Tesi sul tema "Imagerie par Résonnance Magnétique (IRM)"
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Masi, Brice. "Identification de biomarqueurs de l'hépatopathie bilharzienne par imagerie de résonnance magnétique". Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0741/document.
The second parasitic disease in the world behind malaria, bilharzia or schistosomiasis remains a neglected tropical infectious disease. Schistosoma mansoni is the main cause of the digestive form of human schistosomiasis that can progress to a severe chronic pathology in 5 to 10% of infected individuals. Several years after infection, significant hepatic fibrosis develops around parasite eggs in the liver and intestinal wall. Fibrosis can lead to portal hypertension and gastroesophageal varices, the rupture of which is potentially lethal. This hepato-splenic complication of digestive schistosomiasis is often associated with hepatomegaly and splenomegaly. The standard technique for the diagnosis of liver fibrosis is biopsy. The classical non-invasive evaluation of liver fibrosis is done by ultrasound imaging using an international classification scale (Niamey scale). Echography allows the assessment of portal hypertension by measuring the diameter of the portal vein and enables the detection of portal varices. The aim of this work was to provide the first in vivo longitudinal MRI characterization of the murine model of digestive schistosomiasis obtained by infection of CBA/J mice with Schistosoma mansoni. The second objective was to develop a quantitative or semi-quantitative method to evaluate liver fibrosis in this model. Our anatomical and volumetric data show that the murine model of schistosomiasis shares several features with the human disease such as organomegaly, granulomatous inflammation, and portal vein involvement. We propose that T2 mapping could help detect and follow-up semi-quantitatively fibrosis-related schistosomiasis
Deviers, Alexandra. "Imagerie par résonnance magnétique multimodale, en particulier imagerie spectroscopique, du glioblastome : évaluation de facteurs prédictifs de réponse à la radiothérapie". Toulouse 3, 2014. http://www.theses.fr/2014TOU30057.
Glioblastoma (GBM), the most common primary brain tumor in adults, is associated with poor prognosis as local relapse occurs several months after chemo-radiotherapy (RT). New therapeutic strategies are coming to the fore, some of which propose to use imaging biomarkers in order to provide relevant prognostic information or identify pre-RT high relapse risk areas needing to be boosted. The aim of this work was to identify pre-RT MRI markers able to predict relapse location and survival in a cohort of 18 GBM patients included in a phase II clinical trial and treated with RT and Tipifarnib. Data from 3D 1H-Magnetic Resonance Spectroscopic Imaging (3D-MRSI) and diffusion MRI were analysed using a voxel-based spatial comparison of baseline (pre-RT) and relapse images. Three relevant metabolic indices were thus identified: Lactate/N-Acetyl-Aspartate (NAA)> 0. 4; Choline (Cho)/Creatine >1. 63 and Cho/NAA >1. 12. The spatial distribution of these MRSI biomarkers is significantly associated with the site of relapse; furthermore, the magnitude of these metabolic disturbances seems to be correlated with early relapse. These interesting results should be validated in a larger cohort of GBM patients currently included in a prospective phase III clinical trial. The various techniques implemented in this work shall be used in this new study, not only for the evaluation of MRSI and MR diffusion biomarkers, but also for the analysis of perfusion and tensor diffusion imaging
Cassol, Emmanuelle. "Evaluation de l'imagerie par résonnance magnétique de diffusion dans la sclérose en plaques". Toulouse 3, 2004. http://www.theses.fr/2004TOU30024.
Chauffert, Nicolas. "Echantillonnage compressé le long de trajectoires physiquement plausibles en IRM". Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112234/document.
Magnetic Resonance Imaging~(MRI) is a non-invasive and non-ionizing imaging technique that provides images of body tissues, using the contrast sensitivity coming from the magnetic parameters (T$_1$, T$_2$ and proton density). Data are acquired in the $k$-space, corresponding to spatial Fourier frequencies. Because of physical constraints, the displacement in the $k$-space is subject to kinematic constraints. Indeed, magnetic field gradients and their temporal derivative are upper bounded. Hence, the scanning time increases with the image resolution. Decreasing scanning time is crucial to improve patient comfort, decrease exam costs, limit the image distortions~(eg, created by the patient movement), or decrease temporal resolution in functionnal MRI. Reducing scanning time can be addressed by Compressed Sensing~(CS) theory. The latter is a technique that guarantees the perfect recovery of an image from undersampled data in $k$-space, by assuming that the image is sparse in a wavelet basis. Unfortunately, CS theory cannot be directly cast to the MRI setting. The reasons are: i) acquisition~(Fourier) and representation~(wavelets) bases are coherent and ii) sampling schemes obtained using CS theorems are composed of isolated measurements and cannot be realistically implemented by magnetic field gradients: the sampling is usually performed along continuous or more regular curves. However, heuristic application of CS in MRI has provided promising results. In this thesis, we aim to develop theoretical tools to apply CS to MRI and other modalities. On the one hand, we propose a variable density sampling theory to answer the first inpediment. The more the sample contains information, the more it is likely to be drawn. On the other hand, we propose sampling schemes and design sampling trajectories that fulfill acquisition constraints, while traversing the $k$-space with the sampling density advocated by the theory. The second point is complex and is thus addressed step by step. First, we propose continuous sampling schemes based on random walks and on travelling salesman~(TSP) problem. Then, we propose a projection algorithm onto the space of constraints that returns the closest feasible curve of an input curve~(eg, a TSP solution). Finally, we provide an algorithm to project a measure onto a set of measures carried by parameterizations. In particular, if this set is the one carried by admissible curves, the algorithm returns a curve which sampling density is close to the measure to project. This designs an admissible variable density sampler. The reconstruction results obtained in simulations using this strategy outperform existing acquisition trajectories~(spiral, radial) by about 3~dB. They permit to envision a future implementation on a real 7~T scanner soon, notably in the context of high resolution anatomical imaging
Angeletti, Mélodie. "Traitement de données multi-spectrales par calcul intensif et applications chez l'homme en imagerie par résonnance magnétique nucléaire". Thesis, Université Clermont Auvergne (2017-2020), 2019. http://www.theses.fr/2019CLFAC004/document.
As a non-invasive technology for studying brain imaging, functional magnetic resonance imaging (fMRI) has been employed to understand the brain underlying mechanisms of food intake. Using liquid stimuli to fake food intake adds difficulties which are not present in fMRI studies with visual stimuli. This PhD thesis aims to propose a robust method to analyse food stimulated fMRI data. To correct the data from swallowing movements, we have proposed to censure the data uniquely from the measured signal. We have also improved the normalization step of data between subjects to reduce signal loss.The main contribution of this thesis is the implementation of Ward's algorithm without data reduction. Thus, clustering the whole brain in several hours is now feasible. Because Euclidean distance computation is the main part of Ward algorithm, we have developed a cache-aware algorithm to compute the distance between each pair of voxels. Then, we have parallelized this algorithm for three architectures: shared-memory architecture, distributed memory architecture and NVIDIA GPGPU. Once Ward's algorithm has been applied, it is possible to explore multi-scale clustering of data. Several criteria are considered in order to evaluate the quality of clusters. For a given number of clusters, we have proposed to compute connectivity maps between clusters or to compute Pearson correlation coefficient to identify brain regions activated by the stimulation
Chahid, Bochra. "Développement et caractérisation de nouveaux agents de contraste lipidiques ultrasensibles pour l'imagerie par résonnance magnétique destinés à l'imagerie moléculaire". Thesis, Paris 11, 2012. http://www.theses.fr/2012PA114867/document.
