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1. Human brain representations of internally generated outcomes of approximate calculation revealed by ultra-high-field brain imaging

Author: Sébastien Czajko, Alexandre Vignaud, and Evelyn Eger
Subjects: Science
Abstract: Abstract Much of human culture’s advanced technology owes its existence to the ability to mentally manipulate quantities. Neuroscience has described the brain regions overall recruited by numerical tasks and the neuronal codes representing individual quantities during perceptual tasks. Nevertheless, it remains unknown how quantity representations are combined or transformed during mental computations and how specific quantities are coded in the brain when generated as the result of internal computations rather than evoked by a stimulus. Here, we imaged the brains of adult human subjects at 7 Tesla during an approximate calculation task designed to disentangle in- and outputs of the computation from the operation itself. While physically presented sample numerosities were distinguished in activity patterns along the dorsal visual pathway and within frontal and occipito-temporal regions, a representation of the internally generated result was most prominently detected in higher order regions such as angular gyrus and lateral prefrontal cortex. Behavioral precision in the task was related to cross-decoding performance between sample and result representations in medial IPS regions. This suggests the transformation of sample into result may be carried out within dorsal stream sensory-motor integration regions, and resulting outputs maintained for task purposes in higher-level regions in a format possibly detached from sensory-evoked inputs.
Published: 2024
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2. Non-Cartesian 3D-SPARKLING vs Cartesian 3D-EPI encoding schemes for functional Magnetic Resonance Imaging at 7 Tesla

Author: Zaineb Amor, Philippe Ciuciu, Chaithya G. R., Guillaume Daval-Frérot, Franck Mauconduit, Bertrand Thirion, and Alexandre Vignaud
Subjects: Medicine, Science
Published: 2024

3. Shim coils tailored for correcting B0 inhomogeneity in the human brain (SCOTCH): Design methodology and 48-channel prototype assessment in 7-Tesla MRI

Author: Bruno Pinho Meneses, Jason P. Stockmann, Nicolas Arango, Paul-François Gapais, Eric Giacomini, Franck Mauconduit, Vincent Gras, Nicolas Boulant, Alexandre Vignaud, Michel Luong, and Alexis Amadon
Subjects: B0 Shimming, Human brain shimming, Solid harmonics, Spherical harmonics, Ultra high field, Shim coil design, Neurosciences. Biological psychiatry. Neuropsychiatry, RC321-571
Abstract: Increased static field inhomogeneities are a burden for human brain MRI at Ultra-High-Field. In particular they cause enhanced Echo-Planar image distortions and signal losses due to magnetic susceptibility gradients at air-tissue interfaces in the subject’s head. In the past decade, Multi-Coil Arrays (MCA) have been proposed to shim the field in the brain better than the 2nd or 3rd order Spherical Harmonic (SH) coils usually offered by MRI manufacturers. Here we present a novel MCA, named SCOTCH, optimized for whole brain shimming. Based on a cylindrical structure, it features several layers of small coils whose shape, size and location are found from a principal component analysis of ideal stream functions computed from an internal 100-brain fieldmap database. From an Open-Access external database of 126 brains, our SCOTCH implementation is shown to be equivalent to a partial 7th-order SH system with unlimited power, outperforming all known existing MCA prototypes. This result is further confirmed by a low-cost 30-cm diameter SCOTCH prototype built with 48 coils on 3 layers, and tested on 7 volunteers at 7T with a parallel-transmit RF coil made to be inserted in SCOTCH. Echo-Planar images of the subject brains before and after SCOTCH shimming show large signal recoveries, especially in the prefrontal cortex.
Published: 2022
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4. Imaging the aging brain: study design and baseline findings of the SENIOR cohort

Author: Alexa Haeger, Jean-François Mangin, Alexandre Vignaud, Cyril Poupon, Antoine Grigis, Fawzi Boumezbeur, Vincent Frouin, Jean-Robert Deverre, Marie Sarazin, Lucie Hertz-Pannier, Michel Bottlaender, and the SENIOR team
Subjects: Aging, Imaging, Neurodegenerative disease, Biomarker, Prevention, Cognitive decline, Neurosciences. Biological psychiatry. Neuropsychiatry, RC321-571, Neurology. Diseases of the nervous system, RC346-429
Abstract: Abstract Background Current demographic trends point towards an aging society entailing increasing occurrence and burden of neurodegenerative diseases. In this context, understanding physiological aging and its turning point into neurodegeneration is essential for the development of possible biomarkers and future therapeutics of brain disease. Methods The SENIOR study represents a longitudinal, observational study including cognitively healthy elderlies aged between 50 and 70 years old at the time of inclusion, being followed annually over 10 years. Our multimodal protocol includes structural, diffusion, functional, and sodium magnetic resonance imaging (MRI) at 3 T and 7 T, positron emission tomography (PET), blood samples, genetics, audiometry, and neuropsychological and neurological examinations as well as assessment of neuronal risk factors. Results One hundred forty-two participants (50% females) were enrolled in the SENIOR cohort with a mean age of 60 (SD 6.3) years at baseline. Baseline results with multiple regression analyses reveal that cerebral white matter lesions can be predicted by cardiovascular and cognitive risk factors and age. Cardiovascular risk factors were strongly associated with juxtacortical and periventricular lesions. Intra-subject across-test variability as a measure of neuropsychological test performance and possible cognitive marker predicts white matter volume and is significantly associated with risk profile. Division of the cohort into subjects with a higher and lower risk profile shows significant differences in intra-subject across-test variability and volumes as well as cortical thickness of brain regions of the temporal lobe. There is no difference between the lower- and higher-risk groups in amyloid load using PET data from a subset of 81 subjects. Conclusions We here describe the study protocol and baseline findings of the SENIOR observational study which aim is the establishment of integrated, multiparametric maps of normal aging and the identification of early biomarkers for neurodegeneration. We show that intra-subject across-test variability as a marker of neuropsychological test performance as well as age, gender, and combined risk factors influence neuronal decline as represented by decrease in brain volume, cortical thickness, and increase in white matter lesions. Baseline findings will be used as underlying basis for the further implications of aging and neuronal degeneration as well as examination of brain aging under different aspects of brain pathology versus physiological aging.
Published: 2020
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5. European Ultrahigh‐Field Imaging Network for Neurodegenerative Diseases (EUFIND)

Author: Emrah Düzel, Julio Acosta‐Cabronero, David Berron, Geert Jan Biessels, Isabella Björkman‐Burtscher, Michel Bottlaender, Richard Bowtell, Mark v Buchem, Arturo Cardenas‐Blanco, Fawzi Boumezbeur, Dennis Chan, Stuart Clare, Mauro Costagli, Ludovic deRochefort, Ariane Fillmer, Penny Gowland, Oskar Hansson, Jeroen Hendrikse, Oliver Kraff, Mark E. Ladd, Itamar Ronen, Esben Petersen, James B. Rowe, Hartwig Siebner, Tony Stoecker, Sina Straub, Michela Tosetti, Kamil Uludag, Alexandre Vignaud, Jaco Zwanenburg, and Oliver Speck
Subjects: Magnetic resonance imaging (MRI), Ultrahigh‐field MRI, Alzheimer's disease (AD), Subjective cognitive decline (SCD), Mild cognitive impairment (MCI), Parkinson's disease (PD), Neurology. Diseases of the nervous system, RC346-429, Geriatrics, RC952-954.6
Abstract: Abstract 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.
Published: 2019
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6. Temporal SNR optimization through RF coil combination in fMRI: The more, the better?

Author: Redouane Jamil, Franck Mauconduit, Caroline Le Ster, Philipp Ehses, Benedikt A. Poser, Alexandre Vignaud, and Nicolas Boulant
Subjects: Medicine, Science
Abstract: For functional MRI with a multi-channel receiver RF coil, images are often reconstructed channel by channel, resulting into multiple images per time frame. The final image to analyze usually is the result of the covariance Sum-of-Squares (covSoS) combination across these channels. Although this reconstruction is quasi-optimal in SNR, it is not necessarily the case in terms of temporal SNR (tSNR) of the time series, which is yet a more relevant metric for fMRI data quality. In this work, we investigated tSNR optimality through voxel-wise RF coil combination and its effects on BOLD sensitivity. An analytical solution for an optimal RF coil combination is described, which is somewhat tied to the extended Krueger-Glover model involving both thermal and physiological noise covariance matrices. Compared experimentally to covSOS on four volunteers at 7T, the method yielded great improvement of tSNR but, surprisingly, did not result into higher BOLD sensitivity. Solutions to improve the method such as for example the t-score for the mean recently proposed are also explored, but result into similar observations once the statistics are corrected properly. Overall, the work shows that data-driven RF coil combinations based on tSNR considerations alone should be avoided unless additional and unbiased assumptions can be made.
Published: 2021

7. Mapping subcomponents of numerical cognition in relation to functional and anatomical landmarks of human parietal cortex

