HYR2PICS: Hybrid Regularized Reconstruction for combined Parallel Imaging and Compressive Sensing in MRI

International audienceBoth parallel Magnetic Resonance Imaging~(pMRI) and Compressed Sensing (CS) are emerging techniques to accelerate conventional MRI by reducing the number of acquired data in the $k$-space. So far, first attempts to combine sensitivity encoding (SENSE) imaging in pMRI with CS have been proposed in the context of Cartesian trajectories. Here, we extend these approaches to non-Cartesian trajectories by jointly formulating the CS and SENSE recovery in a hybrid Fourier/wavelet framework and optimizing a convex but nonsmooth criterion. On anatomical MRI data, we show that HYR$^2$PICS outperforms wavelet-based regularized SENSE reconstruction. Our results are also in agreement with the Transform Point Spread Function (TPSF) criterion that measures the degree of incoherence of $k$-space undersampling schemes

AGuIX® from bench to bedside-Transfer of an ultrasmall theranostic gadolinium-based nanoparticle to clinical medicine

International audienceAGuIX® are sub-5 nm nanoparticles made of a polysiloxane matrix and gadolinium chelates. This nanoparticle has been recently accepted in clinical trials in association with radiotherapy. This review will summarize the principal preclinical results that have led to first in man administration. No evidence of toxicity has been observed during regulatory toxicity tests on two animal species (rodents and monkeys). Biodistributions on different animal models have shown passive uptake in tumours due to enhanced permeability and retention effect combined with renal elimination of the nanoparticles after intravenous administration. High radiosensitizing effect has been observed with different types of irradiations in vitro and in vivo on a large number of cancer types (brain, lung, melanoma, head and neck…). The review concludes with the second generation of AGuIX nanoparticles and the first preliminary results on human

Fast reproducible identification and large-scale databasing of individual functional cognitive networks

<p>Abstract</p> <p>Background</p> <p>Although cognitive processes such as reading and calculation are associated with reproducible cerebral networks, inter-individual variability is considerable. Understanding the origins of this variability will require the elaboration of large multimodal databases compiling behavioral, anatomical, genetic and functional neuroimaging data over hundreds of subjects. With this goal in mind, we designed a simple and fast acquisition procedure based on a 5-minute functional magnetic resonance imaging (fMRI) sequence that can be run as easily and as systematically as an anatomical scan, and is therefore used in every subject undergoing fMRI in our laboratory. This protocol captures the cerebral bases of auditory and visual perception, motor actions, reading, language comprehension and mental calculation at an individual level.</p> <p>Results</p> <p>81 subjects were successfully scanned. Before describing inter-individual variability, we demonstrated in the present study the reliability of individual functional data obtained with this short protocol. Considering the anatomical variability, we then needed to correctly describe individual functional networks in a voxel-free space. We applied then non-voxel based methods that automatically extract main features of individual patterns of activation: group analyses performed on these individual data not only converge to those reported with a more conventional voxel-based random effect analysis, but also keep information concerning variance in location and degrees of activation across subjects.</p> <p>Conclusion</p> <p>This collection of individual fMRI data will help to describe the cerebral inter-subject variability of the correlates of some language, calculation and sensorimotor tasks. In association with demographic, anatomical, behavioral and genetic data, this protocol will serve as the cornerstone to establish a hybrid database of hundreds of subjects suitable to study the range and causes of variation in the cerebral bases of numerous mental processes.</p

Diagnostique d'homogénéité et inférence non-paramétrique pour l'analyse de groupe en imagerie par résonance magnétique fonctionnelle

