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Дисертації з теми "Imagerie par résonance magnétique de diffusion – Dissertation universitaire":
Jissendi, Tchofo Patrice. "Les dysplasies cérébelleuses : corrélations anatomo-fonctionnelles." Phd thesis, Université du Droit et de la Santé - Lille II, 2011. http://tel.archives-ouvertes.fr/tel-00635755.
Le, Bars Anne-Lise. "Développements méthodologiques pour l’IRM de diffusion cardiaque." Electronic Thesis or Diss., Université de Lorraine, 2021. http://www.theses.fr/2021LORR0089.
Diffusion magnetic resonance imaging (MRI) is a non-invasive imaging modality that allows the assessment of microarchitecture in biological tissues. Knowing the arrangement of myocardial fiber is important to fully understand cardiac electrophysiology in patients, and therefore to improve the treatment of complex arrythmia such as ventricular tachycardia. Nevertheless, efforts have to be made to apply diffusion MRI to moving organs because of the various artefacts created by displacements. Macroscopic motion, including cardiac contraction and breathing is in the range of a few millimeters, whereas diffusion motion is at the micrometer scale. To deal with cardiac motion, a cardiac-triggered diffusion-weighted spin-echo echo planar imaging sequence can be used with first and second order motion-compensated diffusion-encoding gradients. However, these sequences are very sensitive to the phase of the cardiac cycle chosen to perform the acquisition. Moreover, the ventricle coverage is often limited to a few slices due to the long scan time required to have sufficient SNR. Considering these limitations, the thesis has been separated in two parts with the following objectives: to implement a subject-specific cardiac synchronization and to set up an efficient protocol that performs a full coverage of the left-ventricle with isotropic resolution. The subject-specific cardiac synchronisation has been implemented using a real-time phase contrast (RTPC) sequence which is sensitive to motion. RTPC sequence provides knowledge on the variability in duration of cardiac phases. By modelling the cardiac variability, it was possible to study the quality of the diffusion measurement as a function of the cardiac phase. In regards of the results, the sequence can be valuable to optimize and/or adapt the trigger delay to target the diastasis. This phase is the quiescent phase of the cardiac cycle but also the most variable as a function of heart-rate. The online reconstruction of RTPC sequence has been successfully implemented to facilitate the deployment of the sequence to adapt the trigger delay for future clinical research, possibly with other applications. The focus of the second part of the work was to retrieve tri-dimensional information about myocardial fiber organisation with a full coverage of left ventricle. This full coverage is mandatory to simulate cardiac electrophysiology. A bulk motion-corrected super-resolution approach to cDTI has been proposed to improve spatial resolution without significant cost on SNR. Therefore, the total scan time can be reduced by this method. Evaluation in a numerical heart phantom and in a physical helicoidal phantom, have shown the improvement of spatial resolution and diffusion tensor estimation in a general case (except when the underlying geometry is highly favorable to low resolution images). This is of particular interest when there are significant changes in orientation of principal diffusion direction along the slice direction, according to the global geometry of the heart. The feasibility of super-resolution in-vivo cDTI on healthy volunteers has shown the applicability of the approach
Guevara, Olivares Miguel. "Disentangling the short white matter connections using a fiber's geometry based dimensional reduction approach." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPAST053.