Author: Elisa Castaldi, Alexandre Vignaud, and Evelyn Eger
Subjects: 7 Tesla, High resolution fMRI, Number processing, Mathematical cognition, Parietal cortex, Neurosciences. Biological psychiatry. Neuropsychiatry, RC321-571
Abstract: Human functional imaging has identified the middle part of the intraparietal sulcus (IPS) as an important brain substrate for different types of numerical tasks. This area is often equated with the macaque ventral intraparietal area (VIP) where neuronal selectivity for non-symbolic numerical stimuli (sets of items) is found. However, the low spatial resolution and whole-brain averaging analysis performed in most fMRI studies limit the extent to which an exact correspondence of activations in different numerical tasks with specific sub-regions of the IPS can be established. Here we acquired high-resolution 7T fMRI data in a group of human adults and related the activations in several numerical contrasts (implying different numerical stimuli and tasks) to anatomical and functional landmarks on the cortical surface. Our results reveal a functional heterogeneity within human intraparietal cortex where the retinotopic visual field maps in superior/medial parts of the IPS and superior parietal gyrus respond preferentially to the visual processing of concrete sets of items (over single Arabic numerals), whereas lateral/inferior parts of the IPS are predominantly recruited during numerical operations such as calculation and quantitative comparison. Since calculation and comparison-related activity fell mainly outside the retinotopic visual field maps considered the human functional equivalent of the monkey VIP/LIP complex, the areas most activated during such numerical operations in humans are likely different from VIP.
Published: 2020
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8. Attentional amplification of neural codes for number independent of other quantities along the dorsal visual stream

Author: Elisa Castaldi, Manuela Piazza, Stanislas Dehaene, Alexandre Vignaud, and Evelyn Eger
Subjects: 7T fMRI, multivariate decoding, representational similarity analysis, number processing, dorsal visual stream, feature based attention, Medicine, Science, Biology (General), QH301-705.5
Abstract: Humans and other animals base important decisions on estimates of number, and intraparietal cortex is thought to provide a crucial substrate of this ability. However, it remains debated whether an independent neuronal processing mechanism underlies this ‘number sense’, or whether number is instead judged indirectly on the basis of other quantitative features. We performed high-resolution 7 Tesla fMRI while adult human volunteers attended either to the numerosity or an orthogonal dimension (average item size) of visual dot arrays. Along the dorsal visual stream, numerosity explained a significant amount of variance in activation patterns, above and beyond non-numerical dimensions. Its representation was selectively amplified and progressively enhanced across the hierarchy when task relevant. Our results reveal a sensory extraction mechanism yielding information on numerosity separable from other dimensions already at early visual stages and suggest that later regions along the dorsal stream are most important for explicit manipulation of numerical quantity.
Published: 2019
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9. Comparison of SMS-EPI and 3D-EPI at 7T in an fMRI localizer study with matched spatiotemporal resolution and homogenized excitation profiles.

Author: Caroline Le Ster, Antonio Moreno, Franck Mauconduit, Vincent Gras, Ruediger Stirnberg, Benedikt A Poser, Alexandre Vignaud, Evelyn Eger, Stanislas Dehaene, Florent Meyniel, and Nicolas Boulant
Subjects: Medicine, Science
Abstract: The simultaneous multi-slice EPI (SMS-EPI, a.k.a. MB-EPI) sequence has met immense popularity recently in functional neuroimaging. A still less common alternative is the use of 3D-EPI, which offers similar acceleration capabilities. The aim of this work was to compare the SMS-EPI and the 3D-EPI sequences in terms of sampling strategies for the detection of task-evoked activations at 7T using detection theory. To this end, the spatial and temporal resolutions of the sequences were matched (1.6 mm isotropic resolution, TR = 1200 ms) and their excitation profiles were homogenized by means of calibration-free parallel-transmission (Universal Pulses). We used a fast-event "localizer" paradigm of 5:20 min in order to probe sensorimotor functions (visual, auditory and motor tasks) as well as higher level functions (language comprehension, mental calculation), where results from a previous large-scale study at 3T (N = 81) served as ground-truth reference for the brain areas implicated in each cognitive function. In the current study, ten subjects were scanned while their activation maps were generated for each cognitive function with the GLM analysis. The SMS-EPI and 3D-EPI sequences were compared in terms of raw tSNR, t-score testing for the mean signal, activation strength and accuracy of the robust sensorimotor functions. To this end, the sensitivity and specificity of these contrasts were computed by comparing their activation maps to the reference brain areas obtained in the 3T study. Estimated flip angle distributions in the brain reported a normalized root mean square deviation from the target value below 10% for both sequences. The analysis of the t-score testing for the mean signal revealed temporal noise correlations, suggesting the use of this metric instead of the traditional tSNR for testing fMRI sequences. The SMS-EPI and 3D-EPI thereby yielded similar performance from a detection theory perspective.
Published: 2019
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10. Multi-parametric quantitative MRI reveals three different white matter subtypes.

Author: Jack R Foucher, Olivier Mainberger, Julien Lamy, Mathieu D Santin, Alexandre Vignaud, Mathilde M Roser, and Paulo L de Sousa
Subjects: Medicine, Science
Abstract: INTRODUCTION:Magnetic resonance imaging (MRI) shows slight spatial variations in brain white matter (WM). We used quantitative multi-parametric MRI to evaluate in what respect these inhomogeneities could correspond to WM subtypes with specific characteristics and spatial distribution. MATERIALS AND METHODS:Twenty-six controls (12 women, 38 ±9 Y) took part in a 60-min session on a 3T scanner measuring 7 parameters: R1 and R2, diffusion tensor imaging which allowed to measure Axial and Radial Diffusivity (AD, RD), magnetization transfer imaging which enabled to compute the Macromolecular Proton Fraction (MPF), and a susceptibility-weighted sequence which permitted to quantify R2* and magnetic susceptibility (χm). Spatial independent component analysis was used to identify WM subtypes with specific combination of quantitative parameters values. RESULTS:Three subtypes could be identified. t-WM (track) mostly mapped on well-formed projection and commissural tracts and came with high AD values (all p < 10(-18)). The two other subtypes were located in subcortical WM and overlapped with association fibers: f-WM (frontal) was mostly anterior in the frontal lobe whereas c-WM (central) was underneath the central cortex. f-WM and c-WM had higher MPF values, indicating a higher myelin content (all p < 1.7 10(-6)). This was compatible with their larger χm and R2, as iron is essentially stored in oligodendrocytes (all p < 0.01). Although R1 essentially showed the same, its higher value in t-WM relative to c-WM might be related to its higher cholesterol concentration. CONCLUSIONS:Thus, f- and c-WMs were less structured, but more myelinated and probably more metabolically active regarding to their iron content than WM related to fasciculi (t-WM). As known WM bundles passed though different WM subtypes, myelination might not be uniform along the axons but rather follow a spatially consistent regional variability. Future studies might examine the reproducibility of this decomposition and how development and pathology differently affect each subtype.
Published: 2018
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11. Homogeneous non-selective and slice-selective parallel-transmit excitations at 7 Tesla with universal pulses: A validation study on two commercial RF coils.

Author: Vincent Gras, Markus Boland, Alexandre Vignaud, Guillaume Ferrand, Alexis Amadon, Franck Mauconduit, Denis Le Bihan, Tony Stöcker, and Nicolas Boulant
Subjects: Medicine, Science
Abstract: Parallel transmission (pTx) technology, despite its great potential to mitigate the transmit field inhomogeneity problem in magnetic resonance imaging at ultra-high field (UHF), suffers from a cumbersome calibration procedure, thereby making the approach problematic for routine use. The purpose of this work is to demonstrate on two different 7T systems respectively equipped with 8-transmit-channel RF coils from two different suppliers (Rapid-Biomed and Nova Medical), the benefit of so-called universal pulses (UP), optimized to produce uniform excitations in the brain in a population of adults and making unnecessary the calibration procedures mentioned above. Non-selective and slice-selective UPs were designed to return homogeneous excitation profiles throughout the brain simultaneously on a group of ten subjects, which then were subsequently tested on ten additional volunteers in magnetization prepared rapid gradient echo (MPRAGE) and multi-slice gradient echo (2D GRE) protocols. The results were additionally compared experimentally with the standard non-pTx circularly-polarized (CP) mode, and in simulation with subject-specific tailored excitations. For both pulse types and both coils, the UP mode returned a better signal and contrast homogeneity than the CP mode. Retrospective analysis of the flip angle (FA) suggests that the FA deviation from the nominal FA on average over a healthy adult population does not exceed 11% with the calibration-free parallel-transmit pulses whereas it goes beyond 25% with the CP mode. As a result the universal pulses designed in this work confirm their relevance in 3D and 2D protocols with commercially available equipment. Plug-and-play pTx implementations henceforth become accessible to exploit with more flexibility the potential of UHF for brain imaging.
Published: 2017
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12. Detection of volume loss in hippocampal layers in Alzheimer's disease using 7 T MRI: A feasibility study