L'un des objectifs principaux de l'imagerie par résonance magnétique fonctionnelle (IRMf) est la localisation in vivo et de manière non invasive des zones cérébrales associées à certaines fonctions cognitives. Le cerveau présentant une très grande variabilité anatomo-fonctionnelle inter-individuelle, les études d'IRMf incluent généralement plusieurs sujets et une analyse de groupe permet de résumer les résultats intra-sujets en une carte d'activation du groupe représentative de la population d'intérêt. L'analyse de groupe standard repose sur une hypothèse forte d'homogénéité des effets estimés à travers les sujets. Dans un premier temps, nous étudions la validité de cette hypothèse par une méthode multivariée diagnostique et un test de normalité univarié (le test de Grubbs). L'application de ces méthodes sur une vingtaine de jeux de données révèle la présence fréquente de données atypiques qui peuvent invalider l'hypothèse d'homogénéité. Nous proposons alors d'utiliser des statistiques de décision robustes calibrées par permutations afin d'améliorer la spécificité et la sensibilité des tests statistiques pour l'analyse de groupe. Puis nous introduisons de nouvelles statistiques de décision à effets mixtes fondées sur le rapport de vraisemblances maximales, permettant de pondérer les sujets en fonction de l'incertitude sur l'estimation de leurs effets. Nous confirmons sur des jeux de données que ces nouvelles méthodes d'inférence permettent un gain en sensibilité significatif, et nous fournissons l'ensemble des outils développés lors de cette thèse à la communauté de neuro-imagerie dans le logiciel DISTANCE.One of the most challenging purposes to reach for the functional magnetic resonance imaging (fMRI) is the in vivo and non invasive localization of cerebral areas involved in some cognitive functions. Due to the high degree of anatomo-functional variability observed for human brains, fMRI studies generally involve several subjects, which results are summarized into a group activation map representing the population of interest through a group analysis procedure. The standard procedure for group analysis inference relies on the strong assumption that the estimated effects are normally distributed across subjects. Our first concern is to study the validity of this assumption using both a multivariate diagnosis approach and a univariate normality test (the Grubbs test). These methods are tested on twenty datasets revealing that the homogeneity assumption may be violated by the frequent presence of atypical data. To enhance both sensibility and sensitivity of statistical tests used for group analysis, we then propose to use robust decision statistics calibrated through permutation testing methods. We also introduce new mixed effects statistics based on maximum likelihoods ratio, which allow to re-weight the subjects according to the reliability of their respective effect estimates. The results obtained on several datasets confirm a significant enhancement of sensibility in group activations maps. We therefore propose all our group analysis methods to the neuro-imaging community through our DISTANCE software.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Syntax production in bilinguals.

International audienceWe used fMRI to examine the functional correlates of syntactical processing in the first (L1) and second (L2) languages of non-proficient, late bilinguals. Subjects either covertly read words or produced sentences from them. Syntactical production during sentence production activated regions including left inferior frontal (LIFG) gyrus and the supplementary motor area in both languages. Analyses performed on the LIFG activation identified on a subject-by-subject basis revealed greater activation in L2 compared to L1 during sentence production and during word reading, consistent with previous work suggesting that greater cognitive effort may be subserved by less well-tuned neural representations that require greater neuronal activity. Remarkably, there was a greater separation in the LIFG activations in L1 versus L2 in less compared to more proficient bilinguals during syntax production, suggesting a functional reorganisation of regions involved in syntactical production as a function of syntactical proficiency

Syntax production in bilinguals

We used fMRI to examine the functional correlates of syntactical processing in the first (L1) and second (L2) languages of non-proficient, late bilinguals. Subjects either covertly read words or produced sentences from them. Syntactical production during sentence production activated regions including left inferior frontal (LIFG) gyrus and the supplementary motor area in both languages. Analyses performed on the LIFG activation identified on a subject-by-subject basis revealed greater activation in L2 compared to L1 during sentence production and during word reading, consistent with previous work suggesting that greater cognitive effort may be subserved by less well-tuned neural representations that require greater neuronal activity. Remarkably, there was a greater separation in the LIFG activations in L1 versus L2 in less compared to more proficient bilinguals during syntax production, suggesting a functional reorganisation of regions involved in syntactical production as a function of syntactical proficiency. © 2005 Elsevier Ltd. All rights reserved

MR imaging of theranostic Gd-based Aguix nanoparticles in patients with 4 histological types of brain metastasis

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Characterization of the diffusion process of different Gadolinium-based nanoparticles within the brain tissue after ultrasound induced Blood-Brain Barrier permeabilization

International audienceWe present here a new method to study the diffusion process of Gadolinium-based MRI Contrast Agents within the brain extracellular space after ultrasound-induced Blood-Brain Barrier permeabilization. Four compounds were tested (MultiHance, Gadovist, Dotarem and AGuIX). By estimating the Free Diffusion Coefficients from in vitro studies, and the Apparent Diffusion Coefficients from in vivo experiments, an evaluation of the tortuosity (λ) in the right striatum of 11 Sprague-Dawley rats has been performed. The values of λ are in agreement with literature and demonstrate that the chosen permeabilization protocol maintains the integrity of brain tissue

MR imaging of theranostic Gd-based Aguix nanoparticles in patients with 4 histological types of brain metastasis

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