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209 results on '"Mauconduit, Franck"'

2. The possible influence of third-order shim coils on gradient–magnet interactions: an inter-field and inter-site study

Author

Boulant, Nicolas, Le Ster, Caroline, Amadon, Alexis, Aubert, Guy, Beckett, Alexander, Belorgey, Jean, Bonnelye, Cédric, Bosch, Dario, Brunner, David Otto, Dilasser, Guillaume, Dubois, Olivier, Ehses, Philipp, Feinberg, David, Feizollah, Sajjad, Gras, Vincent, Gross, Simon, Guihard, Quentin, Lannou, Hervé, Le Bihan, Denis, Mauconduit, Franck, Molinié, Frédéric, Nunio, François, Pruessmann, Klaas, Quettier, Lionel, Scheffler, Klaus, Stöcker, Tony, Tardif, Christine, Ugurbil, Kamil, Vignaud, Alexandre, Vu, An, and Wu, Xiaoping

Published
2024
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6. Design of calibration‐free RF pulses for T2$$ {}_2 $$‐weighted single‐slab 3D turbo‐spin‐echo sequences at 7T utilizing parallel transmission.

Author

Lowen, Daniel, Pracht, Eberhard D., Gras, Vincent, Massire, Aurelien, Mauconduit, Franck, Stoecker, Tony, and Boulant, Nicolas

Subjects
HIGH resolution imaging, BRAIN imaging, IN vivo studies, GRAPES, HOMOGENEITY
Abstract

Purpose: T 2$$ {}_2 $$‐weighted turbo‐spin‐echo (TSE) sequences are a fundamental technique in brain imaging but suffer from field inhomogeneities at ultra‐high fields. Several methods have been proposed to mitigate the problem, but were limited so far to nonselective three‐dimensional (3D) measurements, making short acquisitions difficult to achieve when targeting very high resolution images, or needed additional calibration procedures, thus complicating their application. Methods: Slab‐selective excitation pulses were designed for flexible placement utilizing the concept of k T$$ {}_T $$‐spokes. Phase‐coherent refocusing universal pulses were subsequently optimized with the Gradient Ascent Pulse Engineering algorithm and tested in vivo for improved signal homogeneity. Results: Implemented within a 3D variable flip angle TSE sequence, these pulses led to a signal‐to‐noise ratio (SNR) improvement ranging from 10% to 30% compared to a two‐dimensional (2D) T2w TSE sequence employing B1+$$ {\mathrm{B}}_1^{+} $$‐shimmed pulses. B1+$$ {\mathrm{B}}_1^{+} $$ field inhomogeneities could be mitigated and artifacts from B0$$ {\mathrm{B}}_0 $$ deviations reduced. The concept of universal pulses was successfully applied. Conclusion: We present a pulse design method which provides a set of calibration‐free universal pulses (UPs) for slab‐selective excitation and phase‐coherent refocusing in slab‐selective TSE sequences. [ABSTRACT FROM AUTHOR]

Published
2024
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7. Power deposition in the He bath induced by the Z gradient coil in the 11.7T Iseult magnet: theory versus measurements

Author

Aubert, Guy, primary, GUIHARD, Quentin, additional, Dubois, Olivier, additional, Lannou, Hervé, additional, Juster, François-Paul, additional, Belorgey, Jean, additional, Nunio, Francois, additional, Amadon, Alexis, additional, Bonnelye, Cédric, additional, Gras, Vincent, additional, Le ster, Caroline, additional, Mauconduit, Franck, additional, Vignaud, Alexandre, additional, Quettier, Lionel, additional, and Boulant, Nicolas, additional

Published
2024
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9. First in vivo images of the human brain revealed with the Iseult 11.7T MRI scanner

Author

Bihan, Denis Le, primary, Boulant, Nicolas, additional, Mauconduit, Franck, additional, Gras, Vincent, additional, Amadon, Alexis, additional, Ster, Caroline Le, additional, Luong, Michel, additional, Massire, Aurélien, additional, Pallier, Christophe, additional, Sabatier, Laure, additional, Vignaud, Alexandre, additional, and Bottlander, Michel, additional

Published
2024
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14. The restricted SAR protocol: A method to assess MRI coil prototypes in an unconditionally safe manner.