The effect of paramagnetic compounds in the chemical shift of endogenous protons, i.e., their resonance frequency, widely used in conventional NMR, can also be a tool to modulate the contrast in magnetic resonance imaging (MRI) by achieving frequency-encoded images depending on the nature or the environment of the entity or tissue to be revealed. This approach involves the transfer of magnetization by chemical exchange of protons also referred to as "Chemical Exchange Saturation Transfer" (CEST). The principle consists in selectively saturate by applying a radio frequency pulse, the signal of labile protons transiently belonging to the structure of the contrast agent or to the water molecules which are associated transiently to it. The image then results from the alteration of the signal of the exchanged protons. The method is based on the actual existence of two sets of protons or pools with two distinct resonance frequencies, one corresponding to the protons associated with the contrast agent and the other represented by the surrounding bulk water.LipoCEST systems, liposomes encapsulating a paramagnetic lanthanide complex, allows such a differentiation of two proton pools constituted on one hand by the water molecules contained in the inner cavity of the liposomes (with a resonance frequency changed by the paramagnetic agent ) and on the other hand by the water present outside the vesicle structure. The sensitivity of such systems is mainly due to the large number of protons in the inner pool. The nature of the paramagnetic agent plays a role in the selectivity of the CEST effect while the nature of the liposome membrane and related permeability behavior controls the proton exchange kinetics between the two water pools. These two parameters must be selected and adjusted to provide effective CEST contrast.The work in this thesis aimed at such a development by optimizing liposome systems for MRI-CEST after intravenous administration. Therefore, the diameter of the liposomes was set below 200 nm and their surface covered by chains of poly (ethylene glycol) to ensure stability in the blood compartment. The choice of chemical shift agents based on lanthanide complexes, mainly thulium-based derivatives, was established from their structural and magnetic properties. The methodology specially developed to encapsulate these entities into vesicles of different membrane composition and permeability to water allowed to generate a new LipoCEST contrast agent
Ozon, Matthew. "Tractographie cardiaque optimale par IRM du tenseur de diffusion". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI020/document.
This thesis "Optimal cardiac tractography using DT-MRI" offers and studies a new formulation of cardiac tractography based on the use of diffusion tensor images that synthetize the information of the diffusion weighted images. The underlying reasons that led to a new formulation are manifold. Existing methods are mostly based on local data, such as the streamlining algorithms, and thus are subject to many imperfections, especially they are not robust to noise in the data. Another problem with this type of approach based on solving differential equations is their dependency on initialization, unlike the method under study. The other aim of this thesis is to determine one or more numerical criteria to compare and qualify fibers. Even though it seems easy to qualitatively characterize fibers based on the visualization, creating measures to characterize the fibers, either in absolute or in comparison to the data or other fibers, is actually challenging
Yang, Feng. "Interpolation des données en imagerie cardiaque par résonance magnétique du tenseur de diffusion". Phd thesis, INSA de Lyon, 2011. http://tel.archives-ouvertes.fr/tel-00578777.
Gros, Hélène. "Mise au point et validation d'un paradigme expérimental en imagerie fonctionnelle événementielle par résonnance magnétique : application au traitement perceptif visuel de stimuli linguistiques". Toulouse 3, 2002. http://www.theses.fr/2002TOU30060.
We propose an experimental design based on a priming paradigm with single visual stimuli to study the role of extrastriate cortex in the perceptual processing of simple linguistic stimuli. We used two sets of stimuli, a linguistic one that consisted of single letters, and a non-linguistic one that consisted of familiar geometric figures; in addition, the ambiguous stimulus "O", which could be categorized either as a letter or as a familiar geometric figure, was primed by both categorical sets. A first study was conducted with an event-related fMRI protocol. The group analysis and the individual analysis on both the extend and intensity of activations showed that the left occipito-temporal cortex was specifically involved in grapheme processing. .
Zhou, Yitian. "Quantification du mouvement et de la déformation cardiaques à partir d'IRM marquée tridimensionnelle sur des données acquises par des imageurs Philips". Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI058/document.
Cardiovascular disease is one of the major causes of death worldwide. A number of heart diseases can be diagnosed through the analysis of cardiac images after quantifying shape and function. However, the application of these deformation quantification algorithms in clinical routine is somewhat held back by the lack of a solid validation. In this thesis, we mainly introduce a fast 3D tagged MR quantification algorithm, as well as a novel pipeline for generating synthetic cardiac US and MR image sequences for validation purposes. The main contributions are described below. First, we proposed a novel 3D extension of the well-known harmonic phase tracking method. The point-wise phase-based optical flow tracking was combined with an anatomical regularization model in order to estimate anatomically coherent myocardial motions. In particular, special efforts were made to ensure a reasonable radial strain estimation by enforcing myocardial incompressibility through the divergence theorem. The proposed HarpAR algorithm was evaluated on both healthy volunteers and patients having different levels of ischemia. On volunteer data, the tracking accuracy was found to be as accurate as the best candidates of a recent benchmark. On patient data, strain dispersion was shown to correlate with the extent of transmural fibrosis. Besides, the ischemic segments were distinguished from healthy ones from the strain curves. Second, we proposed a simulation pipeline for generating realistic synthetic cardiac US, cine and tagged MR sequences from the same virtual subject. Template sequences, a state-of-the-art electro-mechanical (E/M) model and physical simulators were combined in a unified framework for generating image data. In total, we simulated 18 virtual patients (3 healthy, 3 dyssynchrony and 12 ischemia), each with synthetic sequences of 3D cine MR, US and tagged MR. The synthetic images were assessed both qualitatively and quantitatively. They showed realistic image textures similar to real acquisitions. Besides, both the ejection fraction and regional strain values are in agreement with reference values published in the literature. Finally, we showed a preliminary benchmarking study using the synthetic database. We performed a comparison between gHarpAR and another tracking algorithm SparseDemons using the virtual patients. The results showed that SparseDemons outperformed gHarpAR in processing cine MR and US images. Regarding tagged MR, both methods obtained similar accuracies on motion and two strain components (circumferential and longitudinal). However, gHarpAR quantified radial strains more accurately, thanks to the myocardial incompressibility constraint. We conclude that motion quantification solutions can be improved by designing them according to the image characteristics of the modality and that a solid evaluation framework can be a key asset in comparing different algorithmic options
Wei, Hongjiang. "In vivo diffusion tensor imaging (DTI) for the human heart under free-breathing conditions". Thesis, Lyon, INSA, 2013. http://www.theses.fr/2013ISAL0127/document.