Author: Claire Boutet, Marie Chupin, Stéphane Lehéricy, Linda Marrakchi-Kacem, Stéphane Epelbaum, Cyril Poupon, Christopher Wiggins, Alexandre Vignaud, Dominique Hasboun, Bénédicte Defontaines, Olivier Hanon, Bruno Dubois, Marie Sarazin, Lucie Hertz-Pannier, and Olivier Colliot
Subjects: Alzheimer's disease, Human 7 T MRI, Hippocampus, Hippocampal layers, Segmentation, Volumetry, Computer applications to medicine. Medical informatics, R858-859.7, Neurology. Diseases of the nervous system, RC346-429
Abstract: In Alzheimer's disease (AD), the hippocampus is an early site of tau pathology and neurodegeneration. Histological studies have shown that lesions are not uniformly distributed within the hippocampus. Moreover, alterations of different hippocampal layers may reflect distinct pathological processes. 7 T MRI dramatically improves the visualization of hippocampal subregions and layers. In this study, we aimed to assess whether 7 T MRI can detect volumetric changes in hippocampal layers in vivo in patients with AD. We studied four AD patients and seven control subjects. MR images were acquired using a whole-body 7 T scanner with an eight channel transmit–receive coil. Hippocampal subregions were manually segmented from coronal T2*-weighted gradient echo images with 0.3 × 0.3 × 1.2 mm3 resolution using a protocol that distinguishes between layers richer or poorer in neuronal bodies. Five subregions were segmented in the region of the hippocampal body: alveus, strata radiatum, lacunosum and moleculare (SRLM) of the cornu Ammonis (CA), hilum, stratum pyramidale of CA and stratum pyramidale of the subiculum. We found strong bilateral reductions in the SRLM of the cornu Ammonis and in the stratum pyramidale of the subiculum (p
Published: 2014
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13. Kerker Effect in Ultrahigh-Field Magnetic Resonance Imaging

Author: Marc Dubois, Lisa Leroi, Zo Raolison, Redha Abdeddaim, Tryfon Antonakakis, Julien de Rosny, Alexandre Vignaud, Pierre Sabouroux, Elodie Georget, Benoit Larrat, Gérard Tayeb, Nicolas Bonod, Alexis Amadon, Franck Mauconduit, Cyril Poupon, Denis Le Bihan, and Stefan Enoch
Subjects: Physics, QC1-999
Abstract: Ultrahigh-field (UHF) magnetic resonance imaging (MRI) systems are getting a lot of attention as they ensure high intrinsic signal-to-noise ratio resulting in higher spatial and temporal resolutions as well as better contrast. This promises improved clinical results with regard to morphological as well as functional and metabolic capabilities. Traditionally, MRI relies on volume coils (birdcage) able to deliver a homogeneous radio frequency field exciting the nuclei magnetic spin. However, this strategy is hindered at UHF because of the rf field inhomogeneities yielded by the increased Larmor frequency. A standard approach consists of inserting passive dielectric elements within the volume coil in order to locally enhance the rf field and mitigate these inhomogeneities. However, the lack of control over their electromagnetic properties prevents the development of optimal solutions. Here, a single meta-atom is used to achieve efficient and tunable rf field control in UHF MRI. We demonstrate theoretically and experimentally a full overlap between the electric dipolar and magnetic dipolar resonances of the meta-atom. This interaction is precisely tuned to reach the so-called Kerker scattering conditions when illuminated in the near field by a birdcage coil. At these conditions, a strong enhancement or suppression of the rf field is achieved in the vicinity of the meta-atom within the MRI volume coil.
Published: 2018
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14. BLOCH equations-based reconstruction of myocardium t1 maps from modified look-locker inversion recovery sequence.

Author: Benjamin Marty, Alexandre Vignaud, Andreas Greiser, Benjamin Robert, Paulo Loureiro de Sousa, and Pierre G Carlier
Subjects: Medicine, Science
Abstract: Modified Look-Locker Inversion recovery (MOLLI) sequence is increasingly performed for myocardial T1 mapping but is known to underestimate T1 values. The aim of the study was to quantitatively analyze several sources of errors when T1 maps are derived using standard post-processing of the sequence and to propose a reconstruction approach that takes into account inversion efficacy (η), T2 relaxation during balanced steady-state free-precession readouts and B1+ inhomogeneities. Contributions of the different sources of error were analyzed using Bloch equations simulations of MOLLI sequence. Bloch simulations were then combined with the acquisition of fast B1+ and T2 maps to derive more accurate T1 maps. This novel approach was evaluated on phantoms and on five healthy volunteers. Simulations show that T2 variations, B1+ heterogeneities and inversion efficiency represent major confounders for T1 mapping when MOLLI is processed with standard 3-parameters fitting. In vitro data indicate that T1 values are accurately derived with the simulation approach and in vivo data suggest that myocardium T1 are 15% underestimated when processed with the standard 3-parameters fitting. At the cost of additional acquisitions, this method might be suitable in clinical research protocols for precise tissue characterization as it decorrelates T1 and T2 effects on parametric maps provided by MOLLI sequence and avoids inaccuracies when B1+ is not homogenous throughout the myocardium.
Published: 2015
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15. In vivo high-resolution 7 Tesla MRI shows early and diffuse cortical alterations in CADASIL.

Author: François De Guio, Sonia Reyes, Alexandre Vignaud, Marco Duering, Stefan Ropele, Edouard Duchesnay, Hugues Chabriat, and Eric Jouvent
Subjects: Medicine, Science
Abstract: 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 ≤1 and Mini Mental State Examination (MMSE) ≥24).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.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.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.
Published: 2014
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16. Denoising of fMRI Volumes Using Local Low Rank Methods.

Author: Pierre-Antoine Comby, Zaineb Amor, Alexandre Vignaud, and Philippe Ciuciu
Published: 2023
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17. Non-Cartesian Non-Fourier FMRI Imaging for High-Resolution Retinotopic Mapping at 7 Tesla.

Author: Zaineb Amor, Pierre-Antoine Comby, Caroline Le Ster, Alexandre Vignaud, and Philippe Ciuciu
Published: 2023
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18. Optimizing Full 3D SPARKLING Trajectories for High-Resolution Magnetic Resonance Imaging.

Author: Chaithya G. R., Pierre Weiss, Guillaume Daval-Frerot, Aurélien Massire, Alexandre Vignaud, and Philippe Ciuciu
Published: 2022
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19. A Diffeomorphic Vector Field Approach to Analyze the Thickness of the Hippocampus From 7 T MRI.

Author: Alexis Guyot, Ana B. Graciano Fouquier, Emilie Gerardin, Marie Chupin, Joan Alexis Glaunès, Linda Marrakchi-Kacem, Johanne Germain, Claire Boutet, Claire Cury, Lucie Hertz-Pannier, Alexandre Vignaud, Stanley Durrleman, Thomas R. Henry, Pierre-François van de Moortele, Alain Trouvé, and Olivier Colliot
Published: 2021
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20. Calibrationless Oscar-Based Image Reconstruction in Compressed Sensing Parallel MRI.

Author: Loubna El Gueddari, Philippe Ciuciu, Emilie Chouzenoux, Alexandre Vignaud, and Jean-Christophe Pesquet
Published: 2019
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21. Analysis vs Synthesis-based Regularization for Combined Compressed Sensing and Parallel MRI Reconstruction at 7 Tesla.

Author: Hamza Cherkaoui, Loubna El Gueddari, Carole Lazarus, Antoine Grigis, Fabrice Poupon, Alexandre Vignaud, Samuel Farrens, Jean-Luc Starck, and Philippe Ciuciu
Published: 2018
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22. Self-Calibrating Nonlinear Reconstruction Algorithms for Variable Density Sampling and Parallel Reception MRI.

Author: Loubna El Gueddari, Carole Lazarus, H. Carrie, Alexandre Vignaud, and Philippe Ciuciu
Published: 2018
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23. Optimizing full 3D SPARKLING trajectories for high-resolution T2*-weighted Magnetic Resonance Imaging.

Author: Chaithya G. R., Pierre Weiss, Guillaume Daval-Frerot, Aurélien Massire, Alexandre Vignaud, and Philippe Ciuciu
Published: 2021

24. Is good old GRAPPA dead?

Author: Zaccharie Ramzi, Alexandre Vignaud, Jean-Luc Starck, and Philippe Ciuciu
Published: 2021

25. Efficient optimization of chemical exchange saturation transfer MRI at 7 T using universal pulses and virtual observation points

Author: Vincent Gras, Luisa Ciobanu, Nicolas Boulant, Franck Mauconduit, Thaddée Delebarre, and Alexandre Vignaud
Subjects: Radiology, Nuclear Medicine and imaging
Published: 2023

26. Intra-subject multi-slab registration: Application to hippocampal ultra-high resolution imaging at 7T.

Author: Linda Marrakchi-Kacem, Alexandre Vignaud, Julien Sein, Johanne Germain, Thomas R. Henry, Cyril Poupon, Lucie Hertz-Pannier, Stéphane Lehéricy, Olivier Colliot, Pierre-François van de Moortele, and Marie Chupin
Published: 2016
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27. Improving spreading projection algorithm for rapid k‐space sampling trajectories through minimized off‐resonance effects and gridding of low frequencies

Author: Chaithya Giliyar Radhakrishna, Guillaume Daval‐Frérot, Aurélien Massire, Alexandre Vignaud, and Philippe Ciuciu
Subjects: Radiology, Nuclear Medicine and imaging
Published: 2023

28. Common Workflow Language & European Open Science Cloud pour l'implémentation de l'imagerie Quantitative de Susceptibilité Magnétique (QSM) du cerveau

