone en utilisant la vision“. Compiègne, 2011. http://www.theses.fr/2011COMP1969.
Der volle Inhalt der QuelleVisual servoing is a control approach based on visual information. In this thesis, visual servoing schemes are proposed to control a quadrotor and an octarotor applied to positioning and navigation task. Concerning the quadrotor we use a hierarchical control scheme whose inner-loop (fast dynamic) focuses on attitude dynamics, while outer-loop (slow dynamics) deals with translational dynamics. Also, a nonlinear controller based on separated saturations for a quadrotor is proposed to stabilize it attitude. The linear position and velocity of the rotorcraft are obtained by using a vision-based algorithm via a monocular caméra. The dynamic model of the quadrotor is presented using the Newton-Euler formalism. In other vision system, two cameras are used to estimate the translational position and velocity of the vehicle. Position was obtained using a frontal camera looking at a target placed on a wall. Quadrotor velocity was estimated using a camera pointing vertically downwards running an optical flow algorithm. Experimental tests showed that the quadrotor performed well at hover flight using the proposed vision based control system. Quadrotor vision-based. The same system was used to estimate the 3D position of the quadrotor over a trajectory using vanishing points. The performance of the vision and control algorithms has been tested in a real application by a quadrotor tracking a line painted in a wall. Similarly the velocity estimation is obtained using an optic flow algorithm. The estimated position and velocity information obtained from the vision system is combined with the angular rates and displacements of the inertial measurement unit to compute the control inputs. It has been shown that the proposed control scheme achieves the tracking objective of the visual reference. Octarotor vision-based. In this thesis, it is presented a visual feedback a control of an octarotor using image-based visual servoing (IBVS) with stereo vision. Autonomous control of an UAV requires a precise measurements and/or estimation of the vehicle’s pose and also the knowledge of its surrounding environment. In order to control the orientation and the position of flying robot with respect to a target, we propose to use a navigation system based on binocular vision system combined with inertial sensors. This combination of sensors, allows us to get a complete characterization of the state of aerial vehicle. In other words, using the stereo vision system we are able to estimate the UAV’s 3D position, while from the inertial sensors we obtain the orientation of rotorcraft. A semi-embedded navigation system combining stereo vision with inertial information is proposed. The hierarchical control approach is appropriate to stabilize the 6DOF dynamics of the quadrotor, it takes advantage of the time scale separation between rotational (fast) and translational (slow) dynamics. For this reason, despite the lower frequency rate of vision-based measurements is able to stabilize in real-time the quadrotor translational dynamics. This combination of measurement strategies has many advantages because one works very well at low speeds (vision system) and the other at high speeds (inertial sensors). Both work at different sample rate. Taking advantage of this property we have obtained a simplified dynamical model of the rotorcraft. This model is given by six independent double integrators which have been stabilized using proportional-derivative (PD) control. The real-time experiments have shown an acceptable performance of the flying machine applying the control law and sensing system proposed. An embedded control system for the mini rotorcraft is implemented. The control is validated by experimental tests. Experimental results show that the implementation of the control law on an embedded control system is satisfactory for autonomous hovering in indoors and outdoors with light or no wind. Real time experiences are developed to validate the performance of navigation systems proposed. This work highlights the potential of the computer vision based position control strategies for UAV
Reynaud, Olivier. „Development of FENSI (Flow Enhanced Signal Intensity) perfusion sequence and application to the characterization of microvascular flow dynamics using MRI“. Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00740639.
Der volle Inhalt der QuelleHoareau, Johan. „Utilisation d'une approche couplée hydrogéophysique pour l'étude des aquifères : application aux contextes de socle et côtier sableux“. Phd thesis, Grenoble 1, 2009. http://www.theses.fr/2009GRE10301.
Der volle Inhalt der QuelleThe pertinence of any aquifer management plan relies o nthe knowledge of this system, and therefore on the information used to chearacterize it. The aim of this thesis is to quantify the improvement of this characterization when geophysical methods are used complementary to hydrogeological techniques. Two hydrogeological contexts have been selected for the study, as their characterization is often difficult while they gather important populations : cristalline hard rock aquifers, and the freshwater lens of sandy coastal aquifers. The results of a numerical study and its validation on two study site located in India reveal that the information brought by electrical resistivity tomography (ERT) and magnetic resonance soundings (MRS) enable to precise the interpretation of pumping tests in hard rock areas. The uncertainly on transmissivity is reduced by an average of 39 % and by an average of 34 % for storativity. In a sandy coastal area, the combined use of water level measurements, Archie's law, time domain electromagnetism (TDEM) and MRS soundings enable to quantify the available freshwater volume. This volume would have been overstimated by 23 % with a more classical approach. Time lapse geophysics also enable to quantify the net recharge of the aquifer for 2008, as 142 mm (for a total rainfall of 2030 mm). As the site present an important geomagnetic field heterogeneity, a new protocol for the acquisition and the interpretation of MRS data has been tested and validated. It is based on the measurements of spin echo signals. It enables to constrain the estimation of water content on this site, which under-estimate by 29 % by the classicla protocol
Ahumada, Daniel F. „Évaluation de la corrélation inter-substitut pour le suivi de tumeurs pulmonaires indirect“. Thesis, 2019. http://hdl.handle.net/1866/24364.
Der volle Inhalt der QuelleThe main objective of this thesis is to prepare the clinical implementation of the Clarity ultrasound system for indirect lung tumours tracking using a surrogate. It is currently used for motion management during prostate treatments and requires adaptation. Our hypothesis is that an internal marker would have a better correlation with the tumour’s position than an external surrogate. The sub-objectives are : 1) test different setups for the image acquisition on patients ; 2) explore the algorithms’ performance for motion detection as well as the image quality metrics on US and dynamic MRI images ; 3) evaluate the correlation between surrogates and a lung structure to determine which performs best. The ultrasound probe is fixed on the treatment couch for the acquisition on healthy volunteers using a mechanical arm. Low pressure on the patient’s skin results in a loss of signal due to the curvilinear shape of the probe. We observed a loss of contact between the probe and the volunteers’ skin due to ample movements causing a deterioration of the image quality. We tested three different motion detection algorithms on dynamic MRI images : normalized cross-correlation (NCC), root mean square error (RMS) and optical flow. The NCC algorithm is the most robust out of the three for 5/9 volunteers for the internal surrogate tracking ( < 0.050). In specific cases, the optical flow method performed better indicating an interest in developping a new algorithm for indirect lung tracking. Finally, the correlation between the surrogates and a lung structure were calculated using the MRI images. The internal surrogate inside the liver was proven more efficient for indirect lung tumour tracking for 8/9 volunteers. External markers give a greater prediction error. It has also been shown that the positioning of the external marker on the patient’s skin impacts the correlation. The abdominal marker is better than the thoracic one for all the volunteers.