Author

Dudysheva, Natalia, Mauconduit, Franck, Abdeddaim, Redha, Gapais, Paul‐François, Hosseinnezhadian, Sajad, Dubois, Marc, Amadon, Alexis, Boulant, Nicolas, Hertz‐Pannier, Lucie, and Vignaud, Alexandre

Subjects
PROTOTYPES, MAGNETIC resonance imaging, MEDICAL protocols
Abstract

Purpose: Testing an RF coil prototype on subjects involves laborious verifications to ensure its safety. In particular, it requires preliminary electromagnetic simulations and their validations on phantoms to accurately predict the specific absorption rate (SAR). For coil design validation with a simpler safety procedure, the restricted SAR (rS) mode is proposed, enabling representative first experiments in vivo. The goal of the developed approach is to accelerate the transition of a custom coil system from prototype to clinical use. Methods: The restricted specific absorption rate (SAR) (rS) mode imposes a radical limitation on the transmitted RF power based on a worst‐case scenario of local RF power absorption. The limitations used are independent of the SAR spatial distribution, making this approach unconditionally safe. The developed rS protocol contains the sequences required for coil evaluation and satisfies the imposed rS conditions. It provides a quantitative characterization of the coil transmission and reception profiles and a qualitative evaluation of the anatomical images. Protocol validation was performed on commercial and pre‐industrial prototype coils on a small cohort of healthy volunteers. Results: The proposed rS protocol enables coil evaluation within an acquisition time compatible with common clinical protocol duration. The total time of all evaluation steps does not exceed 17 min. At the same time, the global SAR remains 100 times less than the International Electrotechnical Commission safety limit for played sequences. Conclusion: The rS protocol allows characterizing and comparing coil prototypes on volunteers without extensive electromagnetic calculations and phantom validations in an unconditionally safe way. [ABSTRACT FROM AUTHOR]

Published
2024
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15. Pushing MP2RAGE boundaries: Ultimate time‐efficient parameterization combined with exhaustive T1 synthetic contrasts.

Author

Bapst, Blanche, Massire, Aurélien, Mauconduit, Franck, Gras, Vincent, Boulant, Nicolas, Dufour, Juliette, Bodini, Benedetta, Stankoff, Bruno, Luciani, Alain, and Vignaud, Alexandre

Subjects
PARAMETERIZATION, MULTIPLE sclerosis, TIME management, SPATIAL resolution, BRAIN imaging
Abstract

Purpose: MP2RAGE parameter optimization is redefined to allow more time‐efficient MR acquisitions, whereas the T1‐based synthetic imaging framework is used to obtain on‐demand T1‐weighted contrasts. Our aim was to validate this concept on healthy volunteers and patients with multiple sclerosis, using plug‐and‐play parallel‐transmission brain imaging at 7 T. Methods: A "time‐efficient" MP2RAGE sequence was designed with optimized parameters including TI and TR set as small as possible. Extended phase graph formalism was used to set flip‐angle values to maximize the gray–to–white‐matter contrast‐to‐noise ratio (CNR). Several synthetic contrasts (UNI, EDGE, FGATIR, FLAWSMIN, FLAWSHCO) were generated online based on the acquired T1 maps. Experimental validation was performed on 4 healthy volunteers at various spatial resolutions. Clinical applicability was evaluated on 6 patients with multiple sclerosis, scanned with both time‐efficient and conventional MP2RAGE parameterizations. Results: The proposed time‐efficient MP2RAGE protocols reduced acquisition time by 40%, 30%, and 19% for brain imaging at (1 mm)3, (0.80 mm)3 and (0.65 mm)3, respectively, when compared with conventional parameterizations. They also provided all synthetic contrasts and comparable contrast‐to‐noise ratio on UNI images. The flexibility in parameter selection allowed us to obtain a whole‐brain (0.45 mm)3 acquisition in 19 min 56 s. On patients with multiple sclerosis, a (0.67 mm)3 time‐efficient acquisition enhanced cortical lesion visualization compared with a conventional (0.80 mm)3 protocol, while decreasing the scan time by 15%. Conclusion: The proposed optimization, associated with T1‐based synthetic contrasts, enabled substantial decrease of the acquisition time or higher spatial resolution scans for a given time budget, while generating all typical brain contrasts derived from MP2RAGE. [ABSTRACT FROM AUTHOR]

Published
2024
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16. Impact of B0$$ {\mathrm{B}}_0 $$ field imperfections correction on BOLD sensitivity in 3D‐SPARKLING fMRI data.