The orientation of cardiac fibers underlies the electro-mechanical behavior of the heart, and it is known to be altered in various cardiac diseases such as ischemic heart disease and ventricular hypertrophy. This thesis mainly focuses on in vivo diffusion tensor imaging (DTI) to obtain the myocardial fiber structure of the human heart under free-breathing conditions. The use of DTI for studying the human heart in vivo is challenging due to cardiac motion. In particular, free-breathing DTI acquisition without resorting to respiratory gating is very difficult due to both respiratory and cardiac motion. To deal with this problem, we propose novel approaches that combine multiple shifted trigger delay (TD) acquisitions and post-processing methods. First, we perform multiple shifted TD acquisitions at end diastole. Then, we focus on two different post-processing methods. The first method addresses physiological motion effects on in vivo cardiac DTI using image co-registration and PCATMIP (Principal Components Analysis filtering and Temporal Maximum Intensity Projection). The second method is a wavelet-based image fusion (WIF) algorithm combined with a PCA noise removing method. Finally, a comparison of DTI measurements between the PCATMIP and WIF methods is also performed; tensor fields are calculated, from which the in vivo fiber architecture properties are compared. The results show that using the proposed approaches, we are able to study the cardiac motion effects on diffusion tensor parameters, and investigate the underlying relationship between the measured diffusion tensor properties and the cardiac motion. We also find that the combination of multiple shifted TD acquisitions and dedicated image post-processing can compensate for physiological motion effects, which allows us to obtain 3D fiber architectures of the human heart under free-breathing conditions. The findings suggest new solutions to signal loss problems associated with bulk motion, which are promising for obtaining in vivo human myocardial fiber architecture properties in clinical conditions
Lefebvre, Pauline. "Elastographie par Résonance Magnétique : Nouvelle méthode d’acquisition fondée sur le contrôle optimal et comparaison de l’ERM avec une technique de rhéologie haute-fréquence". Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI116/document.
Magnetic Resonance Elastography is a non-invasive imaging method enabling in vivo characterization of viscoelastic properties of biological tissues. The first part of this thesis deals with the comparison of viscoelastic properties obtained with MRE and with a high-frequency rheometer having a large excitation frequency range. This large frequency range enables common frequency range to MRE, unlike the comparisons usually performed in the literature. To perform MRE measurements, the excitation device and the MRE sequence were developed and an algorithm reconstructing the viscoelastic properties based on an inversion of Helmholtz equation was implemented and evaluated through simulation. The comparison between MRE/rheology was then performed, first on plastisol phantoms with different viscoelastic properties, and then on bovine liver samples. In both cases, results show a very good agreement between values obtained with MRE and those coming from rheology. The second part of this work presents a new acquisition method for MRE. Conventional MRE sequences use oscillating gradients to encode the wave propagation into the phase image. However, these gradients can restrict MRE applications, as their switching frequencies as well as maximal amplitude are limited. The new acquisition strategy we propose in this thesis encodes the wave propagation directly with RF pulses generated with Optimal Control Theory (OCT), in combination with a constant gradient. An initial experiment of phase control with RF pulses is presented, consisting in creating non-trivial spatial phase patterns in MRI phase images, in the absence of wave propagation. Then, RF pulses adapted to the MRE problem are generated with OCT and phase images obtained with these pulses are compared with conventional MRE acquisitions. Viscoelastic properties reconstructed from these two techniques are similar, validating thus this new acquisition method
Li, Hongying. "Fiber tracking and fiber architecture description in cardiac DT-MRI". Thesis, Lyon, INSA, 2013. http://www.theses.fr/2013ISAL0125.
It is important to study the cardiac fiber architecture in order to understand the heart function. Diffusion tensor MRI (DT-MRI) is the only noninvasive technique that allows studying cardiac fiber architecture in vivo. Tractography is essential in representing and visualizing cardiac fiber architecture in DT-MRI, but is often employed qualitatively. The motivation of this thesis is to develop technique for studying the cardiac fiber architecture from the fiber tracts provided by the tractography process in cardiac DT-MRI. Our goal is to develop tractography algorithm and approaches for the quantitative description of cardiac fiber architecture. My work is composed of three main axis. The first is the development of a probabilistic tractography algorithm, which takes fiber spatial correlation into accounts in tracing fibers. Experimental results show that the proposed method is meaningfully more robust to noise than the streamlining method, and produces more regular and smoother fibers, which enables cardiac fiber configurations to be more clearly observed. The second concerns a new framework, namely cardiac fiber unfolding, which is an isometric mapping. Our fiber unfolding framework allows the quantitative description of three dimensional cardiac fiber architecture in a two dimensional plan. Our experimental results show that fiber tract pattern can be observed much easier by unfolding them in a plane, and several cardiac fiber patterns were found. The last axis consists in merging fibers, which is achieved by averaging fibers according to a grid. This fiber merging approach provide simplified fiber architecture at different scale as output that highlights the cardiac fiber configuration
Wang, Lihui. "Modélisation et simulation de l'IRM de diffusion des fibres myocardiques". Phd thesis, INSA de Lyon, 2013. http://tel.archives-ouvertes.fr/tel-00934414.
Sun, Changyu. "Reconstruction et description des fonctions de distribution d'orientation en imagerie de diffusion à haute résolution angulaire". Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0119/document.
This thesis concerns the reconstruction and description of orientation distribution functions (ODFs) in high angular resolution diffusion imaging (HARDI) such as q-ball imaging (QBI). QBI is used to analyze more accurately fiber structures (crossing, bending, fanning, etc.) in a voxel. In this field, the ODF reconstructed from QBI is widely used for resolving complex intravoxel fiber configuration problem. However, until now, the assessment of the characteristics or quality of ODFs remains mainly visual and qualitative, although the use of a few objective quality metrics is also reported that are directly borrowed from classical signal and image processing theory. At the same time, although some metrics such as generalized anisotropy (GA) and generalized fractional anisotropy (GFA) have been proposed for classifying intravoxel fiber configurations, the classification of the latters is still a problem. On the other hand, QBI often needs an important number of acquisitions (usually more than 60 directions) to compute accurately ODFs. So, reducing the quantity of QBI data (i.e. shortening acquisition time) while maintaining ODF quality is a real challenge. In this context, we have addressed the problems of how to reconstruct high-quality ODFs and assess their characteristics. We have proposed a new paradigm allowing describing the characteristics of ODFs more quantitatively. It consists of regarding an ODF as a general three-dimensional (3D) point cloud, projecting a 3D point cloud onto an angle-distance map (ADM), constructing an angle-distance matrix (ADMAT), and calculating morphological characteristics of the ODF such as length ratio, separability and uncertainty. In particular, a new metric, called PEAM (PEAnut Metric), which is based on computing the deviation of ODFs from a single fiber ODF represented by a peanut, was proposed and used to classify intravoxel fiber configurations. Several ODF reconstruction methods have also been compared using the proposed metrics. The results showed that the characteristics of 3D point clouds can be well assessed in a relatively complete and quantitative manner. Concerning the reconstruction of high-quality ODFs with reduced data, we have proposed two methods. The first method is based on interpolation by Delaunay triangulation and imposing constraints in both q-space and spatial space. The second method combines random gradient diffusion direction sampling, compressed sensing, resampling density increasing, and missing diffusion signal recovering. The results showed that the proposed missing diffusion signal recovering approaches enable us to obtain accurate ODFs with relatively fewer number of diffusion signals
Song, Xin. "Path reconstruction in diffusion tensor magnetic resonance imaging". Phd thesis, INSA de Lyon, 2011. http://tel.archives-ouvertes.fr/tel-00694403.
Brzenczek, Cyril. "Modélisation multi-facteurs pour l’aide à la décision dans le traitement par chimiothérapie des tumeurs cérébrales de type gliome diffus de bas grade". Electronic Thesis or Diss., Université de Lorraine, 2021. http://www.theses.fr/2021LORR0095.
