Simultaneous pressure-volume measurements using optical sensors and MRI 1 for left ventricle function assessment during animal experiment 2

International audienceSimultaneous pressure and volume measurements enable the extraction of valuable parameters for left ventricle function assessment. Cardiac MR has proven to be the most accurate method for volume estimation. Nonetheless, measuring pressure simultaneously during MRI acquisitions remains a challenge given the magnetic nature of the widely used pressure transducers. In this study we show the feasibility of simultaneous in vivo pressure-volume acquisitions with MRI using optical pressure sensors. Pressure-volume loops were calculated while inducing three inotropic states in a sheep and functional indices were extracted, using single beat loops, to characterize systolic and diastolic performance. Functional indices evolved as expected in response to positive inotropic stimuli. The end-systolic elastance, representing the contractility index, the diastolic myocardium compliance, and the cardiac work efficiency all increased when inducing inotropic state enhancement. The association of MRI and optical pressure sensors within the left ventricle successfully enabled pressure-volume loop analysis after having respective data simultaneously recorded during the experimentation without the need to move the animal between each inotropic state

Comparison of fast field-cycling magnetic resonance imaging methods and future perspectives

This article is based upon work from COST Action CA15209, supported by COST (European Cooperation in Science and Technology). M. Bödenler, C. Gösweiner and H. Scharfetter acknowledge the financial support by the European Commission in the frame of the H2020 Future and Emerging Technologies (FET-open) under grant agreement 665172, project ‘CONQUER’. L. de Rochefort acknowledges the France Life Imaging network (Grant ANR-11-INBS-0006) that partially funded the small animal FFC-MRI system. D.J. Lurie, L.M. Broche and P.J. Ross acknowledge funding from the European Union’s H2020 research and innovation programme under grant agreement No 668119, project ‘IDentIFY’.Peer reviewedPublisher PD

Molecular Magnetic Resonance and Ultrasound Imaging of Tumor Angiogenesis

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Evaluation of lung recovery after static administration of three different perfluorocarbons in pigs.

International audienceBackground: The respiratory properties of perfluorocarbons (PFC) have been widely studied for liquid ventilation inhumans and animals. Several PFC were tested but their tolerance may depend on the species. Here, the effects of asingle administration of liquid PFC into pig lungs were assessed and compared. Three different PFC having distinctevaporative and spreading coefficient properties were evaluated (Perfluorooctyl bromide [PFOB], perfluorodecalin[PFD] and perfluoro-N-octane [PFOC]).Methods: Pigs were anesthetized and submitted to mechanical ventilation. They randomly received an intra-trachealadministration of 15 ml/kg of either PFOB, PFD or PFOC with 12 h of mechanical ventilation before awakening andweaning from ventilation. A Control group was submitted to mechanical ventilation with no PFC administration. Allanimals were followed during 4 days after the initial PFC administration to investigate gas exchanges and clinicalrecovery. They were ultimately euthanized for histological analyses and assessment of PFC residual concentrationswithin the lungs using dual nuclei fluorine and hydrogen Magnetic Resonance Imaging (MRI). Sixteen animals wereincluded (4/group).Results: In the PFD group, animals tended to be hypoxemic after awakening. In PFOB and PFOC groups, blood gaseswere not significantly different from the Control group after awakening. The poor tolerance of PFD was likely related toa large amount of residual PFC, as observed using MRI in all lung samples (≈10% of lung volume). This percentage waslower in the PFOB group (≈1%) but remained significantly greater than in the Control group. In the PFOC group, thepercentage of residual PFC was not significantly different from that of the Control group (≈0.1%). Histologically, themost striking feature was an alveolar infiltration with foam macrophages, especially in the groups treated by PFD orPFOB.Conclusions: Of the three tested perfluorocarbons, PFOC offered the best tolerance in terms of lung function, gasexchanges and residuum in the lung. PFOC was rapidly cleared from the lungs and virtually disappeared after 4 dayswhereas PFOB persisted at significant levels and led to foam macrophage infiltration. PFOC could be relevant for shortterm total liquid ventilation with a rapid weaning

European Ultrahigh-Field Imaging Network for Neurodegenerative Diseases (EUFIND).