Author

Amor, Zaineb, Le Ster, Caroline, GR, Chaithya, Daval‐Frérot, Guillaume, Boulant, Nicolas, Mauconduit, Franck, Thirion, Bertrand, Ciuciu, Philippe, and Vignaud, Alexandre

Subjects
FUNCTIONAL magnetic resonance imaging, FALSE discovery rate, IMPERFECTION, OXYGEN in the blood, SIGNAL-to-noise ratio
Abstract

Purpose: Static and dynamic B0$$ {\mathrm{B}}_0 $$ field imperfections are detrimental to functional MRI (fMRI) applications, especially at ultra‐high magnetic fields (UHF). In this work, a field camera is used to assess the benefits of retrospectively correcting B0$$ {\mathrm{B}}_0 $$ field perturbations on Blood Oxygen Level Dependent (BOLD) sensitivity in non‐Cartesian three‐dimensional (3D)‐SPARKLING fMRI acquisitions. Methods: fMRI data were acquired at 1 mm3$$ {}^3 $$ and for a 2.4s‐TR while concurrently monitoring in real‐time field perturbations using a Skope Clip‐on field camera in a novel experimental setting involving a shorter TR than the required minimal TR of the field probes. Measurements of the dynamic field deviations were used along with a static ΔB0$$ \Delta {\mathrm{B}}_0 $$ map to retrospectively correct static and dynamic field imperfections, respectively. In order to evaluate the impact of such a correction on fMRI volumes, a comparative study was conducted on healthy volunteers. Results: Correction of B0$$ {\mathrm{B}}_0 $$ deviations improved image quality and yielded between 20% and 30% increase in median temporal signal‐to‐noise ratio (tSNR).Using fMRI data collected during a retinotopic mapping experiment, we demonstrated a significant increase in sensitivity to the BOLD contrast and improved accuracy of the BOLD phase maps: 44% (resp., 159%) more activated voxels were retrieved when using a significance control level based on a p‐value of 0.001 without correcting for multiple comparisons (resp., 0.05 with a false discovery rate correction). Conclusion: 3D‐SPARKLING fMRI hugely benefits from static and dynamic B0$$ {\mathrm{B}}_0 $$ imperfections correction. However, the proposed experimental protocol is flexible enough to be deployed on a large spectrum of encoding schemes, including arbitrary non‐Cartesian readouts. [ABSTRACT FROM AUTHOR]

Published
2024
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19. Impact of ∆$B_0$ field imperfections correction on BOLD sensitivity in 3D-SPARKLING fMRI data

Author

Amor, Zaineb, Le Ster, Caroline, Giliyar Radhakrishna, Chaithya, Daval-Frérot, Guillaume, Thirion, Bertrand, Boulant, Nicolas, Mauconduit, Franck, Christian, Mirkes, Ciuciu, Philippe, Vignaud, Alexandre, IFR49 - Neurospin - CEA, Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Modèles et inférence pour les données de Neuroimagerie (MIND), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Inria Saclay - Ile de France, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Siemens Healthineers [Saint-Denis], 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), Skope Magnetic Resonance Technologies AG (SKOPE), and International Society for Magnetic Resonance in Medicine

Subjects
[SPI]Engineering Sciences [physics]
Abstract

International audience; Static and dynamic ∆$B_0$ field imperfections are detrimental for fMRI applications as they degrade the temporal SNR (tSNR) and the sensitivity to the BOLD contrast. In this work we propose an experimental protocol for field imperfection monitoring and correction on 3D-SPARKLING fMRI data using the Skope Clip-on field camera in an alternative setting challenging its long TR constraint. We demonstrate the viability of our protocol and the reproducible gain in image quality, tSNR and retinotopic maps when correcting static and dynamic field imperfections on resting-state and taskbased fMRI data for 3 healthy volunteers.

Published
2023

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

Author

Baptista, Renata Porciuncula, primary, Naudin, Mathieu, additional, R, Chaithya G, additional, Daval-Frerot, Guillaume, additional, Mauconduit, Franck, additional, Haeger, Alexa, additional, Romanzetti, Sandro, additional, Lapert, Marc, additional, Ciuciu, Philippe, additional, Rabrait-Lerman, Cecile, additional, Guillevin, Remy, additional, Vignaud, Alexandre, additional, and Boumezbeur, Fawzi, additional

Published
2023
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23. Optimized interferometric encoding of presaturated TurboFLASH B1 mapping for parallel transmission MRI at 7 T: Preliminary application for quantitative T1 mapping in the spinal cord.