Diffuse Low-Grade Glioma (DLGG) is defined by the WHO as a primary tumour of the central nervous system and represents 15% of all glial tumours combined. A DLGG grows slowly, and inevitably evolve into a much more aggressive (grade III) glioma, which eventually leads to the death of the patient. Three types of treatment are available: surgery, chemotherapy and radiotherapy. Today, the median survival rates reported in studies varies from 10 to 15 years. Unfortunately, the prognosis for DLGG is highly variable, with a high standard deviation of total survival, and some patients are surviving only a few years. Within the framework of DLGG management at Nancy University Hospital, chemotherapy is one of the most widely used treatments and there are very variable responses in terms of intensity, duration and response profiles. The thesis work is located in this context. It concerns the study of the response to chemotherapy and consists in developing decision-making tools for the neuro-oncologist in the follow-up of patients. The first part of this thesis work therefore focuses on the choice of the volumetric method. The volume response curve can then be characterised in terms of response intensity. The second part of this work concerns response modelling using statistical learning techniques. Many explanatory variables (epidemiological, genetic) are under study. A new variable called ESVR, which is an original measure allowing us to quantify the infiltrating DLGG phenotype, will also be used. The factorial analysis and machine learning methods initially make possible to define the variables that provide the most information. Exploratory analyses of the data reveal a redundancy of information among certain genetic and epidemiological factors. The models show a greater influence of quantitative variables on the response to chemotherapy compared to qualitative variables. A discussion is finally produced on the importance of the variables used in the prediction of the response to chemotherapy. The aim of this thesis is to produce a set of rules which will enable clinicians to anticipate, before administering the treatment, its effect on tumour volume, which will allow a more advised choice of therapeutic strategy than possible nowadays
Ponchel, Amélie. "Fatigue post-accident vasculaire cérébral : facteurs associés et impact des troubles cognitifs et émotionnels". Thesis, Lille 2, 2016. http://www.theses.fr/2016LIL2S049/document.
Post-stroke fatigue (PSF) is frequent and debilitating. However, PSF is up to date a poorly understood and unrecognized phenomenon. In this thesis, we have done an exhaustive synthesis of scientific literature on factors associated with PSF. It indicates that PSF is frequently related with depressive and anxious symptoms but there is a lack of understanding of its physiopathological mechanisms. We conducted a study of PSF on 153 patients from the hospital-based cohort study STROKDEM (NCT01330160), followed-up for 6 months after an ischemic stroke. In a first study, we have shown that PSF was not a side effect of drugs use. PSF more reflects presence of disturbances frequently observed after stroke such as depression, anxiety, or sleep disturbances. In a second study, we have observed a strong association between PSF and subjective cognitive complaints that contrasted with the absence of association with objective cognitive performances during the neuropsychological evaluation, regardless of the considered cognitive domain. In a third study, we explored neuronal mechanisms underlying PSF. With an exploratory analysis, without a priori, we did not demonstrate any difference in functional connectivity at rest between patients with or without PSF. As a whole, these data give us pieces to progress in the understanding of the complex phenomenon named PSF
Xu, Yanli. "Une mesure de non-stationnarité générale : Application en traitement d'images et du signaux biomédicaux". Thesis, Lyon, INSA, 2013. http://www.theses.fr/2013ISAL0090/document.
The intensity variation is often used in signal or image processing algorithms after being quantified by a measurement method. The method for measuring and quantifying the intensity variation is called a « change measure », which is commonly used in methods for signal change detection, image edge detection, edge-based segmentation models, feature-preserving smoothing, etc. In these methods, the « change measure » plays such an important role that their performances are greatly affected by the result of the measurement of changes. The existing « change measures » may provide inaccurate information on changes, while processing biomedical images or signals, due to the high noise level or the strong randomness of the signals. This leads to various undesirable phenomena in the results of such methods. On the other hand, new medical imaging techniques bring out new data types and require new change measures. How to robustly measure changes in theos tensor-valued data becomes a new problem in image and signal processing. In this context, a « change measure », called the Non-Stationarity Measure (NSM), is improved and extended to become a general and robust « change measure » able to quantify changes existing in multidimensional data of different types, regarding different statistical parameters. A NSM-based change detection method and a NSM-based edge detection method are proposed and respectively applied to detect changes in ECG and EEG signals, and to detect edges in the cardiac diffusion weighted (DW) images. Experimental results show that the NSM-based detection methods can provide more accurate positions of change points and edges and can effectively reduce false detections. A NSM-based geometric active contour (NSM-GAC) model is proposed and applied to segment the ultrasound images of the carotid. Experimental results show that the NSM-GAC model provides better segmentation results with less iterations that comparative methods and can reduce false contours and leakages. Last and more important, a new feature-preserving smoothing approach called « Nonstationarity adaptive filtering (NAF) » is proposed and applied to enhance human cardiac DW images. Experimental results show that the proposed method achieves a better compromise between the smoothness of the homogeneous regions and the preservation of desirable features such as boundaries, thus leading to homogeneously consistent tensor fields and consequently a more reconstruction of the coherent fibers
Wang, Lihui. "Modélisation et simulation de l’IRM de diffusion des fibres myocardiques". Thesis, Lyon, INSA, 2013. http://www.theses.fr/2013ISAL0004/document.
Diffusion magnetic resonance imaging (dMRI) appears currently as the unique imaging modality to investigate noninvasively both ex vivo and in vivo three-dimensional fiber architectures of the human heart. However, it is difficult to know how well the diffusion characteristics calculated from diffusion images reflect the microstructure properties of the myocardium since there is no ground-truth information available and add to that the influence of various factors such as spatial resolution, noise and artifacts, etc. The main objective of this thesis is then to develop realistic model-based dMRI simulators to simulate diffusion-weighted images for both ex vivo and in vivo cardiac fibers by integrating different imaging modalities, and propose a generic tool for the evaluation of imaging quality and image processing algorithms. To achieve this, the present work focuses on four parts. The first part concerns the formulation of basic dMRI simulation theory for diffusion image generation and subsequent applications on simple cardiac fiber models, and tries to elucidate the underlying relationship between the measured diffusion anisotropic properties and the cardiac fiber characteristics, including both physical and structural ones. The second part addresses the simulation of diffusion magnetic resonance images at multiple scales based on the polarized light imaging data of the human heart. Through both qualitative and quantitative comparison between diffusion properties at different simulation scales, the relationship between the microstructure variation and the diffusion properties observed at macroscopic scales is investigated. The third part deals with studying the influence of imaging parameters on diffusion image properties by means of the improved simulation theory. The last part puts the emphasis on the modeling of in vivo cardiac fiber structures and the simulation of the corresponding diffusion images by combining the cardiac fiber structure and the a priori known heart motion. The proposed simulators provide us a generic tool for generating the simulated diffusion images that can be used for evaluating image processing algorithms, optimizing the choice of MRI parameters in both ex vivo and in vivo cardiac fiber imaging, and investigating the relationship between microscopic fiber structure and macroscopic diffusion properties
Huang, Jianping. "Etude de l’imagerie de tenseur de diffusion en utilisant l’acquisition comprimée". Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0136/document.