Author: Miguel Guevara, Davy Cam, Jacques Badagbon, Stéphane Roche, Michel Bottlaender, Yann Cointepas, Jean-François Mangin, Ludovic de Rochefort, and Alexandre Vignaud
Subjects: QSM, aging, iron load
Abstract: Implémentation d'un pipeline pour le traitement des images IRM 7T pour l’imagerie QSM, défini avec Common Workflow Language (CWL) qui garantit sa pérennité et sa portabilité. En outre, on montre la faisabilité de ce type de traitement réalisé dans l’environnement Cloud des infrastructures Européennes de recherche.&nbsp
Published: 2023
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29. Physiological variability of the tympanic membrane temperature as an RF safety metric assessment

Author: Caroline Le Ster, Mikhail Kozlov, Alexandre Vignaud, and Nicolas Boulant
Abstract: RF exposure during MR exams induces heating of the exposed tissues. Measurement of tympanic membrane temperature with an infrared sensor has been used to estimate noninvasively the global RF-induced temperature rise. In this study, the tympanic membrane temperature was measured before and after having the volunteers lying for 15 minutes with earplugs with neither an RF nor a static magnetic field. Large physiological variations of temperature rise were observed across the volunteers after this dummy “exposure”, showing the low reliability of this metric to measure small temperature rises, that make it problematic for RF-induced temperature rise estimation.
Published: 2023
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30. Imagerie à ultra-haut champ

Author: Virginie CALLOT and Alexandre VIGNAUD
Abstract: Les systèmes d’imagerie par résonance magnétique à Ultra-Haut Champ, 7T notamment, ont ouvert de nouvelles perspectives pour explorer le corps humain. Ce chapitre vise à donner quelques clés pour mieux comprendre les avantages, inconvénients et challenges, physiques et méthodologiques, liés à ce type d’imagerie. Quelques exemples d’applications sont illustrés et les perspectives d’évolutions sont finalement brièvement discutées.
Published: 2023

31. Measuring radiofrequency field‐induced temperature variations in brain MRI exams with motion compensated MR thermometry and field monitoring

Author: Franck Mauconduit, Nicolas Boulant, Christian Mirkes, Caroline Le Ster, and Alexandre Vignaud
Subjects: Ground truth, Motion compensation, Materials science, Field (physics), Phantoms, Imaging, Temperature, Brain, Specific absorption rate, Thermometry, Magnetic Resonance Imaging, Compensation (engineering), Root mean square, Electromagnetic coil, Humans, Radiology, Nuclear Medicine and imaging, Lead (electronics), Biomedical engineering
Abstract: PURPOSE An MR thermometry (MRT) method with motion and field fluctuation compensation is proposed to measure non-invasively sub-degree brain temperature variations occurring through radiofrequency (RF) power deposition during MR exams. METHODS MRT at 7T with a multi-slice echo planar imaging (EPI) sequence and concurrent field monitoring was first tested in vitro to assess accuracy in the presence of external field perturbations, an optical probe being used for ground truth. In vivo, this strategy was complemented by a motion compensation scheme based on a dictionary pre-scan, as reported in some previous work, and was adapted to the human brain. Precision reached with this scheme was assessed on eight volunteers with a 5 minute-long low specific absorption rate (SAR) scan. Finally, temperature rise in the brain was measured twice on the same volunteers and with the same strategy, this time by employing a 20-minutes scan at the maximum SAR delivered with a commercial volume head coil. RESULTS In vitro, the root mean square (RMS) error between optical probe and MRT measurements was 0.02°C with field sensor correction. In vivo, the low SAR scan returned a precision in temperature change measurement with field monitoring and motion compensation of 0.05°C. The 20-minutes maximum SAR scan returned a temperature rise throughout the inner-brain in the range of 0-0.2°C. Brain periphery remained too sensitive with respect to motion to lead to equally conclusive results. CONCLUSION Sub-degree temperature rise in the inner human brain was characterized experimentally throughout RF exposure. Potential applications include improvement of human thermal models and revision of safety margins.
Published: 2021

32. Magnetic field strength dependent SNR gain at the center of a spherical phantom and up to 11.7T

Author: Caroline Le Ster, Andrea Grant, Pierre‐François Van de Moortele, Alejandro Monreal‐Madrigal, Gregor Adriany, Alexandre Vignaud, Franck Mauconduit, Cécile Rabrait‐Lerman, Benedikt A. Poser, Kâmil Uğurbil, Nicolas Boulant, MRI, and RS: FPN CN 5
Subjects: Phantoms, Imaging, Radio Waves, POWER, Magnetic Resonance Imaging, Magnetic Fields, field strength, TO-NOISE-RATIO, PATTERNS, Humans, ARRAY, Radiology, Nuclear Medicine and imaging, signal-to-noise ratio, SENSITIVITY, MRI, volume coil
Abstract: PURPOSE: The SNR at the center of a spherical phantom of known electrical properties was measured in quasi-identical experimental conditions as a function of magnetic field strength between 3 T and 11.7 T.METHODS: The SNR was measured at the center of a spherical water saline phantom with a gradient recalled echo sequence. Measurements were performed at NeuroSpin at 3, 7, and 11.7 T. The phantom was then shipped to Maastricht University and then to the University of Minnesota for additional data points at 7, 9.4, and 10.5 T. Experiments were carried out with the exact same type of birdcage volume coil (except at 3 T, where a similar coil was used) to attempt at isolating the evolution of SNR with field strength alone. Phantom electrical properties were characterized over the corresponding frequency range.RESULTS: Electrical properties were found to barely vary over the frequency range. Removing the influence of the flip-angle excitation inhomogeneity was crucial, as expected. After such correction, measurements revealed a gain of SNR growing as B0 1.94 ± 0.16 compared with B0 2.13 according to ultimate intrinsic SNR theory.CONCLUSIONS: By using quasi-identical experimental setups (RF volume coil, phantom, electrical properties, and protocol), this work reports experimental data between 3 T and 11.7 T, enabling the comparison with SNR theories in which conductivity and permittivity can be assumed to be constant with respect to field strength. According to ultimate SNR theory, these results can be reasonably extrapolated to the performance of receive arrays with greater than about 32 elements for central SNR in the same spherical phantom.
Published: 2022

33. Irm cerebrale du sodium rapide avec sparkling 3d sous-echantillonnee à 7 tesla

Author: Renata Porciuncula Baptista, Mathieu Naudin, Chaithya G R, Guillaume Daval-Frerot, Franck Mauconduit, Alexa Haeger, Sandro Romanzetti, Marc Lapert, Philippe Ciuciu, Cecile Rabrait-Lerman, Remy Guillevin, Alexandre Vignaud, and Fawzi Boumezbeur
Subjects: Radiological and Ultrasound Technology, Radiology, Nuclear Medicine and imaging, Neurology (clinical)
Published: 2023

34. Support vector driven Markov random fields towards DTI segmentation of the human skeletal muscle.

Author: Radhouène Neji, Gilles Fleury, Jean-François Deux, Alain Rahmouni, Guillaume Bassez, Alexandre Vignaud, and Nikos Paragios
Published: 2008
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35. Iterative static field map estimation for off-resonance correction in non-Cartesian susceptibility weighted imaging

Author: Guillaume Daval‐Frérot, Aurélien Massire, Boris Mailhe, Mariappan Nadar, Alexandre Vignaud, and Philippe Ciuciu
Subjects: Echo-Planar Imaging, Phantoms, Imaging, Image Processing, Computer-Assisted, Brain, Humans, Radiology, Nuclear Medicine and imaging, Artifacts, Magnetic Resonance Imaging, Algorithms
Abstract: Patient-induced inhomogeneities in the magnetic field cause distortions and blurring during acquisitions with long readouts such as in susceptibility-weighted imaging (SWI). Most correction methods require collecting an additionalThe staticThe main step is to combine and unfold the multi-channel phase maps wrapped many times, and several competing algorithms are compared for this purpose. Four in vivo brain data sets collected using the recently proposed 3D spreading projection algorithm for rapid k-space sampling (SPARKLING) readouts are used to assess the proposed method.The estimated 3D field maps generated with a 0.6 mm isotropic spatial resolution provide overall similar off-resonance corrections compared to reference corrections based on an externalA static
Published: 2022

36. La deregulation energetique evaluee par rmn multi-noyaux 23na/31p a 7 tesla au cours de la sclerose en plaques

Author: Juliette Dufour, Mariem Hamzaoui, Renata Porciuncula Baptista, Giacomo Boffa, Vito AG Ricigliano, Francesca Branzoli, Alexandre Vignaud, Matilde Inglese, Bruno Stankoff, Fawzi Boumezbeur, and Benedetta Bodini
Subjects: Radiological and Ultrasound Technology, Radiology, Nuclear Medicine and imaging, Neurology (clinical)
Published: 2023

37. Robust imaging of hippocampal inner structure at 7T: in vivo acquisition protocol and methodological choices.

Author: Linda Marrakchi-Kacem, Alexandre Vignaud, Julien Sein, Johanne Germain, Thomas R. Henry, Cyril Poupon, Lucie Hertz-Pannier, Stéphane Lehéricy, Olivier Colliot, Pierre-François van de Moortele, and Marie Chupin
Published: 2016

38. New 'restricted SAR mode' definition based on a thermal conservative model for relaxed unconditional safe in vivo experiments