Author

Destruel, Aurelien, Mauconduit, Franck, Massire, Aurélien, Abdeddaim, Redha, Guye, Maxime, Gras, Vincent, and Callot, Virginie

Subjects
SPINAL cord, CERVICAL vertebrae, MAGNETIC resonance imaging, GLOBAL optimization, ENCODING
Abstract

Purpose: The acquisition of accurate B1 maps is critical for parallel transmit techniques (pTx). The presaturated turboFLASH (satTFL) method has been widely used in combination with interferometric encoding to provide robust and fast B1 maps. However, typical encodings, mostly evaluated on brain, do not necessarily fit all coils and organs. In this work, we evaluated and improved the accuracy of the satTFL for cervical spine at 7 T, proposing a novel interferometric encoding optimization. The benefits of such improvements were investigated in an exploratory study of quantitative T1 mapping with pTx‐MP2RAGE. Methods: Global optimization of interferometric encoding was implemented by simulating the ability of the satTFL to reconstruct B1 maps, with varying encoding and inclusion of complex noise, inside a region of interest covering the cervical spine. The performance of satTFL before and after optimization was compared to actual flip angle imaging. Optimized and non‐optimized B1 maps were then used to calculate pTx pulses for MP2RAGE T1 mapping. Results: Interferometric encoding optimization resulted in satTFL closer to actual flip angle imaging, with substantial gain of signal in regions where non‐optimized satTFL could fail. T1 maps measured with non‐adiabatic pTx pulses were closer to standard non‐pTx results (which used adiabatic pulses) when using optimized‐satTFL, with substantially lower specific absorption rate. Conclusion: Optimization of the satTFL interferometric encoding improves B1 maps in the spinal cord, in particular in low SNR regions. A linear correction of the satTFL was additionally shown to be required. The method was successfully used for quantitative phantom and in vivo T1 mapping, showing improved results compared to non‐optimized satTFL thanks to improved pTx‐pulse generation. [ABSTRACT FROM AUTHOR]

Published
2023
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25. Design of calibration-free RF pulses for T2-weighted single-slab 3D turbospin-echo sequences at 7T utilizing parallel transmission

Author

Löwen, Daniel, Pracht, Eberhard D., Gras, Vincent, Massire, Aurelien, Mauconduit, Franck, Boulant, Nicolas, and Stöcker, Tony

Abstract

Multi-Slice T2-weighted MR imaging is a fundamental technique in brain imaging but suffers from field inhomogeneities at ultra-high field systems. In this work we present a pulse design method which provides slab-selective universal pulses with phase-coherent excitation profiles over selected brain regions. Applied in a 3D variable flip angle turbo-spin-echo (TSE) sequence, the pulses achieve superior SNR compared to multi-slice TSE imaging and B1 + field inhomogeneity mitigation.

Published
2023
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26. Accelerated sodium MRI using undersampled 3D SPARKLING at 7T

