SPECTRAL CLUSTERING BASED PARCELLATION OF FETAL BRAIN MRI

Many neuroimaging studies are based on the idea that there are distinct brain regions that are functionally or micro-anatomically homogeneous. Obtaining such regions in an au-tomatic way is a challenging task for fetal data due to the lack of strong and consistent anatomical features at the early stages of brain development. In this paper we propose the use of an automatic approach for parcellating fetal cerebral hemi-spheric surfaces into K regions via spectral clustering. Unlike previous methods, our technique has the crucial advantage of only relying on intrinsic geometrical properties of the corti-cal surface and thus being unsupervised. Results on a data-set of fetal brain MRI acquired in utero demonstrated a convinc-ing parcellation reproducibility of the cortical surfaces across fetuses with varying gestational ages and folding magnitude

In Vivo High-Resolution 7 Tesla MRI Shows Early and Diffuse Cortical Alterations in CADASIL

Background and Purpose: Recent data suggest that early symptoms may be related to cortex alterations in CADASIL (Cerebral Autosomal-Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy), a monogenic model of cerebral small vessel disease (SVD). The aim of this study was to investigate cortical alterations using both high-resolution T2* acquisitions obtained with 7 Tesla MRI and structural T1 images with 3 Tesla MRI in CADASIL patients with no or only mild symptomatology (modified Rankin's scale = 24). Methods: Complete reconstructions of the cortex using 7 Tesla T2* acquisitions with 0.7 mm isotropic resolution were obtained in 11 patients (52.1 +/- 13.2 years, 36% male) and 24 controls (54.8 +/- 11.0 years, 42% male). Seven Tesla T2* within the cortex and cortical thickness and morphology obtained from 3 Tesla images were compared between CADASIL and control subjects using general linear models. Results: MMSE, brain volume, cortical thickness and global sulcal morphology did not differ between groups. By contrast, T2* measured by 7 Tesla MRI was significantly increased in frontal, parietal, occipital and cingulate cortices in patients after correction for multiple testing. These changes were not related to white matter lesions, lacunes or microhemorrhages in patients having no brain atrophy compared to controls. Conclusions: Seven Tesla MRI, by contrast to state of the art post-processing of 3 Tesla acquisitions, shows diffuse T2* alterations within the cortical mantle in CADASIL whose origin remains to be determined

Discutindo a educação ambiental no cotidiano escolar: desenvolvimento de projetos na escola formação inicial e continuada de professores

A presente pesquisa buscou discutir como a Educação Ambiental (EA) vem sendo trabalhada, no Ensino Fundamental e como os docentes desta escola compreendem e vem inserindo a EA no cotidiano escolar., em uma escola estadual do município de Tangará da Serra/MT, Brasil. Para tanto, realizou-se entrevistas com os professores que fazem parte de um projeto interdisciplinar de EA na escola pesquisada. Verificou-se que o projeto da escola não vem conseguindo alcançar os objetivos propostos por: desconhecimento do mesmo, pelos professores; formação deficiente dos professores, não entendimento da EA como processo de ensino-aprendizagem, falta de recursos didáticos, planejamento inadequado das atividades. A partir dessa constatação, procurou-se debater a impossibilidade de tratar do tema fora do trabalho interdisciplinar, bem como, e principalmente, a importância de um estudo mais aprofundado de EA, vinculando teoria e prática, tanto na formação docente, como em projetos escolares, a fim de fugir do tradicional vínculo “EA e ecologia, lixo e horta”.Facultad de Humanidades y Ciencias de la Educació

Compréhension et maîtrise des effets de susceptibilité magnétique air/matière en imagerie par résonance magnétique (application à la caractérisation desproduits alvéolés dans les procédés agroalimentaires)