Author: Natalia Dudysheva, Nicolas Boulant, and Alexandre Vignaud
Subjects: body regions, fungi, skin and connective tissue diseases
Abstract: In this work, we propose to extend the capacities of ultra-low SAR protocol used in coil design. A developed restricted SAR protocol holds the worst-case SAR below the threshold by constraining the total transmitted RF power. Since SAR reflects tissue heating, we exploit a conservative thermal model to derive relaxed SAR constraints depending on acquisition time. This enables to extend the options available for sequences played under this mode, including fat suppression, higher image resolution, or decreased TR.
Published: 2022
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39. MetaPulse2D: methodology to enable universal slice specic spokes pulses in parallel transmission

Author: Franck Mauconduit, Vincent Gras, Alexandre Vignaud, and Nicolas Boulant
Abstract: When using a slice-by-slice RF shimming or multi-spokes pulses in 2D parallel transmission MRI, the solution is valid for a specic slice position and orientation. Here, we introduce a new pulse concept were the spoke coecients and gradient blips are smooth functions of the slice position and orientation. We show that this design performs better than CP mode and equivalent to other designs. However, it enables to tilt or reposition slices without requiring additional optimization. This solution promotes signal smoothness through slices. Additionally, it can be pre-computed using the Universal Pulse concept or computed online using a tailored approach.
Published: 2022
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40. Measuring RF field-induced temperature variations in brain MRI exams with motion compensated MRT and field monitoring

Author: Caroline Le Ster, Franck Mauconduit, Christian Mirkes, Alexandre Vignaud, and Nicolas Boulant
Abstract: Sub-degree brain temperature rise occurring through RF power deposition during the MR exam was measured with MR thermometry at 7T using a multi-slice EPI sequence and concurrent field monitoring. This sequence was first tested in vitro with field perturbations, an optical probe being used for ground truth measurements, and the accuracy of the method reached 0.02°C. In vivo, this methodology was complemented by a motion compensation step and precision reached 0.05°C. After 20-min of scanning at maximal SAR, temperature rise induced by RF power deposition throughout the inner brain reached 0-0.2°C, well below the values predicted by thermal models.
Published: 2022
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41. Pitfalls of data-driven tSNR optimized coil combination for fMRI

Author: Redouane Jamil, Franck Mauconduit, Caroline Le Ster, Philipp Ehses, Benedikt A Poser, Alexandre Vignaud, and Nicolas Boulant
Abstract: Summary of Main Findings: Analytical expressions for optimal tSNR and t-score for the mean coil combinations are described and compared to the commonly used covSoS coil combination. Findings suggest that optimal tSNR or t-score for the mean do not guarantee better BOLD signal detection in fMRI time series. Synopsis: For MRI with a multi-receiver RF coil, one image per coil element and per time frame is obtained. The final image is typically calculated from the root sum of squares (rSoS) combination across channels. While this combination approach is quasi-optimal for SNR, it is not necessarily optimal for temporal SNR (tSNR) of the time-series. We present two analytical and voxel-wise coil combination expressions reaching optimality in tSNR and t-score for the mean (TSM) respectively. Their BOLD sensitivity is compared to the gold standard covariance root sum of squares. Both improved tSNR and TSM but yielded weaker t-scores than covSoS.
Published: 2022
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42. Hilbert fractal inspired dipoles for passive RF shimming in ultra-high field MRI

Author: Tania Vergara Gomez, Marc Dubois, Kaizad Rustomji, Elodie Georget, Tryfon Antonakakis, Alexandre Vignaud, Stanislas Rapacchi, Olivier Girard, F. Kober, Stefan Enoch, et al.
Published: 2022
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43. Simultaneous proton density, T 1 , T 2 , and flip‐angle mapping of the brain at 7 T using multiparametric 3D SSFP imaging and parallel‐transmission universal pulses

Author: Denis Le Bihan, Lisa Leroi, L. Hertz-Pannier, Vincent Gras, Ludovic de Rochefort, Romain Valabregue, Franck Mauconduit, Alexandre Vignaud, Mathilde Ripart, Emilie Poirion, Nicolas Boulant, Mathieu Santin, Service NEUROSPIN (NEUROSPIN), Université Paris-Saclay-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Institut du Cerveau = Paris Brain Institute (ICM), Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Institut National de la Santé et de la Recherche Médicale (INSERM)-CHU Pitié-Salpêtrière [AP-HP], Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Sorbonne Université (SU)-Sorbonne Université (SU)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Centre de résonance magnétique biologique et médicale (CRMBM), Aix Marseille Université (AMU)-Assistance Publique - Hôpitaux de Marseille (APHM)-Centre National de la Recherche Scientifique (CNRS), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Institut du Cerveau et de la Moëlle Epinière = Brain and Spine Institute (ICM), Institut National de la Santé et de la Recherche Médicale (INSERM)-CHU Pitié-Salpêtrière [AP-HP], Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Sorbonne Université (SU)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Sorbonne Université (SU)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), and Assistance Publique - Hôpitaux de Marseille (APHM)-Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS)
Subjects: [SDV.IB.IMA]Life Sciences [q-bio]/Bioengineering/Imaging, [SDV]Life Sciences [q-bio], relaxometry, Universal Pulses, Parallel transmission, quantitative MRI, 030218 nuclear medicine & medical imaging, [SPI]Engineering Sciences [physics], 03 medical and health sciences, 0302 clinical medicine, Flip angle, Universal Pulses 2, Robustness (computer science), Effective diffusion coefficient, Radiology, Nuclear Medicine and imaging, Image resolution, [PHYS]Physics [physics], Physics, T2, T1, Specific absorption rate, Pulse sequence, Steady-state free precession imaging, Computational physics, Parallel communication, 030217 neurology & neurosurgery
Abstract: International audience; Purpose: Performing simultaneous quantitative MRI at ultra-high field is challenging, as B0 and B1 + heterogeneities as well as Specific Absorption Rate increase. Too large deviations of flip angle from the target can induce biases and impair signal-to-noise ratio in the quantification process. In this work, we use calibration-free parallel transmission, a dedicated pulse sequence parameter optimization and signal fitting to recover 3D proton density, flip angle, T1 and T2 maps over the whole brain, in a clinically suitable time. Methods: Eleven optimized contrasts were acquired with an unbalanced Steady-State Free Precession sequence by varying flip angle amplitude and radiofrequency phase cycling increment, at a 1.0x1.0x3.0mm 3 resolution. Acquisition time was of 16min36sec for the whole brain. Parallel transmission and Universal Pulses were used to mitigate B1 + heterogeneity to improve the results' reliability over six healthy volunteers (3 females/males, age 22.6±2.7 years-old). Quantification of the physical parameters was performed by fitting acquired contrasts to the simulated ones using the Bloch-Torrey equations with a realistic diffusion coefficient. Results: Whole-brain 3D maps of effective flip angle, PD and relaxation times were estimated. Parallel transmission improved the robustness of the results at 7T. Results were in accordance with literature and with measurements from standard methods. Conclusion: These preliminary results show robust PD, FA, T1 and T2 map retrieval. Other parameters, such as Apparent Diffusion Coefficient, could be assessed. With further optimization in the acquisition, scan time could be reduced and spatial resolution increased to bring this multi-parametric quantification method to clinical research routine at 7-tesla.
Published: 2020

44. Imaging the aging brain: study design and baseline findings of the SENIOR cohort

Author: Lucie Hertz-Pannier, Marie Sarazin, Alexa Haeger, Michel Bottlaender, Jean-François Mangin, Jean-Robert Deverre, Alexandre Vignaud, Antoine Grigis, Cyril Poupon, Vincent Frouin, and Fawzi Boumezbeur
Subjects: Male, Oncology, medicine.medical_specialty, Aging, Cognitive Neuroscience, Cognitive decline, Neuropsychological Tests, Intra-person across-test variability, Neurodegenerative disease, lcsh:RC346-429, Imaging, lcsh:RC321-571, Cohort Studies, White matter, Alzheimer Disease, Internal medicine, medicine, Humans, Dementia, Aging brain, Longitudinal Studies, lcsh:Neurosciences. Biological psychiatry. Neuropsychiatry, lcsh:Neurology. Diseases of the nervous system, Aged, medicine.diagnostic_test, business.industry, Research, Prevention, Brain, Neuropsychological test, Biomarker, Middle Aged, medicine.disease, Magnetic Resonance Imaging, Hyperintensity, medicine.anatomical_structure, Neurology, Positron-Emission Tomography, Brain size, Cohort, Female, Neurology (clinical), business, Alzheimer’s disease
Abstract: Background Current demographic trends point towards an aging society entailing increasing occurrence and burden of neurodegenerative diseases. In this context, understanding physiological aging and its turning point into neurodegeneration is essential for the development of possible biomarkers and future therapeutics of brain disease. Methods The SENIOR study represents a longitudinal, observational study including cognitively healthy elderlies aged between 50 and 70 years old at the time of inclusion, being followed annually over 10 years. Our multimodal protocol includes structural, diffusion, functional, and sodium magnetic resonance imaging (MRI) at 3 T and 7 T, positron emission tomography (PET), blood samples, genetics, audiometry, and neuropsychological and neurological examinations as well as assessment of neuronal risk factors. Results One hundred forty-two participants (50% females) were enrolled in the SENIOR cohort with a mean age of 60 (SD 6.3) years at baseline. Baseline results with multiple regression analyses reveal that cerebral white matter lesions can be predicted by cardiovascular and cognitive risk factors and age. Cardiovascular risk factors were strongly associated with juxtacortical and periventricular lesions. Intra-subject across-test variability as a measure of neuropsychological test performance and possible cognitive marker predicts white matter volume and is significantly associated with risk profile. Division of the cohort into subjects with a higher and lower risk profile shows significant differences in intra-subject across-test variability and volumes as well as cortical thickness of brain regions of the temporal lobe. There is no difference between the lower- and higher-risk groups in amyloid load using PET data from a subset of 81 subjects. Conclusions We here describe the study protocol and baseline findings of the SENIOR observational study which aim is the establishment of integrated, multiparametric maps of normal aging and the identification of early biomarkers for neurodegeneration. We show that intra-subject across-test variability as a marker of neuropsychological test performance as well as age, gender, and combined risk factors influence neuronal decline as represented by decrease in brain volume, cortical thickness, and increase in white matter lesions. Baseline findings will be used as underlying basis for the further implications of aging and neuronal degeneration as well as examination of brain aging under different aspects of brain pathology versus physiological aging.
Published: 2020