Author

Porciuncula Baptista, Renata, Naudin, Mathieu, Giliyar Radhakrishna, Chaithya, Daval-Frérot, Guillaume, Mauconduit, Franck, Haeger, Alexa, Romanzetti, Sandro, Lapert, Marc, Ciuciu, Philippe, Rabrait-Lerman, Cécile, Guillevin, Remy, Vignaud, Alexandre, Boumezbeur, Fawzi, 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), Building large instruments for neuroimaging: from population imaging to ultra-high magnetic fields (BAOBAB), 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), Laboratoire commun Imagerie Métabolique Multi-Noyaux Multi-Organes (I3M), Université de Poitiers-Centre hospitalier universitaire de Poitiers (CHU Poitiers)-Centre National de la Recherche Scientifique (CNRS)-Siemens Healthineers, Digital Services, Digital Technology and Innovation, Data Analysis and Computations Through Imaging Modeling-Mathématiques, Imagerie, Santé (DACTIM-MIS), Laboratoire de Mathématiques et Applications (LMA-Poitiers), Université de Poitiers-Centre National de la Recherche Scientifique (CNRS)-Université de Poitiers-Centre National de la Recherche Scientifique (CNRS), Modèles et inférence pour les données de Neuroimagerie (MIND), IFR49 - Neurospin - CEA, Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Inria Saclay - Ile de France, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Siemens Healthineers [Saint-Denis], Baobab, Département PEGASE [LBBE] (PEGASE), Laboratoire de Biométrie et Biologie Evolutive - UMR 5558 (LBBE), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National de Recherche en Informatique et en Automatique (Inria)-VetAgro Sup - Institut national d'enseignement supérieur et de recherche en alimentation, santé animale, sciences agronomiques et de l'environnement (VAS)-Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National de Recherche en Informatique et en Automatique (Inria)-VetAgro Sup - Institut national d'enseignement supérieur et de recherche en alimentation, santé animale, sciences agronomiques et de l'environnement (VAS)-Centre National de la Recherche Scientifique (CNRS)-Laboratoire de Biométrie et Biologie Evolutive - UMR 5558 (LBBE), Université de Lyon-Université de Lyon-Institut National de Recherche en Informatique et en Automatique (Inria)-VetAgro Sup - Institut national d'enseignement supérieur et de recherche en alimentation, santé animale, sciences agronomiques et de l'environnement (VAS)-Centre National de la Recherche Scientifique (CNRS), Universitätsklinikum RWTH Aachen - University Hospital Aachen [Aachen, Germany] (UKA), Rheinisch-Westfälische Technische Hochschule Aachen University (RWTH), Leducq Foundation (large equipment ERPT program, 360 NEUROVASC7T project), the HPC resources of IDRIS under the allocation 2021-AD011011153 made by GENCI, European Project: 800945,NUMERICS, Ciuciu, Philippe, and International PhD programme in NUMERICal Simulation - NUMERICS - 0000-00-00 - 0000-00-00 - 800945 - VALID

Subjects
SPARKLING, [INFO.INFO-TS] Computer Science [cs]/Signal and Image Processing, [SDV.IB.IMA]Life Sciences [q-bio]/Bioengineering/Imaging, [INFO.INFO-IM] Computer Science [cs]/Medical Imaging, [SDV.NEU.SC]Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC]/Cognitive Sciences, $^{23}$Na, UHF, [SDV.IB.IMA] Life Sciences [q-bio]/Bioengineering/Imaging, [INFO.INFO-TS]Computer Science [cs]/Signal and Image Processing, [INFO.INFO-IM]Computer Science [cs]/Medical Imaging, human brain, [SDV.NEU.SC] Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC]/Cognitive Sciences, TSC, compressed sensing
Abstract

Submitted to Magnetic Resonance in Medicine; Purpose: To evaluate the benefits of SPARKLING, a stochastic k-space sampling approach over the deterministic sampling scheme TPI (Twisted Projection Imaging) in the context of accelerated cerebral $^{23}$Na MRI and assessing its impact on tissue sodium concentration (TSC) estimation.Methods: Guided by simulation results, in vitro and in vitro UTE $^{23}$Na MRI datasets were acquired at a 4 mm isotropic resolution from healthy volunteers using both TPI or SPARKLING trajectories with different acceleration factors (AF) on a 7T MR scanner equipped with a 32 channels head coil. Following reconstruction using NUFFT or Proximal Optimized Gradient Method (POGM) algorithms with or without regularization, respectively, the resulting sodium images were compared in terms of effective resolution (FWHM of the PSF), SNR and overall quality. with an in vitro assement of the accuracy of the TSC was performed via external referencing using a 4-point calibration approach. Results: In vivo cerebral sodium images acquired using SPARKLING with an acceleration factor of 32 (TA= 5 min 38 s) are similar to those obtained using TPI at AF=8 (TA= 22 min 34 s) with minimal impact on the accuracy of our TSC quantification. Conclusion: In conditions compatible with clinical examination, undersampled SPARKLING $^{23}$Na MRI can outperform the conventional TPI k-space sampling scheme allowing for shorter acquisition times.

Published
2023

27. Optimized T1 and T2 Weighted Structural Imaging on Clinical 7 Tesla Systems Employing Single Channel Universal Pulses

Author

Pracht, Eberhard Daniel, Loewen, Daniel, Lamalle, Laurent, Mauconduit, Franck, