Cellular detection in cardiac magnetic resonance imaging

Objectifs : Les thérapies régénératives cardiaques ont connu un essor considérable au cours des 10 dernières années. Malgré des effets positifs démontrés chez l’animal, les bénéfices cliniques obtenus chez l’homme sont encore relativement modestes. L’objectif de ce travail a été de mieux comprendre les facteurs liés à l’implantation des cellules souches grâce aux techniques de détection cellulaire en imagerie par résonance magnétique (IRM), afin d’optimiser la thérapie cellulaire cardiaque.Matériel et méthodes : Un protocole de détection cellulaire en IRM cardiaque in vivo ainsi qu’une méthode de détection des microvaisseaux en IRM cardiaque ex vivo haute résolution avec des séquences Susceptibility Weighted Imaging (SWI) ont été développés, puis mis en application pour l’étude de la vectorisation de progéniteurs des cellules endothéliales marqués magnétiquement par des nanoparticules d’oxyde de Fer et injectés par voie intraveineuse, ainsi que pour l’évaluation de l’intégration et de l’efficacité de cellules souches mésenchymateuses administrées via des patchs de fibrine cellularisés chez des rats adultes indemnes de toute pathologie (un groupe contrôle vs un groupe infarctus via ligature définitive de l’artère interventriculaire antérieure).Résultats : Après injection intraveineuse et malgré la vectorisation magnétique (n=16 rats), l’imagerie de détection cellulaire a montré qu’aucune cellule n’était implantée dans le myocarde et que les paramètres fonctionnels cardiaques n’étaient pas améliorés. Avec les patchs cellularisés (n=37 rats), la fraction d’éjection ventriculaire gauche (FEVG) était améliorée dans les groupes de patchs cellularisés par rapport aux groupes contrôles. La densité microvasculaire était augmentée dans la zone infarcie et peri-infarcie dans les groupes cellularisés par rapport aux groupes contrôles, à la fois en immunohistochimie et en IRM sur les séquences SWI. L’IRM a montré l’absence de migration des cellules dans le myocarde à partir du patch, confirmé en immunohistochimie. La persistance de cellules dans la zone d’implantation du patch à la surface épicardique à J21 post greffe et l’étude en cytométrie en flux des cytokines et facteurs de croissance produits par les cellules souches plaident pour une efficacité de la thérapie cellulaire en rapport avec la sécrétion de facteurs paracrines par les cellules souches.Conclusion : L’imagerie de susceptibilité magnétique permet d’une part d’étudier les vaisseaux myocardiques sur des séquences pondérées en SWI ex vivo et d’autre part d’évaluer l’implantation des cellules souches sur des séquences en écho de gradient T2* in vivo. Ces techniques ont permis de mieux caractériser le mode d’action des patchs cardiaques en tant que réservoir de facteurs paracrines pour le traitement de l’insuffisance cardiaque dans un modèle murin. Ces résultats confirment l’intérêt fort à développer et optimiser l’utilisation de biomatériaux intelligents délivrant spécifiquement des molécules d’intérêt comme les cytokines ou les facteurs de croissance et permettant ainsi de contourner les contraintes immunogènes et tératogènes liés aux cellules souches.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

Wavelet-Based Multiscale Initial Flow For Improved Atlas Estimation in the Large Diffeomorphic Deformation Model Framework

Modelling the mean and variability in a population of images, a task referred to as atlas estimation, remains very challenging, especially in a clinical setting where deformations between images can occur at multiple scales. In this paper, we introduce a coarse-to-fine strategy for atlas estimation in the Large Deformation Diffeomorphic Metric Mapping framework, based on a finite parametrization of the subjects' velocity field. Using the Haar Wavelet Transform, a multiscale representation of the initial velocity fields is computed in order to optimize the template-to-subject deformations in a coarse-to-fine fashion. This reparametrization preserves the reproducing kernel Hilbert space structure of the velocity fields, enabling the algorithm to perform efficiently gradient descent. Numerical experiments on three different datasets, including a dataset of abnormal fetal brain images, show that compared to the original algorithm, the coarse-to-fine strategy reaches higher performance and yields template images that preserve important details while avoiding unrealistic features

Wavelet-Based Multiscale Initial Flow For Improved Atlas Estimation in the Large Diffeomorphic Deformation Model Framework

Modelling the mean and variability in a population of images, a task referred to as atlas estimation, remains very challenging, especially in a clinical setting where deformations between images can occur at multiple scales. In this paper, we introduce a coarse-to-fine strategy for atlas estimation in the Large Deformation Diffeomorphic Metric Mapping framework, based on a finite parametrization of the subjects' velocity field. Using the Haar Wavelet Transform, a multiscale representation of the initial velocity fields is computed in order to optimize the template-to-subject deformations in a coarse-to-fine fashion. This reparametrization preserves the reproducing kernel Hilbert space structure of the velocity fields, enabling the algorithm to perform efficiently gradient descent. Numerical experiments on three different datasets, including a dataset of abnormal fetal brain images, show that compared to the original algorithm, the coarse-to-fine strategy reaches higher performance and yields template images that preserve important details while avoiding unrealistic features

Wavelet-Based Multiscale Initial Flow For Improved Atlas Estimation in the Large Diffeomorphic Deformation Model Framework