45. Open birdcage coil for head imaging at 7T

Author: Nikolai I. Avdievich, A. Nikulin, Abdelwaheb Ourir, Alexandre Vignaud, D. Berrahou, Julien de Rosny, Institut Langevin - Ondes et Images (UMR7587) (IL), Ecole Superieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Service NEUROSPIN (NEUROSPIN), Université Paris-Saclay-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), High-Field MR Center, Max Planck Institute for Biological Cybernetics, and Multiwave Imaging
Subjects: ultra-high-field MRI, Acoustics, brain imaging, Tracking (particle physics), Imaging phantom, 030218 nuclear medicine & medical imaging, head coil, 03 medical and health sciences, 0302 clinical medicine, Humans, Radiology, Nuclear Medicine and imaging, [PHYS.COND.CM-MSQHE]Physics [physics]/Condensed Matter [cond-mat]/Mesoscopic Systems and Quantum Hall Effect [cond-mat.mes-hall], Physics, open coil, Phantoms, Imaging, Homogeneity (statistics), Brain, Specific absorption rate, Equipment Design, Magnetic Resonance Imaging, Transfer matrix, Symmetry (physics), Magnetic field, birdcage coil, Electromagnetic coil, Head, 030217 neurology & neurosurgery
Abstract: Purpose: To theoretically describe, design, and test the new geometry of the birdcage coil for 7 Tesla anatomical brain imaging, which includes a large window on top, without deliberately jeopardizing its homogeneity and efficiency. This opencage will not only improve patient comfort but also enable the volunteer to follow functional MRI stimuli. This design could also facilitate the tracking of patient compliance and enable better correction of the movement. Methods: Via the transfer matrix approach, a birdcage-like coil with a nonperiodic distribution of rungs is constructed with optimized currents in the coil rungs. Subsequently, the coil is adjusted in full-wave simulations. Then, the coil is assembled, fine-tuned, and matched on the bench. Finally, these results are confirmed experimentally on a phantom and in vivo. Results: Indeed, the computed isolation of -14.9 dB between the feeding ports of the coil and the symmetry of the circular polarized mode pattern transmit RF magnetic field ( B+1 ) showed that the coil was properly optimized. An experimental assessment of the developed coil showed competitive transmit efficiency and coverage compared with the conventional birdcage coil of similar size. Conclusion: The proposed opencage coil can be designed and work without a dramatic drop of performance in terms of the B+1 field homogeneity, transmit efficiency ( (B+1) / √Pref ), peak local specific absorption rate ( SAR10g ) and SAR efficiency ( (B+1) / √SAR10g ).
Published: 2021

46. CRPE - L'épreuve écrite d'histoire, géographie, EMC

Author: null Alexandre Vignaud and null Géraldine Camy
Published: 2021

47. Tissue sodium concentration and sodium T1 mapping of the human brain at 3 T using a Variable Flip Angle method

Author: Arthur Coste, Fawzi Boumezbeur, Sandro Romanzetti, Denis Le Bihan, Cécile Rabrait-Lerman, Alexandre Vignaud, Kathrin Reetz, and Guillaume Madelin
Subjects: Materials science, Sodium, Biomedical Engineering, Biophysics, Healthy subjects, Specific absorption rate, chemistry.chemical_element, Human brain, 030218 nuclear medicine & medical imaging, 03 medical and health sciences, 0302 clinical medicine, medicine.anatomical_structure, chemistry, Repetition Time, Flip angle, medicine, Sodium MRI, Radiology, Nuclear Medicine and imaging, Ultrashort echo time, 030217 neurology & neurosurgery, Biomedical engineering
Abstract: Purpose The state-of-the-art method to quantify sodium concentrations in vivo consists in a fully relaxed 3D spin-density (SD) weighted acquisition. Nevertheless, most sodium MRI clinical studies use short-TR SD acquisitions to reduce acquisition durations. We present a clinically viable implementation of the Variable Flip Angle (VFA) method for robust and clinically viable quantification of total sodium concentration (TSC) and longitudinal relaxation rates in vivo in human brain at 3 T. Methods Two non-Cartesian steady-state spoiled ultrashort echo time (UTE) scans, performed at optimized flip angles, repetition time and pulse length determined under specific absorption rate constraints, are used to simultaneously compute T1 and total sodium concentration (TSC) maps using the VFA method. Images are reconstructed using the non-uniform Fast Fourier Transform algorithm and TSC maps are corrected for possible inhomogeneity of coil transmission and reception profiles. Fractioned acquisitions are used to correct for potential patient motion. TSC quantifications obtained using the VFA method are validated at first in comparison with a fully-relaxed SD acquisition in a calibration phantom. The robustness of similar VFA acquisitions are compared to the short-TR SD approach in vivo on seven healthy volunteers. Results The VFA method resulted in consistent TSC and T1 estimates across our cohort of healthy subjects, with mean TSC of 38.1 ± 5.0 mmol/L and T1 of 39.2 ± 4.4 ms. These results are in agreement with previously reported values in literature TSC estimations and with the predictions of a 2-compartment model. However, the short-TR SD acquisition systematically underestimated the sodium concentration with a mean TSC of 31 ± 4.5 mmol/L. Conclusion The VFA method can be applied successfully to image sodium at 3 T in about 20 min and provides robust and intrinsically T1-corrected TSC maps.
Published: 2019

48. An empirical study of the maximum degree of undersampling in compressed sensing for T2*-weighted MRI

Author: Philippe Ciuciu, Pierre Weiss, Carole Lazarus, and Alexandre Vignaud
Subjects: Computer science, Image quality, Biomedical Engineering, Biophysics, Context (language use), 02 engineering and technology, Imaging phantom, 030218 nuclear medicine & medical imaging, 03 medical and health sciences, Acceleration, 0302 clinical medicine, Compressed sensing, Undersampling, 0202 electrical engineering, electronic engineering, information engineering, 020201 artificial intelligence & image processing, Radiology, Nuclear Medicine and imaging, Focus (optics), Image resolution, Algorithm
Abstract: Magnetic Resonance Imaging (MRI) is one of the most dynamic and safe imaging modalities used in clinical routine today. Yet, one major limitation to this technique resides in its long acquisition times. Over the last decade, Compressed Sensing (CS) has been increasingly used to address this issue and offers to shorten MR scans by reconstructing images from undersampled Fourier data. Nevertheless, a quantitative guide on the degree of acceleration applicable to a given acquisition scenario is still lacking today, leading in practice to a trial-and-error approach in the selection of the appropriate undersampling factor. In this study, we shortly point out the existing theoretical sampling results in CS and their limitations which motivate the focus of this work: an empirical and quantitative analysis of the maximum degree of undersampling allowed by CS in the specific context of T 2 * -weighted MRI. We make use of a generic method based on retrospective undersampling to quantitatively deduce the maximum acceleration factor R max which preserves a desired image quality as a function of the image resolution and the available signal-to-noise ratio (SNR). Our results quantify how larger acceleration factors can be applied to higher resolution images as long as a minimum SNR is guaranteed. In practice however, the maximum acceleration factor for a given resolution appears to be constrained by the available SNR inherent to the considered acquisition. Our analysis enables to take this a priori knowledge into account, allowing to derive a sequence-specific maximum acceleration factor adapted to the intrinsic SNR of any MR pipeline. These results obtained on an analytical T 2 * -weighted phantom image were corroborated by prospective experiments performed on MR data collected with radial trajectories on a 7 T scanner with the same contrast. The proposed framework allows to study other sequence weightings and therefore better optimize sequences when accelerated using CS.
Published: 2018

49. 7T Epilepsy Task Force Consensus Recommendations on the Use of 7T MRI in Clinical Practice