The study of superficial white matter (SWM) has often been left aside, mainly because of its high variability. Higher quality acquisition methods and the development of new analysis tools have facilitated the study of SWM from diffusion MRI and tractography. Brain connectivity and cortical folding pattern must be strongly related, especially for short U-fibers, which circumvent the folds. As the folding patterns morphology is specific to each human being, so should be the underlying fibers configuration. In this work we created a pipeline to disentangle the short white matter connections into their different configurations and to characterize their relation with other structures.First a method to delineate short bundles from a tractography set was built using a hybrid approach, by extracting fibers connecting two cortical regions of interest (ROIs) (incorporating anatomical information) and then clustering them into bundles (considering their shape), reproducible across subjects. Subjects were aligned by a T1-based affine transformation and a deterministic tractography database (79 subjects) was used. This generated a whole brain streamline bundle atlas, which allows distance-based segmentation of the bundles in new subjects, in order to perform clinical studies over specific connections. The bundles obtained were compared against other two publicly available atlases (using alternative non-linear alignment across subjects), to evaluate their reproducibility given different methods and databases. A non-negligible number of bundles were found similar among the three atlases. As SWM bundle definition is still a subjective matter, over-segmentation can nevertheless occur. However, even greater granularity is required when aiming to classify the different bundle configurations. This level of disentanglement was achieved by an ISOMAP dimensionality reduction algorithm. It aimed to stratify the population based on their fibers using geometrical changes across subjects. For each region under study, the fibers surrounding a specific sulcus were targeted and therefore the ROIs were selected accordingly. These regions are: central sulcus, superior temporal sulcus, cingulate sulcus and precentral gyrus. The method was applied over 816/897 subjects of the S900 release of the HCP database and a preprocessed probabilistic tractography database. For each region the fibers were extracted, sampled and then used in the ISOMAP computation, which in turn was employed to split the population in ten groups. In each group a refined version of a short bundle identification method was applied, in order to obtain reproducible bundles. These were then automatically matched with their corresponding ones in the other groups, based on a centroid fiber distance. A Hysteresis principle was used to recover missing bundles (previously discarded) in each group. In order to identify the bundles driving the differences reflected on each ISOMAP dimension, the correlation of the fibers geometry with the subjects ISOMAP values was performed, by using a “bundle to tractogram” distance for each pair of subjects. The fiber-based ISOMAP values were also compared to a sulcus-based ones, obtaining a high correlation for the first dimension. The bundles showing correlation with the ISOMAP values show coherent morphological transitions along the groups, and are located in areas where the sulcus also exhibits differences in shape. Moreover, the bundles are also spatially correlated to changes in functional activations. These results prove the link between the brain wiring and the cortical folding pattern. Moreover, they evidence that a finer delineation of the bundles allow the detection of differences that most of the time are blurred out due to the mixing of configurations
Gkamas, Theodosios. "Modélisation statistique de tenseurs d'ordre supérieur en imagerie par résonance magnétique de diffusion." Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAD036/document.
DW-MRI is a non-invasive way to study in vivo the structure of nerve fibers in the brain. In this thesis, fourth order tensors (T4) were used to model DW-MRI data. In addition, the problems of group comparison or individual against a normal group were discussed and solved using statistical analysis on T4s. The approaches use nonlinear dimensional reductions, assisted by non-Euclidean metrics for T4s. The statistics are calculated in the reduced space and allow us to quantify the dissimilarity between the group (or the individual) of interest and the reference group. The proposed approaches are applied to neuromyelitis optica and patients with locked in syndrome. The derived conclusions are consistent with the current medical knowledge
Durand, Matthieu. "Imagerie expérimentale ex vivo de haute résolution à 7 tesla du cancer localisé de la prostate." Thesis, Lille 2, 2019. http://www.theses.fr/2019LIL2S015/document.
Prostate MRI at 1.5T or 3T is the best imaging modality for tumor detection. Weinvestigated high resolution MRI at 7T on prostate specimen tissue to improve spatialresolution and prostate cancer detection.First part of experiments consisted of setting up new imaging protocol with 7T MRI onex vivo prostatic tissue. Imaging was carried out on all or part of specimen from radicalprostatectomy of patients or prostate harvested from deceased organ donors.Collected data resulted in new protocol parameters for fast spin echo needed to yielda spatial resolution of 60 X 60 X 90 μm3. High spatial resolution imaging was used toidentify relevant morphological structures for characterization of the prostate gland andtumor as compared to histology.Second part of work was done with whole gland imaging at 7T of radical prostatectomyspecimens of patients. Imaging protocol was based on the outcomes from the first partof experiments and consisted in T2W with high resolution of 130 X130 X195 μm3,diffusion and ADC map. Two independent and blinded reviewers were in charge ofimaging quality assessment and tumor detection. Overall quality was great with goodagreement between the two reviewers. Correlation study for prostate cancer detectionwith the corresponding H&E was of 70%, 80%, 79% and 72% for sensitivity, specificity,positive predictive value and negative predictive value, respectively.We measured the resolution of 7T MRI of ex vivo prostatic tissue, and it’s benefits intumor detection. New semiology should be designed at 7T to improve theunderstanding of prostatic tissue in further experiments. In future, these findings canbe extrapolated to carry out in 7T MRI of in vivo prostate gland
Ameller, Aurély. "Les troubles de la familiarité dans la schizophrénie." Phd thesis, Université du Droit et de la Santé - Lille II, 2014. http://tel.archives-ouvertes.fr/tel-01061407.
Pfaff, Line. "Modifications émotionnelles dans la sclérose en plaques : étude en neuropsychologie et neuroimagerie." Thesis, Strasbourg, 2018. http://www.theses.fr/2018STRAJ022/document.