INTRODUCTION: The goal of European Ultrahigh-Field Imaging Network in Neurodegenerative Diseases (EUFIND) is to identify opportunities and challenges of 7 Tesla (7T) MRI for clinical and research applications in neurodegeneration. EUFIND comprises 22 European and one US site, including over 50 MRI and dementia experts as well as neuroscientists. METHODS: EUFIND combined consensus workshops and data sharing for multisite analysis, focusing on 7 core topics: clinical applications/clinical research, highest resolution anatomy, functional imaging, vascular systems/vascular pathology, iron mapping and neuropathology detection, spectroscopy, and quality assurance. Across these topics, EUFIND considered standard operating procedures, safety, and multivendor harmonization. RESULTS: The clinical and research opportunities and challenges of 7T MRI in each subtopic are set out as a roadmap. Specific MRI sequences for each subtopic were implemented in a pilot study presented in this report. Results show that a large multisite 7T imaging network with highly advanced and harmonized imaging sequences is feasible and may enable future multicentre ultrahigh-field MRI studies and clinical trials. DISCUSSION: The EUFIND network can be a major driver for advancing clinical neuroimaging research using 7T and for identifying use-cases for clinical applications in neurodegeneration

Imagerie dynamique et vélocimétrie IRM des gaz hyperpolarisés

This work is part of a French project called R-MOD that aims at the development of a morpho-functional simulator of the upper and central airways. Here, hyperpolarized gas (HPG) MRI methods to visualize and quantify gas flows were developed to test the predictions of the simulator.To reach this goal, a dedicated MR-compatible device was built to administrate HPG in a controlled way and different imaging strategies were evaluated.A first qualitative approach was based on dynamic imaging of a HPG inspiration. An analysis of this type of experiment was achieved. The temporal evolution of the phenomenon is too high to be correctly imaged with the state-of-the-art techniques. Nevertheless, spatial distribution of the magnetization within the lung reaches an equilibrium state during a stationary inspiration. This equilibrium state depends on parameters that were explored both theoretically and experimentally through several dynamic imaging techniques.A second approach, more quantitative, is based on phase-contrast velocimetry combined with rapid radial imaging. The technique was first validated on known flow patterns (straight, curved and bifurcating pipes) and then applied on a realistic bronchial tree reconstructed from medical images and compared to computational fluid dynamics simulations. The 3 velocity components were measured within about 1 s, with 1-mm spatial resolution, and a precision of 1cm•s-1. Finally, in vivo feasibility was shown on a human trachea during an inhalation.This flow characterization technique based on HPG MRI is a promising tool for fluid dynamics studies and for related medical applications.Ce travail s'inscrit dans le cadre du projet RNTS R-MOD qui visait le développement d'un simulateur morpho-fonctionnel des voies respiratoires. Des méthodes de visualisation et de quantification de flux gazeux pulmonaires par IRM des gaz hyperpolarisés (GHP) ont été développées pour pouvoir valider les résultats du simulateur.Pour atteindre cet objectif, un système adapté à l'environnement spécifique de l'IRM a été développé pour permettre l'administration de GHP de manière contrôlée, et différentes approches d'imagerie du flux de GHP ont été explorées.La 1ère approche est basée sur de l'imagerie dynamique de l'inspiration de GHP. Ce type d'expérience est analysé. L'évolution du phénomène est trop rapide pour être observée correctement avec les techniques actuelles. Néanmoins, un état d'équilibre dynamique de la répartition spatiale de l'aimantation dans les poumons lors d'inspirations en régime stationnaire est observable. Les paramètres dont dépend cet équilibre et une partie de ce qui peut être quantifié par le biais de ce type d'expérience ont été formalisés et les concepts introduits ont été validés par différentes expériences d'imagerie dynamique.La 2ième approche, quantitative, est basée sur la vélocimétrie par contraste de phase combinée à l'imagerie radiale rapide. D'abord validée quantitativement sur des fantômes d'écoulement connus (tube droit, coude, bifurcation), la technique a ensuite été appliquée sur un modèle réaliste d'arbre bronchique et comparée à une simulation numérique des écoulements. Les 3 composantes de la vitesse ont été mesurées en environ 1 s avec une résolution spatiale du mm et une précision du cm•s-1. Enfin, la faisabilité in vivo de la mesure de vitesse dans les voies aériennes pulmonaires a été démontrée dans la trachée lors d'une inspiration.Cet outil de caractérisation des écoulements à l'aide de l'IRM des GHP ouvre des voies prometteuses aussi bien pour la physique des écoulements que pour les applications médicales