The investigation of the micro fiber structures of the heart provides a new approach to explaining heart disease and investigating effective therapy means. Diffusion tensor magnetic resonance (DTMR) imaging or diffusion tensor imaging (DTI) currently provides a unique tool to image the three-dimensional (3D) fiber structures of the heart in vivo. However, DTI is known to suffer from long acquisition time, which greatly limits its practical and clinical use. Classical acquisition and reconstruction methods do not allow coping with the problem. The main motivation of this thesis is then to investigae fast imaging techniques by reconstructing high-quality images from highly undersampled data. The methodology adopted is based on the recent theory of compressed sensing (CS). More precisely, we address the use of CS for magnetic resonance imaging (MRI) and cardiac DTI. First, we formulate the magnetic resonance (MR) image reconstruction as a problem of optimization with data-driven tight frame (TF) and total generalized variation (TGV) constraints in the framework of CS, in which the data-driven TF is used to adaptively learn a set of filters from the highly under-sampled data itself to provide a better sparse approximation of images and the TGV is devoted to regularizing adaptively image regions and thus supprressing staircase effects. Second, we propose a new CS method that employs joint sparsity and rank deficiency prior to reconstruct cardiac DTMR images from highly undersampled k-space data. Then, always in the framework of CS theory, we introduce low rank constraint and total variation (TV) regularizations in the CS reconstruction formulation, to reconstruct cardiac DTI images from highly undersampled k-space data. Two TV regularizations are considered: local TV (i.e. classical TV) and nonlocal TV (NLTV). Finally, we propose two randomly perturbed radial undersampling schemes (golden-angle and random angle) and the optimization with low rank constraint and TV regularizations to deal with highly undersampled k-space acquisitons in cardiac DTI, and compare the proposed CS-based DTI with existing radial undersampling strategies such as uniformity-angle, randomly perturbed uniformity-angle, golden-angle, and random angle
Blondiaux, Eléonore. "Détection cellulaire en imagerie cardiaque par résonance magnétique". Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112054.
Objectives: Cardiac regenerative therapies have grown considerably over the past 10 years. Despite positive effects demonstrated in animals, the clinical benefits obtained in humans are still relatively modest. The objective of this work was to better understand the factors associated with implantation of stem cells through the cell detection techniques in magnetic resonance imaging (MRI) and to improve cardiac stem cell therapy in a murine model of myocardial infarction.Materials and methods: A protocol for cell detection with gradient echo T2* sequences in cardiac MRI in vivo and a method for detection of microvessels in cardiac MRI ex vivo with high resolution Susceptibility Weighted Imaging sequences (SWI) were developed and implemented for the study of vectorization of intravenously injected endothelial progenitors cells (EPC) and the integration and evaluation of the impact of mesenchymal stem cells (MSC) administered via cellularized fibrin patches. A permanent ligation of the left anterior coronary artery was performed in adult rats. The stem cells were magnetically labeled with iron oxide nanoparticles by endocytosis.Results: Cell detection imaging showed no cell implantation in the myocardium and no improvement in cardiac functional parameters after intravenous injection of EPC, despite the aid of magnetic vectorization (n = 16 rats). With a local administration of MSC via cardiac patches (n = 37 rats), the left ventricular ejection fraction (LVEF) was improved in cellularized patches groups compared to controls. Microvascular density was increased in the infarcted and peri – infarcted areas in cellularized patches groups compared to controls in immunohistochemistry and in MRI on SWI sequences. The MRI showed no migration of cells into the myocardium from the patch, as confirmed by immunohistochemistry and Perls staining. The persistence of MSCs on the epicardial surface at D21 after implantation and flow cytometry profiling of cytokines and growth factors produced by MSC argue for cell therapy effectiveness related to the secretion of paracrine factors by stem cells.Conclusion: Susceptibility imaging allows: (1) to study myocardial vessels on SWI sequences ex vivo and (2) to assess the implementation of stem cells on gradient echo sequences T2 * in vivo. These techniques have shown that cardiac patches act as a reservoir of soluble mediators which paracrinally target the angiogenesis in the treatment of heart failure in a murine model. This is in favor of a move towards “cell free” biomaterials containing only molecules of interest such as cytokines or growth factors to circumvent immunogenic and teratogenic constraints related to the use of stem cells
Dinet, Bernard. "Anesthésie de l'enfant par Methohexital pour l'examen IRM : [Imagerie par résonance magnétique]". Bordeaux 2, 1990. http://www.theses.fr/1990BOR25253.
Galanaud, Damien. "Exploration des tumeurs cérébrales par IRM multimodalitaire". Aix-Marseille 2, 2004. http://www.theses.fr/2004AIX20688.
121 intracranial tumors of various histologies (gliomas, lymphomas, metastases) were prospectively studied to determine the potential added value of a multimodal NMR approach combining conventional imaging, magnetic resonance spectrometry (MRS) at short (20 ms) and long (135 ms) echo time, diffusion and magnetization transfer imaging for the differential diagnosis of these lesions. In a first step, an univariate analysis of the data was performed to determine the parameters significantly different between groups. These parameters were secondarily used in multivariate analysis, performed using principal component (PCA) and discriminant analysis. PCA using only MRS data clearly separates gliomatosis cerebri and metastases from all other tumor types. Discriminant analysis performed using a combination of MRI and MRS data on strongly enhancing tumors correctly classifies 91% of the lesions as compared to 67% when this study is performed on MRS data only. Discriminant analysis performed on non and moderately contrast enhancing tumors correctly classifies 87% of the lesions as compared to 80% when this study is performed on MRS data only. The information provided by MRS is thus complementary to the one provided by MRI, and the combination of these two modalities has a better diagnostic value than each one taken separately
Chipon, Emilie. "IRM fonctionnelle quantitative appliquée à la vasoréacivité cérébrale". Grenoble 1, 2009. http://www.theses.fr/2009GRE10003.
In neurosciences and medicine, functional imaging of brain perfusion is a mean to characterize regional variations of neuro-vascular coupling and alterations of the vasoreactivity to circulating gases in patients. Arterial Spin Labeling (ASL) is an MRI method which provides a quantitative and reproductible measure of brain perfusion and its dynamical changes, without the need for injection of contrast agents. This thesis presents the implementation of an MRI sequence for the quantification of cerebral blood flow by ASL and its optimization for the study of cerebral vasoreactivity. To obtain a quantitative measure with maximal sensitivity, numerical simulations and experiments on healthy subjects have allowed to optimize: the amplitude of RF pulses, the inversion pulse delays to suppress static signal, the limits of the position of the tagging band with respect to the RF resonator, the minimal allowable gap between tagging band and region of interest, the bolus duration and delay time before acquisition. An original method to rapidly caracterize the bolus of labeled blood in each session has been developed to provide an optimal parametrization of the sequence for each subject. These methods have been used to characterize the effects of inhalation of oxygen and carbogen mixtures with varying CO2 concentrations on perfusion in healthy subjects. In parallel, the same perfusion methods are used in a study to characterize cerebral vasoreactivity in Alzheimer's Disease patients
Didon, Jean-Philippe. "Recalage d'images cérébrales en IRM : application à la pathologie tumorale et vasculaire". Compiègne, 1996. http://www.theses.fr/1996COMPD867.
Germond, Laurence. "Trois principes de coopération pour la segmentation en imagerie de résonnance magnétique cérébrale". Phd thesis, Université Joseph Fourier (Grenoble), 1999. http://tel.archives-ouvertes.fr/tel-00004835.
Madec, Sylvain. "Reconnaissance des lettres : contributions expérimentales en potentiels évoqués et imagerie par résonnance magnétique fonctionnelle". Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4748.