L idée originale de cette thèse est d utiliser les effets de susceptibilité magnétique pour caractériser les matrices alimentaires renfermant des interfaces de susceptibilité air/eau. Ainsi, on sort d une logique de correction pour un autre type de contraste et moyen de quantification. On pense la susceptibilité magnétique comme un paramètre utile de caractérisation dans la mesure où elle est intrinsèque au produit étudié, modifie localement les intensités selon certains paramètres d acquisition et peut donc constituer une signature du milieu d intérêt. Pour cela, nous avons mené une étude frontale pendant cette thèse: à l aide de la simulation IRM et d expériences IRM. Une première partie du travail a consisté à intégrer dans le simulateur la modélisation du déphasage intravoxel puis à valider quantitativement le simulateur dans le cas d un objet simple (cylindre d air entouré d eau) et d un objet plus complexe (ensemble de petits cylindres d air entourés d eau) en confrontant résultats de simulation et expérimentaux. Nous avons ensuite étudié et modélisé en simulation le signal en présence d ensembles de bulles. Ces résultats ont permis de définir une stratégie d estimation de la taille des bulles dans la pâte à pain. Les objets d étude ont été la pâte juste pétrie (sans ferment) et la pâte en cours de fermentation qui présentent des effets de susceptibilité dus aux nombreuses bulles de gaz. Enfin, nous avons étudié la porosité dans les tissus de la tomate qui renferment de petites bulles d air.The original idea of the present thesis is to use magnetic susceptibility effects as a mean to characterize food products containing air/water interfaces. While methods exist to correct these artefacts, we considered magnetic susceptibility as an interesting contrast agent as dependent of field inhomogeneities induced by the object itself. A dual approach was conducted by comparing simulated and experimental results. First step was to integrate intravoxel dephasing modeling in the MRI simulator. Validation was then quantitatively done on a single air-filled cylinder and on a network of small interacting air-filled cylinders. Signal loss in presence of air bubbles was studied in simulation. We could model the signal decay constant as a function of porosity and bubble radius. These results lead to a MRI method based on magnetic susceptibility effects to estimate bubble size in alveolar products. This was applied to bread dough at rest and during proving. Finally, an original method, based on spin echo and gradient echo sequences, was developed to quantify porosity in tomato tissues.RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF

MODEL-DRIVEN PARAMETERIZATION OF FETAL CORTICAL SURFACES

Surface-based analysis is a tool of choice to study the anatomy and function of the cortex in adult and children brains. Common surface registration approaches are not adaptable to fetal data since data-driven mapping techniques are limited by the lack of structural features across all ges-tational ages. In this work, we adapt the HIP-HOP model-driven cortical surface parameterization method to the spe-cific problem of defining correspondences across fetuses with different gestational ages. We demonstrate the validity of our approach by quantifying the curvature evolution during de-velopment. Our findings are highly consistent with previous studies. This work is the first demonstration of the feasibility of applying surface-based mapping and analysis to fetal data

Magnetic resonance imaging method based on magnetic susceptibility effects to estimate bubble size in alveolar products: application to bread dough during proving.

Magnetic resonance imaging has proven its potential application in bread dough and gas cell monitoring studies, and dynamic processes such as dough proving and baking can be monitored. However, undesirable magnetic susceptibility effects often affect quantification studies, especially at high fields. A new low-field method is presented based on local assessment of porosity in spin-echo imaging, local characterization of signal loss in gradient-echo imaging and prediction of relaxation times by simulation to estimate bubble radii in bread dough during proving. Maps of radii showed different regions of dough constituting networks which evolved during proving. Mean radius and bubble distribution were assessed during proving

SPANOL (SPectral ANalysis of Lobes): A Spectral Clustering Framework for Individual and Group Parcellation of Cortical Surfaces in Lobes

International audienceUnderstanding the link between structure, function and development in the brain is a key topic in neuroimaging that benefits from the tremendous progress of multi-modal MRI and its computational analysis. It implies, inter alia, to be able to parcellate the brain volume or cortical surface into biologically relevant regions. These parcellations may be inferred from existing atlases (e.g., Desikan) or sets of rules, as would do a neuroanatomist for lobes, but also directly driven from the data (e.g., functional or structural connectivity) with minimum a priori. In the present work, we aimed at using the intrinsic geometric information contained in the eigenfunctions of Laplace-Beltrami Operator to obtain parcellations of the cortical surface based only on its description by triangular meshes. We proposed a framework adapted from spectral clustering, which is general in scope and suitable for the co-parcellation of a group of subjects. We applied it to a dataset of 62 adults, optimized it and revealed a striking agreement between parcels produced by this unsupervised clustering and Freesurfer lobes (Desikan atlas), which cannot be explained by chance. Constituting the first reported attempt of spectral-based fully unsupervised segmentation of neuroanatomical regions such as lobes, spectral analysis of lobes (Spanol) could conveniently be fitted into a multimodal pipeline to ease, optimize or speed-up lobar or sub-lobar segmentation. In addition, we showed promising results of Spanol on smoother brains and notably on a dataset of 15 fetuses, with an interest for both the understanding of cortical ontogeny and the applicative field of perinatal computational neuroanatomy