Imagerie dynamique et vélocimétrie IRM des gaz hyperpolarisés

This work is part of a French project called R-MOD that aims at the development of a morpho-functional simulator of the upper and central airways. Here, hyperpolarized gas (HPG) MRI methods to visualize and quantify gas flows were developed to test the predictions of the simulator.To reach this goal, a dedicated MR-compatible device was built to administrate HPG in a controlled way and different imaging strategies were evaluated.A first qualitative approach was based on dynamic imaging of a HPG inspiration. An analysis of this type of experiment was achieved. The temporal evolution of the phenomenon is too high to be correctly imaged with the state-of-the-art techniques. Nevertheless, spatial distribution of the magnetization within the lung reaches an equilibrium state during a stationary inspiration. This equilibrium state depends on parameters that were explored both theoretically and experimentally through several dynamic imaging techniques.A second approach, more quantitative, is based on phase-contrast velocimetry combined with rapid radial imaging. The technique was first validated on known flow patterns (straight, curved and bifurcating pipes) and then applied on a realistic bronchial tree reconstructed from medical images and compared to computational fluid dynamics simulations. The 3 velocity components were measured within about 1 s, with 1-mm spatial resolution, and a precision of 1cm•s-1. Finally, in vivo feasibility was shown on a human trachea during an inhalation.This flow characterization technique based on HPG MRI is a promising tool for fluid dynamics studies and for related medical applications.Ce travail s'inscrit dans le cadre du projet RNTS R-MOD qui visait le développement d'un simulateur morpho-fonctionnel des voies respiratoires. Des méthodes de visualisation et de quantification de flux gazeux pulmonaires par IRM des gaz hyperpolarisés (GHP) ont été développées pour pouvoir valider les résultats du simulateur.Pour atteindre cet objectif, un système adapté à l'environnement spécifique de l'IRM a été développé pour permettre l'administration de GHP de manière contrôlée, et différentes approches d'imagerie du flux de GHP ont été explorées.La 1ère approche est basée sur de l'imagerie dynamique de l'inspiration de GHP. Ce type d'expérience est analysé. L'évolution du phénomène est trop rapide pour être observée correctement avec les techniques actuelles. Néanmoins, un état d'équilibre dynamique de la répartition spatiale de l'aimantation dans les poumons lors d'inspirations en régime stationnaire est observable. Les paramètres dont dépend cet équilibre et une partie de ce qui peut être quantifié par le biais de ce type d'expérience ont été formalisés et les concepts introduits ont été validés par différentes expériences d'imagerie dynamique.La 2ième approche, quantitative, est basée sur la vélocimétrie par contraste de phase combinée à l'imagerie radiale rapide. D'abord validée quantitativement sur des fantômes d'écoulement connus (tube droit, coude, bifurcation), la technique a ensuite été appliquée sur un modèle réaliste d'arbre bronchique et comparée à une simulation numérique des écoulements. Les 3 composantes de la vitesse ont été mesurées en environ 1 s avec une résolution spatiale du mm et une précision du cm•s-1. Enfin, la faisabilité in vivo de la mesure de vitesse dans les voies aériennes pulmonaires a été démontrée dans la trachée lors d'une inspiration.Cet outil de caractérisation des écoulements à l'aide de l'IRM des GHP ouvre des voies prometteuses aussi bien pour la physique des écoulements que pour les applications médicales