The aim of this thesis is to investigate visual perception processes involved in recognizing letters. Study 1 aims at determining the time window during which letters are discriminated. Our results linking event-related potentials (ERPs) and behavioral measures, indicate effects occurring around 100 ms and 220 ms on right occipital electrodes as reflecting visual processing, while we assume that an effect occurring around 170 ms on fronto-central electrodes might be functionally linked to the retrieval of letter names.Study 2 aims at determining until when, along the process of letter recognition, influences of visual processing are observed. We compare ERPs associated with nominally similar but visually dissimilar letters (by varying the case of presentation), and our results indicate that visual influences are still active until around 300 ms. Study 3 aims at highlighting both the brain areas involved in the retrieval of letter names, as revealed by functional magnetic resonance imaging (fMRI), and the effects induced by this retrieval on ERPs. We use a learning paradigm of unknown visual symbols, in which we induce a gradation in the ability of participants to retrieve the name of these symbols. The gradation is used as a marker of the retrieval of the symbols’ names, both on ERPs and fMRI. We demonstrate that the induced gradation co-varies with ERPs at around 200 ms, and with fMRI signals on left fusiform gyrus and left temporal areas
Baciu, Monica. "Spécialisation hémisphérique de processus cognitifs : évaluation par IRM fonctionnelle". Université Joseph Fourier (Grenoble), 1999. http://www.theses.fr/1999GRE19004.
Petit, Olivia. "Le plaisir et la santé dans la consommation alimentaire : activité cérébrale, motivation et simulation sensorielle". Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM1036/document.
Self-regulation is an essential resource for not succumbing to (junk) food. It requires willpower and control of emotions and sensations. However, individuals operate in an environment enhancing food pleasure where health informations are few and poorly considered, causing difficulties in self-regulation. These difficulties are found especially in overweight people and/or dieter. We hypothesized that value the taste of healthy foods could help people to self-regulate and we conducted two experiments to test it. In the first study, messages highlighting the pleasure of eating fruits and vegetables are more persuasive to subjects taking risks to health. Similarly, in the second study in decision making, focusing on the tatste of these foods increases more healthy food choices for these subjects. By using neuroimaging, we have shown brain activity distinctions between these subjects when choosing healthy food in this condition. Choosing healthy food is more impulsive for the most sensitive to reward subjects, approaching the choice of junk foods. Instead, it appears more reflective for subjects with a high BMI and choosing more junk foods, facilitating self-regulation. At the theoretical level this research highlights the positive role of emotions and sensations related to pleasure in self-regulation. At the managerial level, it suggests the importance of adapting strategies to the target audience in order to efficiently healthy food consumption
Watrin-Pinzano, Astrid. "Influence des composés matriciels sur le signal IRM du cartilage". Nancy 1, 2001. http://www.theses.fr/2001NAN11318.
Fall, Sidy. "Apport de l'analyse spectrale du signal BOLD à l'étude de la connectivité fonctionnelle en imagerie par résonnance magnétique". Amiens, 2007. http://www.theses.fr/2007AMIED012.
Bivariate spectral analysis of fMRI (functional Magnetic Resonance Imaging) time-series that we have developed and which has allowed us to investigate the brain functional connectivity. Conversely to standard temporal methods, the study of covariance structure between signals, within the frequency domain, can permit to overcome regional differences in the physiological noise, intra and inter subject variability of BOLD (Blood Oxygen Level Dependant) response. With a non parametric estimation of the cross-spectral density function, we have estimated spectral parameters of phase and coherence between BOLD signals (regions). Confidence limits associated to these parameters have also been estimated. The interactivity between two regions was accessed through coherence and a topological distance (functional distance). Partial coherence has been also investigated to study a possible effect of modulation induced by a third region over two functionally connected regions and engaged in the task. We have applied this method of functional connectivity to specific circuits of three motor regions. A preparation and execution motor task has been performed. The main results of this study showed that the BOLD signal in the pre-supplementary motor area (pre-SMA) leads both the SMA-proper and the primary motor cortex (M1) during the preparation period. During this period, the strength of interaction between the coupling pre-SMA/M1 was significantly higher than the strength of interaction between the coupling SMA-proper/M1. Inversely, during the execution period of the task, the strength of interaction between the coupling SMA-proper/M1 was significantly higher than the strength of interaction between the coupling pre-SMA/M1. The analysis of the partial coherence has showed a significant common influence of the superior frontal gyrus on the relationship between pre-SMA and M1 regions during the preparation period. Spectral analysis with fMRI data has been successfully used to investigate the functional connectivity in the human brain
Yzet, Thierry. "Débitmétrie hépatique par IRM de flux : validation et application clinique". Amiens, 2009. http://www.theses.fr/2009AMIED005.
Flow 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
Mesrob, Lilia. "Etude IRM individuelle et multimodale dans la maladie d'Alzheimer". Paris 6, 2009. http://www.theses.fr/2009PA066770.
Guay-Bégin, Andrée-Anne. "Nanomatériaux à base d'oxyde de gadolinium - applications en imagerie par résonance magnétique (IRM)". Thesis, Université Laval, 2011. http://www.theses.ulaval.ca/2011/28561/28561.pdf.
Magnetic resonance imaging (MRI) is widely used in medicine to achieve high resolution, in-depth anatomical images. MRI can also be used to detect cells injected in vivo and to track their migration. For this purpose, the cells cannot be clearly visualized in MRI without the use of contrast agents. Gadolinium (III) complexes are by far the most widely used contrast agents in clinical medicine because they provide a drastic enhancement of MRI signal in vascularized tissues. However, the vast majority of these chelates is poorly uptaken and retained into cells. In order to efficiently label cells, gadolinium oxide nanoparticles (Gd2O3) have been recently developed. Therefore, these particles, covered with diethylene glycol (DEG-Gd2O3), were used in the first part of this project to label cells. DEG-Gd2O3-labeled cells can be visualized in MRI, in vitro and in vivo (using the chicken embryo model). However, DEG-Gd2O3 particles aggregate in aqueous saline solution (cell culture medium) and at high concentration, they can impact on the cell proliferation. Molecules such as polyethylene glycol (PEG) can be used to remove DEG so as to improve the stability of the particles and to limit their cytotoxicity. In the course of this project, DEG-Gd2O3 particles were treated with three different polymers: PEG-phosphate, PEG-silane and PEG diacid. In order to determine the functional group that can react strongly with the rare-earth oxide, these polymers were grafted on both Gd2O3 particles and thin films. Different grafting methodologies were developed to identify the optimal reaction conditions. The physicochemical properties of the PEG-Gd2O3 particles and the PEG-treated surfaces were measured with different surface characterization techniques. In conclusion, this study shows that PEG-phosphate reacts more strongly with Gd2O3 nanomaterials compared to the other PEG derivatives. Moreover, PEG-phosphate-Gd2O3 particles have better physicochemical and relaxometric properties than all the other systems studied in this research project (particles covered with DEG, PEG-silane and PEG diacid). These particles might be considered in the future as a potential contrast agent for cellular MRI and could replace the products used currently (mainly iron oxides nanoparticles).
Sironneau, Sandrine. "Corrélation fibrose pancréatique et signal IRM". Bordeaux 2, 2000. http://www.theses.fr/2000BOR23043.