Author: Jacobus F.A. Jansen, Thomas R. Henry, Pierre-Francois Van de Moortele, Boris C. Bernhardt, Natalie L. Voets, Jonathan R. Polimeni, Tim J. Veersema, Lucie Hertz-Pannier, Jullie W. Pan, Giske Opheim, Lars H. Pinborg, Neda Bernasconi, Michael T. Jurkiewicz, Jean-Philippe Ranjeva, Mirco Cosottini, Heath R. Pardoe, Srinivasan Mukundan, Karl Rössler, Irene Wang, Renzo Guerrini, Albert J. Colon, Karin Markenroth Bloch, Maria Vargas, Andrea Bernasconi, Isabella M. Björkman-Burtscher, Esther Steijvers, Sandhitsu R. Das, Serge Vulliemoz, Rong Xue, Alexandre Vignaud, Shuli Liang, Ruoyun Emily Ma, Siegfried Trattnig, Maxime Guye, Stephen E. Jones, Fabrice Bartolomei, Kathryn A. Davis, Steven M. Stufflebeam, Sara Inati, Joel M. Stein, Christopher Wiggins, Anja G. van der Kolk, Maria Strandberg, Ali R. Khan, Neurobiology Research Unit, Department of Neurology Rigshospitalet Copenhagen University Hospital, UCPH, Faculty of Health and Medical Sciences, UCPH, Utrecht Brain Center [UMC], University Medical Center [Utrecht], Department of Radiology University Medical Center Utrecht, Lund University [Lund], Department of Neurology Neurophysiology and Neurosurgery, ACE Kempenhaeghe/MUMC, Heeze/Maastricht, PENN Epilepsy Center, University of Pennsylvania, Department of Neurology University of Minnesota, Minneapolis, Department of Radiology and Nuclear Medicine Maastricht University Medical Center, School for Mental Health and Neuroscience [Maastricht] (MHeNs), Maastricht University [Maastricht], Imaging Institute [Cleveland], Cleveland Clinic, Department of Neurology and Radiology University of Pittsburg, Medizinische Universität Wien = Medical University of Vienna, Department of Radiology Hospital of the University of Pennsylvania, Philadelphia, Departments of Neurology and Clinical Sciences Lund University Hospital, Center for Magnetic Resonance Research [Minneapolis] (CMRR), University of Minnesota Medical School, University of Minnesota System-University of Minnesota System, Neuroradiology Division, Diagnostic Unit University Hospitals and Faculty of Medicine of Geneva, Epilepsy Center Cleveland Clinic, Institut de Neurosciences des Systèmes (INS), Aix Marseille Université (AMU)-Institut National de la Santé et de la Recherche Médicale (INSERM), Service de neurophysiologie clinique [Hôpital de la Timone - APHM], Hôpital de la Timone [CHU - APHM] (TIMONE), McConnell Brain Imaging Centre (MNI), Montreal Neurological Institute and Hospital, McGill University = Université McGill [Montréal, Canada]-McGill University = Université McGill [Montréal, Canada], University of Gothenburg (GU), Department of Translational Research on New Technologies in Medicine and Surgery, University of Pisa - Università di Pisa, Department of Neurology University of Pennsylvania, Philadelphia, Building large instruments for neuroimaging: from population imaging to ultra-high magnetic fields (BAOBAB), Service NEUROSPIN (NEUROSPIN), Université Paris-Saclay-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), EEG Section, NINDS, NIH, Bethesda, Department of Medical Imaging Children's Hospital at London Health Sciences Centre, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Imaging Research Laboratories, Robarts Research Institute, London, Functional Neurosurgery Department Beijing Children's Hospital of Capital Medical University, Beijing, Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Epilepsy Clinic, Department of Neurology, Rigshospitalet Copenhagen University Hospital, Harvard-MIT Division of Health Sciences and Technology [Cambridge], Massachusetts Institute of Technology (MIT), Athinoula A. Martinos Center for Biomedical Imaging, Harvard Medical School [Boston] (HMS)-Massachusetts General Hospital [Boston], Centre de résonance magnétique biologique et médicale (CRMBM), Aix Marseille Université (AMU)-Assistance Publique - Hôpitaux de Marseille (APHM)-Centre National de la Recherche Scientifique (CNRS), Centre d'Exploration Métabolique par Résonance Magnétique [Hôpital de la Timone - APHM] (CEMEREM), Hôpital de la Timone [CHU - APHM] (TIMONE)-Centre de résonance magnétique biologique et médicale (CRMBM), Aix Marseille Université (AMU)-Assistance Publique - Hôpitaux de Marseille (APHM)-Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)-Assistance Publique - Hôpitaux de Marseille (APHM)-Centre National de la Recherche Scientifique (CNRS), Scannexus Ultrahigh Field MRI Research Center, Maastricht, Department of Radiology and Nuclear Medicine Meander Medical Center, Amersfoort, Laboratoire d'Imagerie et de Spectroscopie (LRMN), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Wellcome Trust Centre for Integrative Neuroimaging (WIN - FMRIB), University of Oxford, Université de Genève = University of Geneva (UNIGE), State Key Laboratory of Cognitive Neuroscience and Learning, International Data Group/McGovern Institute for Brain Research, Beijing Normal University, Beijing 100875, China, Università degli Studi di Firenze = University of Florence (UniFI), IMAGO 7 Foundation, Florence, UMC Utrecht Brain Center, Utrecht University, Lund University Bioimaging Center, Lund University, University of Pennsylvania [Philadelphia], School for Mental Health and Neuroscience, Maastricht University, Department of Neurosurgery Medical University of Vienna, Department of Biomedical Imaging and Image-guided Therapy [Medical University of Vienna], High Field MR Center, Medical University of Vienna, Institut National de la Santé et de la Recherche Médicale (INSERM)-Aix Marseille Université (AMU), Department of Radiology Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Unité Baobab (BAOBAB), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Massachusetts General Hospital [Boston]-Harvard Medical School [Boston] (HMS), Assistance Publique - Hôpitaux de Marseille (APHM)-Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS), Centre d'Exploration Métabolique par Résonance Magnétique [Hôpital de la Timone - AP-HM] (CEMEREM), Assistance Publique - Hôpitaux de Marseille (APHM)-Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS)-Assistance Publique - Hôpitaux de Marseille (APHM)-Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS)- Hôpital de la Timone [CHU - APHM] (TIMONE), University of Oxford [Oxford], EEG and Epilepsy Unit Neurology, Department of Clinical Neurosciences, University Hospitals and Faculty of Medicine of Geneva, and Neuroscience Department Children's Hospital A. Meyer-University of Florence
Subjects: medicine.medical_specialty, Neurology, Consensus, Referral, [SDV.IB.IMA]Life Sciences [q-bio]/Bioengineering/Imaging, IMAGES, MEDLINE, ddc:616.0757, PROSPECTIVE MOTION-CORRECTION, CLASSIFICATION, 3T, 03 medical and health sciences, Epilepsy, 0302 clinical medicine, Medicine, Humans, In patient, Medical physics, 030212 general & internal medicine, Views & Reviews, medicine.diagnostic_test, business.industry, Task force, Brain, Magnetic resonance imaging, medicine.disease, CEREBRAL CAVERNOUS MALFORMATIONS, Magnetic Resonance Imaging, 3. Good health, ddc:616.8, Clinical Practice, FMRI, Neurology (clinical), business, 030217 neurology & neurosurgery, SYSTEM
Abstract: International audience; Identifying a structural brain lesion on MRI has important implications in epilepsy and is the most important factor that correlates with seizure freedom after surgery in patients with drug-resistant focal onset epilepsy. However, at conventional magnetic field strengths (1.5 and 3T), only approximately 60%–85% of MRI examinations reveal such lesions. Over the last decade, studies have demonstrated the added value of 7T MRI in patients with and without known epileptogenic lesions from 1.5 and/or 3T. However, translation of 7T MRI to clinical practice is still challenging, particularly in centers new to 7T, and there is a need for practical recommendations on targeted use of 7T MRI in the clinical management of patients with epilepsy. The 7T Epilepsy Task Force—an international group representing 21 7T MRI centers with experience from scanning over 2,000 patients with epilepsy—would hereby like to share its experience with the neurology community regarding the appropriate clinical indications, patient selection and preparation, acquisition protocols and setup, technical challenges, and radiologic guidelines for 7T MRI in patients with epilepsy. This article mainly addresses structural imaging; in addition, it presents multiple nonstructural MRI techniques that benefit from 7T and hold promise as future directions in epilepsy. Answering to the increased availability of 7T MRI as an approved tool for diagnostic purposes, this article aims to provide guidance on clinical 7T MRI epilepsy management by giving recommendations on referral, suitable 7T MRI protocols, and image interpretation.
Published: 2021