Modelling the mean and variability in a population of images, a task referred to as atlas estimation, remains very challenging, especially in a clinical setting where deformations between images can occur at multiple scales. In this paper, we introduce a coarse-to-fine strategy for atlas estimation in the Large Deformation Diffeomorphic Metric Mapping framework, based on a finite parametrization of the subjects' velocity field. Using the Haar Wavelet Transform, a multiscale representation of the initial velocity fields is computed in order to optimize the template-to-subject deformations in a coarse-to-fine fashion. This reparametrization preserves the reproducing kernel Hilbert space structure of the velocity fields, enabling the algorithm to perform efficiently gradient descent. Numerical experiments on three different datasets, including a dataset of abnormal fetal brain images, show that compared to the original algorithm, the coarse-to-fine strategy reaches higher performance and yields template images that preserve important details while avoiding unrealistic features

Wavelet-Based Multiscale Initial Flow For Improved Atlas Estimation in the Large Diffeomorphic Deformation Model Framework

Modelling the mean and variability in a population of images, a task referred to as atlas estimation, remains very challenging, especially in a clinical setting where deformations between images can occur at multiple scales. In this paper, we introduce a coarse-to-fine strategy for atlas estimation in the Large Deformation Diffeomorphic Metric Mapping framework, based on a finite parametrization of the subjects' velocity field. Using the Haar Wavelet Transform, a multiscale representation of the initial velocity fields is computed in order to optimize the template-to-subject deformations in a coarse-to-fine fashion. This reparametrization preserves the reproducing kernel Hilbert space structure of the velocity fields, enabling the algorithm to perform efficiently gradient descent. Numerical experiments on three different datasets, including a dataset of abnormal fetal brain images, show that compared to the original algorithm, the coarse-to-fine strategy reaches higher performance and yields template images that preserve important details while avoiding unrealistic features

Appendiceal intussusception caused by a mucocele of the appendix: imaging findings.

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Calcified aneurysm of the abdominal aorta 12 years after umbilical artery catheterization.

International audienceWe report a 12-year-old boy who presented with abdominal pain and who was found to have an aneurysm of the abdominal aorta (AAA). The patient was born from a quadruplet pregnancy induced by in vitro fertilization. Postnatal transient respiratory distress required assisted ventilation that had been monitored by two consecutive umbilical arterial catheters (UAC). AAA is a rare condition in childhood. Infection and/or trauma are known to be the most frequent causes. Most of the reported cases have occurred in children in whom a UAC had been placed during the neonatal period. In this patient the delay between UAC placement and diagnosis was considerable. At the time of this report the patient had remained well during a follow-up of 8 years after treatment

Patterns of Detection of Fetal Posterior Fossa Anomalies: Analysis of 81 Cases in the Second Half of Gestation

&lt;b&gt;&lt;i&gt;Objective:&lt;/i&gt;&lt;/b&gt; To establish which characteristics of fetal ultrasound screening lead to the diagnosis of posterior fossa (PF) anomalies. &lt;b&gt;&lt;i&gt;Methods:&lt;/i&gt;&lt;/b&gt; A total of 81 fetuses with PF anomalies diagnosed after dedicated neuroimaging between July 1, 2007, and January 1, 2013, were included. The ultrasound characteristics of the fetal cerebellum categorized according to an anatomical approach to the PF, associated fetal anomalies, gestational age at diagnosis, and the potential benefits from systematic measurement of the transverse cerebellar diameter (TCD) were analyzed. &lt;b&gt;&lt;i&gt;Results:&lt;/i&gt;&lt;/b&gt; Fifty fetuses (61.7%) presented with a PF malformation responsible for an increased “fluid-filled” space of the PF, 24 fetuses (29.6%) had a malformation associated with a decreased cerebellar biometry, 23 fetuses (28.4%) had an abnormal cerebellar anatomy and/or echogenicity, and 2 fetuses (2.4%) showed an isolated malformation of the brainstem. Forty-seven cases (58%) showed additional cerebral or extracerebral anomalies, which led to the diagnosis of PF anomaly in 55.3% of the cases. Isolated PF anomalies were associated with an increased “fluid-filled” space of the PF in 91.2% of the cases. Twenty-eight fetuses had a TCD measurement considered as pathological. &lt;b&gt;&lt;i&gt;Discussion:&lt;/i&gt;&lt;/b&gt; Examination of the transcerebellar plane during 2nd- and 3rd-trimester ultrasound screening combined with systematic measurement of the TCD would allow improving the detection of PF anomalies.</jats:p

Contribution of CT and MRI in the analysis of fetal craniofacial malformations

International audienceA wide range of craniofacial malformations can be diagnosed in utero using ultrasonography. However, even in the best hands and conditions of examination, some anatomical structures cannot be properly analyzed by this technique. The aim of this pictorial essay is to show the additional value of fetal Magnetic Resonance Imaging and Computed Tomography in this setting and to illustrate the role of these modalities in various craniofacial malformations: craniosynostosis, facial clefts, ear, eye and nose abnormalities, otomandibular dysplasias and facial cephaloceles

[Functional MR urography in children]

International audienceMR Urography (MRU) provides both morphologic and functional information without radiation exposure. It enables the assessment of split renal function, excretion, and quantification of obstruction. MRU is thus complementary to ultrasonography in the assessment of pre- and post-natal obstructive uropathies in children. If available, MRU should be definitely preferred to intravenous urography