Emotional disorders in multiple sclerosis (MS) are frequently described as difficulties in recognizing facial expression. Yet, emotional experience is insufficiently studied in MS, and its neurobiological correlates stays never explored. Moreover, interaction between emotional disorder and other variable remains little documented, especially for alexithymia, a very frequent trouble in MS which could also cause emotional disturbances. The scope of this work is to explore positive and negative emotions in MS, with a focus on the recognition and experience dimensions. Concerning the emotional experience, brain functional activation correlates are also explored in MS overall, and in alexithymics versus non alexithymics MS subjects especially. A first study confirmed the difficulty for MS patient in recognizing facial emotions, and those difficulties were more marked for negative emotions. This study also highlights a more scattered emotional experience in MS, with a global exacerbation of their pleasant as well as unpleasant emotional feeling. A second study with fMRI shows that this scattered emotional experience was sustained by more brain functional variability during the emotional task. It takes place in brain structures known for their implication for the subjective feeling construction. Further diffusion imaging analyses support the view of a brain dysconnexion in those functional anomalies centred on limbic loop and fronto-insula network, also called salience network. A third study highlights a specific contribution of alexithymia in brain activity for hedonics experience, centred on insula deactivations whereas anhedonics experience seems to be influenced by the diseases and comorbid alexithymia. Brain diffusion analyses were independent of the alexithymia status. Thus, MS patients show difficulties in identifying emotion and have modifications of their own pleasant and unpleasant emotional experience. The frequent comorbid alexithymia in MS exacerbates those troubles in the same way as the lesion phenomenon of MS. Considering the implications that emotional disorders may have for MS patients as well as their familial, social and professional entourage, it seems essential to take these aspects into account for a better management of MS
Delattre, Claire. "Approches physiopathologiques des interactions entre accident vasculaire cérébral et démence vasculaire." Phd thesis, Université du Droit et de la Santé - Lille II, 2013. http://tel.archives-ouvertes.fr/tel-00982049.
Pontabry, Julien. "Construction d'atlas en IRM de diffusion : application à l'étude de la maturation cérébrale." Thesis, Strasbourg, 2013. http://www.theses.fr/2013STRAD039/document.
Diffusion weighted MRI (dMRI) is an in vivo imaging modality which raises a great interest in the neuro-imaging community. The intra-structural information of cerebral tissues is provided in addition to the morphological information from structural MRI (sMRI). These imaging modalities bring a new path for population studies, especially for the study in utero of the normal humanbrain maturation. The modeling and the characterization of rapid changes in the brain maturation is an actual challenge. For these purposes, this thesis memoir present a complete processing pipeline from the spatio-temporal modeling of the population to the changes analyze against the time. The contributions are about three points. First, the use of high order diffusion models within a particle filtering framework allows to extract more relevant descriptors of the fetal brain, which are then used for image registration. Then, a non-parametric regression technique was used to model the temporal mean evolution of the fetal brain without enforce a prior knowledge. Finally, the shape changes are highlighted using features extraction and selection methods
Tasserie, Jordy. "Functional Neuro-Imaging Study of Deep Brain Stimulation Mechanisms for the Restoration of Consciousness Using a Non-Human Primate Mode Pypreclin: An Automatic Pipeline for Macaque Functional MRI." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASL051.
Severe brain injuries may lead to the disruption of long-range inter-region brain communications resulting in chronic Disorders of Consciousness (DoC). Electrical Deep Brain Stimulation (DBS) of the Thalamus has been reported to modulate arousal and ameliorate behavior in Minimally Conscious State (MCS) patients. However, there is no clear demonstration of the cerebral mechanisms for the specific and causal restoration of conscious access, i.e. awareness, with DBS. Here we hypothesized that specific thalamic DBS might restore both arousal and awareness through the restoration of thalamo-cortical activity and the subsequent reorganization of cortical dynamics. We first designed an experimental set-up combining DBS and functional Magnetic Resonance Imaging (fMRI) in Non-Human Primate (NHP) and applied finely tuned anesthesia to suppress consciousness. We recorded whole brain activity and developed a preprocessing pipeline, Pypreclin, to tackle the electrode-induced artifact. During deep sedation, Centro-Median Thalamic (CMT) DBS robustly induced arousal in an ON-OFF fashion. When CMT DBS was switched ON, fMRI signal increased in prefrontal, parietal and cingulate cortices, and gradually returned to baseline seconds after the stimulator was turned OFF. Moreover, CMT DBS led to a reconfiguration of Resting State cortical dynamics bydecreasing the function-structure similarity, previously described as a consciousness signature. Finally, CMT DBS restored a broad hierarchical response to global auditory regularities that was disrupted under general anesthesia. Thus, CMT DBS restored the two main dimensions of consciousness, i.e. arousal and awareness, paving the way to its therapeutical translation in patients with chronic DoC