50. A Diffeomorphic Vector Field Approach to Analyze the Thickness of the Hippocampus from 7T MRI

Author: Alexandre Vignaud, Lucie Hertz-Pannier, Alexis Guyot, Claire Cury, Ana B. Graciano Fouquier, Emilie Gerardin, Claire Boutet, Alain Trouvé, Stanley Durrleman, Joan Alexis Glaunès, Johanne Germain, Marie Chupin, Olivier Colliot, Linda Marrakchi-Kacem, Thomas R. Henry, Pierre-Francois Van de Moortele, Institut du Cerveau = Paris Brain Institute (ICM), Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Institut National de la Santé et de la Recherche Médicale (INSERM)-CHU Pitié-Salpêtrière [AP-HP], Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Sorbonne Université (SU)-Sorbonne Université (SU)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Algorithms, models and methods for images and signals of the human brain (ARAMIS), Sorbonne Université (SU)-Inria de Paris, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Institut du Cerveau = Paris Brain Institute (ICM), Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Sorbonne Université (SU)-Sorbonne Université (SU)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Institut National de la Santé et de la Recherche Médicale (INSERM)-CHU Pitié-Salpêtrière [AP-HP], Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Sorbonne Université (SU)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), CATI Multicenter Neuroimaging Platform (CATI), Mathématiques Appliquées Paris 5 (MAP5 - UMR 8145), Institut National des Sciences Mathématiques et de leurs Interactions (INSMI)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Institut Supérieur de Biotechnologie de Sidi Thabet (ISBST), Université de la Manouba [Tunisie] (UMA), Neuroimagerie: méthodes et applications (Empenn), Institut National de la Santé et de la Recherche Médicale (INSERM)-Inria Rennes – Bretagne Atlantique, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-SIGNAUX ET IMAGES NUMÉRIQUES, ROBOTIQUE (IRISA-D5), Institut de Recherche en Informatique et Systèmes Aléatoires (IRISA), Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université de Bretagne Sud (UBS)-École normale supérieure - Rennes (ENS Rennes)-Institut National de Recherche en Informatique et en Automatique (Inria)-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS)-IMT Atlantique (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)-Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)-Institut de Recherche en Informatique et Systèmes Aléatoires (IRISA), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université de Bretagne Sud (UBS)-École normale supérieure - Rennes (ENS Rennes)-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS)-IMT Atlantique (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT), Service NEUROSPIN (NEUROSPIN), Université Paris-Saclay-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Institut National de la Santé et de la Recherche Médicale (INSERM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), University of Minnesota Medical School, University of Minnesota System, Center for Magnetic Resonance Research [Minneapolis] (CMRR), University of Minnesota System-University of Minnesota System, This work was supported by ANR (HM-TC, ANR-09-EMER-006), France Alzheimer (IRMA7), by the CATI project, by Investissements d’avenirANR-19-P3IA-0001 (PRAIRIE 3IA Institute) and ANR-10-IAIHU-06, by the Philippe foundation, and by the NSF/NIH/ANR program 'CollaborativeResearch in Computational Neuroscience' (HIPLAY7, NSF-CRCSN-1607835 and ANR-16-NEUC-0001-01)., ANR-09-EMER-0006,HM-TC,Modélisation des interactions entre l'hippocampe et le cortex dans ' la conscience temporelle', établie à partir de l'imagerie cérébrale multimodale anatomique et fonctionnelle(2009), ANR-19-P3IA-0001,PRAIRIE,PaRis Artificial Intelligence Research InstitutE(2019), ANR-10-IAHU-0006,IHU-A-ICM,Institut de Neurosciences Translationnelles de Paris(2010), ANR-16-NEUC-0001,HIPLAY7,Experimental and theoretical investigation of the multi-scale emergence of parametric working memory in prefrontal cortex recurrent networks(2016), Institut du Cerveau et de la Moëlle Epinière = Brain and Spine Institute (ICM), Institut National de la Santé et de la Recherche Médicale (INSERM)-CHU Pitié-Salpêtrière [APHP]-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Institut du Cerveau et de la Moëlle Epinière = Brain and Spine Institute (ICM), Institut National de la Santé et de la Recherche Médicale (INSERM)-CHU Pitié-Salpêtrière [APHP]-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Santé et de la Recherche Médicale (INSERM)-CHU Pitié-Salpêtrière [APHP]-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Université Paris Descartes - Paris 5 (UPD5)-Institut National des Sciences Mathématiques et de leurs Interactions (INSMI)-Centre National de la Recherche Scientifique (CNRS), Institut Supérieur de Biotechnologies [Sidi Thabet] (ISBST), Empenn, Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-Université de Bretagne Sud (UBS)-École normale supérieure - Rennes (ENS Rennes)-Institut National de Recherche en Informatique et en Automatique (Inria)-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)-Université de Rennes 1 (UR1), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-Université de Bretagne Sud (UBS)-École normale supérieure - Rennes (ENS Rennes)-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Centre de Mathématiques et de Leurs Applications (CMLA), École normale supérieure - Cachan (ENS Cachan)-Centre National de la Recherche Scientifique (CNRS), This work was supported by ANR (project HM-TC, grant number ANR-09-EMER-006), France Alzheimer Association (project IRMA7), by the CATI project (Fondation Plan Alzheimer), by the program Investissements d’avenir (grant number ANR-10-IAIHU-06), from the Philippe foundation, and by the joint NSF/NIH/ANR program 'Collaborative Research in Computational Neuroscience' (project HIPLAY7, grant number ANR-16-NEUC-0001-01)., ANR-09-EMER-0006,HM-TC,Modélisation des interactions entre l'hippocampe et le cortex dans « la conscience temporelle», établie à partir de l'imagerie cérébrale multimodale anatomique et fonctionnelle(2009), Colliot, Olivier, Domaines émergents - Modélisation des interactions entre l'hippocampe et le cortex dans ' la conscience temporelle', établie à partir de l'imagerie cérébrale multimodale anatomique et fonctionnelle - - HM-TC2009 - ANR-09-EMER-0006 - EMER - VALID, PaRis Artificial Intelligence Research InstitutE - - PRAIRIE2019 - ANR-19-P3IA-0001 - P3IA - VALID, Institut de Neurosciences Translationnelles de Paris - - IHU-A-ICM2010 - ANR-10-IAHU-0006 - IAHU - VALID, Experimental and theoretical investigation of the multi-scale emergence of parametric working memory in prefrontal cortex recurrent networks - - HIPLAY72016 - ANR-16-NEUC-0001 - CRCNS - VALID, Institut National de la Santé et de la Recherche Médicale (INSERM)-CHU Pitié-Salpêtrière [AP-HP], Sorbonne Université (SU)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Sorbonne Université (SU)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Sorbonne Université (SU)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Sorbonne Université (SU)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Santé et de la Recherche Médicale (INSERM)-CHU Pitié-Salpêtrière [AP-HP], Sorbonne Université (SU)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut National des Sciences Mathématiques et de leurs Interactions (INSMI)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Université de Bretagne Sud (UBS)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National de Recherche en Informatique et en Automatique (Inria)-École normale supérieure - Rennes (ENS Rennes)-Centre National de la Recherche Scientifique (CNRS)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-CentraleSupélec-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)-Université de Bretagne Sud (UBS)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-École normale supérieure - Rennes (ENS Rennes)-Centre National de la Recherche Scientifique (CNRS)-Université de Rennes 1 (UR1), Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Sorbonne Université (SU)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Sorbonne Université (SU)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Sorbonne Université (SU)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Sorbonne Université (SU)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Santé et de la Recherche Médicale (INSERM)-CHU Pitié-Salpêtrière [AP-HP], and Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Sorbonne Université (SU)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Cornu Ammonis, Focus (geometry), Computer science, 0206 medical engineering, Population, [INFO.INFO-IM] Computer Science [cs]/Medical Imaging, Biomedical Engineering, Hippocampus, 02 engineering and technology, Grey matter, Article, Diffeomorphism, Temporal lobe, Epilepsy, Atrophy, Seizures, medicine, [INFO.INFO-IM]Computer Science [cs]/Medical Imaging, Humans, Segmentation, 7-Tesla, education, education.field_of_study, medicine.diagnostic_test, business.industry, Morphometry, [SCCO.NEUR]Cognitive science/Neuroscience, [SCCO.NEUR] Cognitive science/Neuroscience, Subiculum, Magnetic resonance imaging, Pattern recognition, Ultra-high-field, medicine.disease, 020601 biomedical engineering, Magnetic Resonance Imaging, medicine.anatomical_structure, Epilepsy, Temporal Lobe, [INFO.INFO-TI] Computer Science [cs]/Image Processing [eess.IV], nervous system, [INFO.INFO-TI]Computer Science [cs]/Image Processing [eess.IV], Artificial intelligence, business, Thickness
Abstract: International audience; OBJECTIVE. 7-Tesla MRI of the hippocampus enhances the visualization of its internal substructures. Among these substructures, the cornu Ammonis and subiculum form a contiguous folded ribbon of gray matter. Here, we propose a method to analyze local thickness measurements of this ribbon. METHODS. We introduce an original approach based upon the estimation of a diffeomorphic vector field that traverses the ribbon. The method is designed to handle specificities of the hippocampus and corresponding 7-Tesla acquisitions: highly convoluted surface, non closed ribbon, incompletely defined inner/outer boundaries, anisotropic acquisitions. We furthermore propose to conduct group comparisons using a population template built from the central surfaces of individual subjects. RESULTS. We first assessed the robustness of our approach to anisotropy, as well as to inter-rater variability, on a post-mortem scan and on in vivo acquisitions respectively. We then conducted a group study on a dataset of in vivo MRI from temporal lobe epilepsy (TLE) patients and healthy controls. The method detected local thinning patterns in patients, predominantly ipsilaterally to the seizure focus, which is consistent with medical knowledge. CONCLUSION. This new technique allows measuring the thickness of the hippocampus from 7-Tesla MRI. It shows good robustness with respect to anisotropy and inter-rater variability and has the potential to detect local atrophy in patients. SIGNIFICANCE. As 7-Tesla MRI is increasingly available, this new method may become a useful tool to study local alterations of the hippocampus in brain disorders. It is made freely available to the community (code: https://github.com/aramis-lab/hiplay7-thickness, postmortem segmentation: https://doi.org/10.5281/zenodo.3533264).
Published: 2021

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