Zhang, Nan. "Feature selection based segmentation of multi-source images : application to brain tumor segmentation in multi-sequence MRI". Phd thesis, INSA de Lyon, 2011. http://tel.archives-ouvertes.fr/tel-00701545.
Bierry, Guillaume. "Imagerie cellulaire en IRM : application en pathologies infectieuses et inflammatoires osseuses". Strasbourg 1, 2008. http://www.theses.fr/2008STR13061.
Cellular imaging using magnetic resonance imaging (MRI) is an emerging new field of development of medical imaging. Cellular imaging is based on the non invasive and in vivo identification of cells of interest in living subjects. Macrophages are keys cells of the immune system and are involved in several pathologic mechanisms such as infection and inflammation. Macrophages can be labelled by MRI contrast agents called Ultrasmall Superparamagnetic Iron Oxyde (USPIO). Those particles are phagocytosed by macrophages and will induce MRI signal modifications in areas with macrophage infiltration. MRI cellular imaging based on USPIO macrophages labelling can be applied in infectious osteomyelitis and can allow a specific characterization of infected areas. Moreover, in reason of a different macrophages distribution, MRI macrophage imaging can allow discrimination of infection from sterile inflammation
Beuf, Olivier. "IRM et biomatériaux prothétiques : caractérisation magnétique et interface avec les tissus vivants". Lyon 1, 1998. http://www.theses.fr/1998LYO10017.
Petibon, Yoann. "Développement de méthodes quantitatives en imagerie simultanée TEP-IRM". Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066187.
The physiologic motion of organs during the data acquisition and the finite system’s Point Spread Function (PSF) both limit the image quality of Positron Emission Tomography (PET). Recently, whole-body (WB) simultaneous PET-Magnetic Resonance (MR) scanners have become available. This modality offers an elegant solution to the motion problem since MR-based motion information can be used to correct the PET images for motion. Nevertheless, to fully benefit from the new capabilities offered by PET-MR, it is essential to also compensate the images for PSF-related degradations. The goal of this thesis was to develop methods allowing to improve PET image quality using PET-MR. In that perspective, we have developed MRI acquisition/processing techniques to measure organs’ motion. We have modeled the spatially-varying PSF using point source measurements. We have then incorporated MR-based motion information (of both emission and attenuation maps) and PSF modeling into fully-3D iterative PET reconstruction, yielding images virtually free of motion artifacts while reducing PSF-related effects. These methods were evaluated for two key applications of WB PET-MR, oncology and cardiology, using phantom, animal and patient studies, demonstrating improved image quality and assessment of tumors and myocardial defects. In addition, we have developed methods allowing to improve PET imaging of small coronary atherosclerotic plaques, a promising pre-clinical application of PET-MR, which were evaluated using a realistic PET-MR simulation study. Overall, the results obtained demonstrate that the developed methodology can substantially improve PET image quality as compared to standard methods
Van, de moortele Pierre-françois. "Irm fonctionnelle cérébrale à 3 Tesla : développements méthodologiques". Paris 11, 1999. http://www.theses.fr/1999PA11T018.
The aim of this work is to optimize functional studies of the human brain on a whole body 3 Tesla MRI scanner. A number of artifacts were to be fixed, mainly related to the Echo Planar Imaging sequence, which affords extremely fast acquisition rates, but is highly sensitive to strong artifacts (distortion, ghost image) and produces a high level of noise. These effects are even worsened at high magnetic field values. We proposed, validated and implemented sorne original methodological approaches to attenuate some artifacts and improve the quality of fMRI studies conducted in the laboratory. We have implemented a correction procedure for image distortions (from P. Jezzard) that we have validated on cerebral activation measurements. To suppress the ghost image, which is characteristic of Echo Planar Imaging, we modified a double sampling technique (from Yang), for continuous phase encoding Echo Planar Imaging, and we wrote a specifie algorithm needed for image reconstruction. To present auditory stimuli in the context of the high level of noise, we designed two modified Echo Planar sequences with the insertion of silent periods to present verbal material to the subject. One sequence is dedicated for blocked design experiments, the other for event-elated paradigms. The modified sequences were also validated in phantom studies. After having shown that sarnpling the brain slice by slice over time produced significant bias in images analysis, we have developed and implemented a correction algorithm to interpolate samples on the first slice acquisition time for each brain volume. Head motions are one of the main sources of unsuccessful fMRI studies. To measure the head position in the magnet, we demonstrate the feasibility of a method based on non proton fiducial markers, the position of which is measured by projections interleaved in the Echo Planat imaging scheme
Frindel, Carole. "Imagerie par résonance magnétique du tenseur de diffusion (IRM-TD) en imagerie cardiaque humaine : traitements et premières interprétations". Lyon, INSA, 2009. http://theses.insa-lyon.fr/publication/2009ISAL0098/these.pdf.
The motivation of this thesis is the study of the spatial organization of cardiac muscle fibers from a series of three-dimensional images acquired by Diffusion Tensor MRI (DT-MRI). This organization is a fundamental property underlying the heart contractile function. However it is very difficult to obtain considering the difficulties inherent to cardiac and respiratory motion. Our goal is to develop new approaches that can cope with physiological motion and noise sensititvity, for the estimation, the analysis and the visualization of myocardial fibers. My work is composed of three main axis. The first compares, in the context of ex vivo clinical studies, the main regularization approaches that operate either on diffusion weighted images or on diffusion tensors. The differences are small enough to conclude that the quality of our DT-MRI data is sufficient to consider all regularization methods as equivalent. The second concerns a new tractography method especially designed for cardiac specificity. It is guided by a global cost functional which allows automatic estimation of cardiac fibers in one shot, without using any initialization points. The latest axis consists in distinguishing a cardiac fibre population into clusters. It is based on the comparison of two classification methods (geometrical and topological type) using three different fibre representation modes. Our results establish that classification may allow automatic identification of myocardial regions from DT-MRI images, which could greatly ease analysis and comparison of these images towards the design of patient-specific therapies
Belaroussi, Boubakeur. "Correction par traitement d'images de l'artéfact de susceptibilité magnétique dans les images IRM". Lyon, INSA, 2005. http://theses.insa-lyon.fr/publication/2005ISAL0072/these.pdf.
In this work, we present CASTI, a new susceptibility artifact correction method based on image processing for anatomical SE and GE images. CASTI allows for both geometric and intensity distortion correction when a field map of the imaged object is known. Susceptibility artefact effects have been modeled by means of a pixel shift map and an intensity distortion map. Those two maps are built from the field map of the imaged object. From an MR Simulator we have modified to include susceptibility artefact simulation, we can build the intensity distortion map of any MR sequence relying on its implementation on the MR simulator. For a given pixel, the correction process consists in its intensity modification by mean of the intensity distortion map and then its shift to its correct position using the pixel shifting map
Denis, de Senneville Baudouin. "Correction des mouvements pour la thermométrie temps réel guidée par IRM". Bordeaux 1, 2005. http://www.theses.fr/2005BOR13123.
Ali, Mayssa. "Études anatomiques et biométriques des cordes vocales par l'imagerie médicale IRM". Lyon 1, 2008. http://www.theses.fr/2008LYO10070.