Are Developmental Trajectories of Cortical Folding Comparable Between Cross-sectional Datasets of Fetuses and Preterm Newborns?

Magnetic resonance imaging has proved to be suitable and efficient for in vivo investigation of the early process of brain gyrification in fetuses and preterm newborns but the question remains as to whether cortical-related measurements derived from both cases are comparable or not. Indeed, the developmental folding trajectories drawn up from both populations have not been compared so far, neither from cross-sectional nor from longitudinal datasets. The present study aimed to compare features of cortical folding between healthy fetuses and early imaged preterm newborns on a cross-sectional basis, over a developmental period critical for the folding process (21-36 weeks of gestational age [GA]). A particular attention was carried out to reduce the methodological biases between the 2 populations. To provide an accurate group comparison, several global parameters characterizing the cortical morphometry were derived. In both groups, those metrics provided good proxies for the dramatic brain growth and cortical folding over this developmental period. Except for the cortical volume and the rate of sulci appearance, they depicted different trajectories in both groups suggesting that the transition from into ex utero has a visible impact on cortical morphology that is at least dependent on the GA at birth in preterm newborns

A new corrective model to evaluate TBS in obese post-menopausal women: a cross-sectional study

The relationship between post-menopausal osteoporosis and obesity has been mainly investigated using bone mineral density (BMD) as marker of bone health. Since BMD does not reflect bone microarchitecture, another analytical tool, the Trabecular Bone Score (TBS), has been recently developed for this purpose. In this study, we intended to investigate the validity of TBS as marker of bone quality in obese post-menopausal women

Alteration of the Cortex Shape as a Proxy of White Matter Swelling in Severe Cerebral Small Vessel Disease

International audienceCADASIL is a monogenic small vessel disease characterized by the accumulation of brain tissue lesions of microvascular origin leading to strokes and cognitive deficits. Both cortical and parenchymal alterations have been described using various MRI markers. However, relationships between cortical and subcortical alterations remain largely unexplored. While brain atrophy is a preponderant feature in cerebral small vessel disease, recent results in CADASIL suggest slightly larger brain volumes and increased white matter water content at early stages of the disease by comparison to controls. We hypothesized in this study that increased water content in gyral white matter balances expected brain atrophy. Direct white matter volume computation is challenging in these patients given widespread subcortical alterations. Instead, our approach was that a gyral white matter swelling would translate into a modification of the shape of cortical gyri. Our goal was then to assess the relationship between subcortical lesions and possible alteration of the cortex shape. More specifically, aims of this work were to assess 1) morphometric differences of the cortex shape between CADASIL patients and controls 2) the relationship between the cortex shape and the volume of white matter hyperintensities (WMH), a reflect of white matter alterations. Twenty-one patients at the early stage of the disease and 28 age-and sex-matched controls were included. Cortical surfaces were reconstructed from 3D-T1-weighted images. Folding power assessed from spectral analysis of gyrification and cortical morphometry using curvedness and shape index were computed as proxies of the cortex shape. Influence of segmentation errors were evaluated through the simulation of WMH in controls. As a result, patients had larger folding power and curvedness compared to controls. They also presented lower shape indices both related to sulci and gyri. In patients, the volume of WMH was associated with decreased gyral shape index. These results suggest that the cortex shape of CADASIL patients is different compared to controls and that the enlargement of gyri is related to the extent of white matter alterations. The study of the cortex shape might be another way to evaluate subcortical swelling or atrophy in various neurological disorders