Imagerie dynamique et vélocimétrie IRM des gaz hyperpolarisés

Ce travail s'inscrit dans le cadre du projet RNTS R-MOD qui visait le développement d'un simulateur morpho-fonctionnel des voies respiratoires. Des méthodes de visualisation et de quantification de flux gazeux pulmonaires par IRM des gaz hyperpolarisés (GHP) ont été développées pour pouvoir valider les résultats du simulateur.Pour atteindre cet objectif, un système adapté à l'environnement spécifique de l'IRM a été développé pour permettre l'administration de GHP de manière contrôlée, et différentes approches d'imagerie du flux de GHP ont été explorées.La 1ère approche est basée sur de l'imagerie dynamique de l'inspiration de GHP. Ce type d'expérience est analysé. L'évolution du phénomène est trop rapide pour être observée correctement avec les techniques actuelles. Néanmoins, un état d'équilibre dynamique de la répartition spatiale de l'aimantation dans les poumons lors d'inspirations en régime stationnaire est observable. Les paramètres dont dépend cet équilibre et une partie de ce qui peut être quantifié par le biais de ce type d'expérience ont été formalisés et les concepts introduits ont été validés par différentes expériences d'imagerie dynamique.La 2ième approche, quantitative, est basée sur la vélocimétrie par contraste de phase combinée à l'imagerie radiale rapide. D'abord validée quantitativement sur des fantômes d'écoulement connus (tube droit, coude, bifurcation), la technique a ensuite été appliquée sur un modèle réaliste d'arbre bronchique et comparée à une simulation numérique des écoulements. Les 3 composantes de la vitesse ont été mesurées en environ 1 s avec une résolution spatiale du mm et une précision du cm·s-1. Enfin, la faisabilité in vivo de la mesure de vitesse dans les voies aériennes pulmonaires a été démontrée dans la trachée lors d'une inspiration.Cet outil de caractérisation des écoulements à l'aide de l'IRM des GHP ouvre des voies prometteuses aussi bien pour la physique des écoulements que pour les applications médicales.This work is part of a French project called R-MOD that aims at the development of a morpho-functional simulator of the upper and central airways. Here, hyperpolarized gas (HPG) MRI methods to visualize and quantify gas flows were developed to test the predictions of the simulator.To reach this goal, a dedicated MR-compatible device was built to administrate HPG in a controlled way and different imaging strategies were evaluated.A first qualitative approach was based on dynamic imaging of a HPG inspiration. An analysis of this type of experiment was achieved. The temporal evolution of the phenomenon is too high to be correctly imaged with the state-of-the-art techniques. Nevertheless, spatial distribution of the magnetization within the lung reaches an equilibrium state during a stationary inspiration. This equilibrium state depends on parameters that were explored both theoretically and experimentally through several dynamic imaging techniques.A second approach, more quantitative, is based on phase-contrast velocimetry combined with rapid radial imaging. The technique was first validated on known flow patterns (straight, curved and bifurcating pipes) and then applied on a realistic bronchial tree reconstructed from medical images and compared to computational fluid dynamics simulations. The 3 velocity components were measured within about 1 s, with 1-mm spatial resolution, and a precision of 1cm·s-1. Finally, in vivo feasibility was shown on a human trachea during an inhalation.This flow characterization technique based on HPG MRI is a promising tool for fluid dynamics studies and for related medical applications.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

SANGRIA: one-Shot leArNinG super-ResolutIon with Adversarial training for accelerated Magnetic Resonance Imaging

International audienceMagnetic Resonance Imaging (MRI) acquisition is performed sequentially in the spatial-frequency domain (kspace) and involves several views of the object/subject. To accelerate the acquisition, k-space lines are often undersampled on a cartesian grid. Parallel imaging reconstruction algorithms are then applied to recover unseen lines. We consider this super-resolution problem in k-space to further reduce the acquisition time with deep learning and to reduce the costs associated with this expensive medical imaging technology. Because the sensors are specific to anatomical regions and experimental setups, it pushes toward learning a reconstruction model on a per-image basis, i.e. for every scan and image. Here, we propose an extension of state-of-the-art MRI reconstruction methods where the super-resolution task in k-space is solved with a convolutional neural network, and where an adversarial strategy using a patch discriminator in image space is used to reach higher undersampling rates. Both parts are trained in a one-shot learning setting. It is demonstrated both using simulated and in vivo brain experiments that this combined approach provides enhanced image quality for undersampling rates larger than the ones used in a clinical routine on multi-slice 2D T2-weighted imaging sequences, making the approach readily applicable as an alternative reconstruction strategy in MRI systems for 2D parallel imaging, and which could be further extended to accelerate 3D imaging sequences

Accelerating Phase and Quantitative susceptibility mapping with Scan-Specific Complex Convolutional Neural Networks

International audienceMRI data is inherently complex-valued, the vast majority of deep learning frameworks do not yet support complex-valued data. Most reconstruction networks separate real and imaginary components into two separate real-valued channels, which may not be the most efficient way to represent complex numbers. Phase is essential for many MRI applications, including phase contrast velocity mapping and Quantitative Susceptibility Mapping (QSM) etc. We propose a new crRAKI, a scan-specific complex-valued residual convolutional neural network for 2D/3D MRI data for accelerating phase mapping and QSM. A comparison is made with GRAPPA and rRAKI for the accelerated reconstruction of MRI images