The aim of the present study was to evaluate in vivo the morphologic parameters and the modifications of the larynx and vocal folds during normal phonation using dynamic MRI. MRI images of the larynx of 10 volunteers aged between 20 et 40 years during speech production were obtained. The volunteers were asked to breathe out long and deep in order to prolong the emission of the vowels [i] (as in key), [a] (as in car), [u] (as in loop) and the consonant [ch] (as in ship) for the entire duration of the scan. We demonstrated the modification of the larynx position, which is high for [i] and low for [u], [a], [ch], and the modification of the vocal folds witch is adducted and abducted in [i], [u], [a] and kept abducted in [ch]. Our study confirm the possibility of using dynamic MRI to visualize the larynx and the mobility of vocal fold during normal phonation in multiple plans with high spatial and temporal resolution
Fournier, Antoine. "Imagerie par résonnance magnétique moléculaire et inflammation des barrières biologiques dans les modèles de sclérose en plaques". Thesis, Normandie, 2017. http://www.theses.fr/2017NORMC410/document.
Developing new strategies to detect disease activity in multiple sclerosis (MS) is essential to improve the diagnosis and follow-up of this pathology. To this aim, we used microparticles of iron oxide (MPIO) coupled to an antibody specific to the P-selectin or MAdCAM-1 protein. In this thesis, we establish that molecular MRI specific to P-selectin protein is able to detect the pathological events that take place in the spinal cord of chronic and relapsing-remitting models of MS in mice. Interestingly, we show here that this MRI technique can predict the apparition of relapses and recoveries in EAE. Moreover, we demonstrate that MRI specific to MAdCAM-1 protein is able to detect the gut inflammation that takes place in models of bowel diseases or MS. The innovative MRI techniques developed in this study could bring new advances in the diagnosis and prognosis of MS relapses by targeting gut inflammation. In the last part of this work, we report that the glymphatic system also exists in the spinal cord parenchyma of the mouse. In EAE, the activity of this system is reduced in the spinal cord but not in the brain or cerebellum. This alteration is associated to inflammatory cell accumulation within the perivascular space, AQP4 disorganization and leads to a large increase of ventricular volume. These disruptions could contribute to the MS pathophysiology. Our results hold significant promise for the development of new therapeutic strategies
Ducreux, Denis. "Etudes des shunts artério-veineux cérébraux en imagerie par résonance magnétique (IRM) de perfusion". Paris 11, 2005. http://www.theses.fr/2005PA112188.
Introduction: Brain Arteriovenous shunts are diseases that induce seizures, headaches and focal deficits. We studied their pathophysiology using 1. 5 T Perfusion MR trying to relate hemodynamics abnormalities and symptoms. Material and Methods: 39 patients and 10 healthy subjects were included. We performed perfusion MRI on a 1. 5 T scanner with Gd bolus injection. MRI series were processed using indicator dilution theory CBV and CBF parameters were estimated in two specific brain areas using four arterial input function estimations: "Local", "Regional", "Regional Scaled", and 'Global". Best of these AIF estimates was assessed using the NGS statistical method. We then compared patients and volunteers CBV and CBF results trying to relate symptoms and perfusion abnormalities using Fisher, Cramer, Chi square and Phi tests. Results: Patients CBV and CBF values were different to those estimated in volunteers in all AIF estimates. Three perfusion abnormalities were observed: hypo, hyperperfusion and venous congestion in 91% of patients. The best AIF estimate assessed using NGS was "Regional Scaled", with significant relation between hyperperfusion and seizures. Conclusion: We observed a significant relation between hyperperfusion and seizures in the AVS patients
Carme, Sabin. "Modélisation de la perfusion quantitative en imagerie par résonance magnétique (IRM) cardiaque in-vivo". Lyon, INSA, 2004. http://theses.insa-lyon.fr/publication/2004ISAL0002/these.pdf.
A parametrical analysis of contrast agent distribution is proposed to interpret first pass MR images and to quantificate the myocardial perfusion. We are concerned with the correction of spatial intensity variations in images. Furthermore, we are interested in the application of a robust NMR signal processing technique and deconvolution techniques adapted to low signal-to-noise ratio. Data sets were provided, close to clinical conditions, using in-vivo experiments applying several pharmacological stresses on ischemics pigs presenting a stenosis of the left circumflex coronary artery. The agreement and accuracy measurements between observers are respectively 57. 1% and 53. 1% for visual analysis, and 81. 2% and 81. 1% for parametric map analysis. A linear relationship between perfusion parameters and radioactives microspheres is established for low blood flows<250 ml/100g/min, i. E. On the signal variation SI y=0. 06x+6, r=0. 82, the ascending up-slope y=0. 026+2, r=0. 79 and the regional blood flow rMBF y=2. 9+130, r=0. 76. Considering high flows, the MR intensity curves in blood and myocardial tissue are attenuated leading to an under-estimation of the measured parameters. The signal variations depending on the relaxation rate R1 is modeled considering water exchange in the tissue. We have shown, on a series of images at rest and under stress, that the coronary reserve is 3. 87 for flows measured with R1 and an inter imaging mediate water exchange rate whereas the coronary reserve is 2. 87 for MR signal intensity measured flows. Finally, we have shown on a series of images, at rest and under stress, that the calculation of physiologic parametric maps in each pixel is possible while applying a spatial regularization technique considering discontinuities to smooth the parametric image
Rico-Lamy, Audrey. "Caractérisation fonctionnelle du système moteur au stade précoce de la sclérose en plaques : approche par stimulation magnétique transcrânienne et imagerie fonctionnelle par résonnance magnétique". Thesis, Aix-Marseille 2, 2011. http://www.theses.fr/2011AIX20724.
Multiple sclerosis (MS) is a chronic inflammatory demyelinating disorder of the central nervous system which is frequently responsible for motor disability. Better assessment of pathophysiological process implicated in motor system dysfunction (cortico-spinal tract or more diffuse tissue damage) as well as the compensatory mechanises are critical in the understanding and the prevention of disability. Their study in the early stage of the disease will allow to a better understanding of the links between tissue injury, compensatory mechanisms and functional consequences. We have better characterized functional dysfunction of the central motor pathway at the early stage of multiple sclerosis. We have also evidenced the influence of diffuse brain injury on functional motor cortical reorganization. Last, we have demonstrated the existence of a basal functional plasticity at rest of the nondominant motor network that is correlated with its functional plasticity during action
Gensanne, David. "Réalisation d'un nouveau gel ferreux équivalent-tissu : applications en dosimétrie volumique par imagerie de résonance magnétique (IRM)". Toulouse 3, 2003. http://www.theses.fr/2003TOU30077.
To improve the efficiency of radiotherapy treatments various new radiotherapy techniques have been developed, including inverse therapy planning, multileaf collimators, stereotactic radiotherapy and radiosurgery. These new conformal irradiation techniques generally create rather complicated dose distributions in the irradiated volume and classical dosimeters are not available to easily and accurately perform 3D measurements of the absorbed dose. In practice, up to now, no reference dosimeter has got general approval but magnetic resonance imaging (MRI) dosimetry using tissue-equivalent ferrous or polymer gels, seems a promising technique which could serve, in the future, as a reference to determine 3D dose distributions. Compared to polymer gels, ferrous gels are less sensitive and furthermore the diffusion of ferric ions created by irradiation causes a gradual blurring of the radiation dose pattern with time. However, contrary to polymer gels, ferrous gels have no toxicity, are easier to use and cheaper, so, we focused in this work on the development of a new ferrous gel with improved sensitivity and diffusion. .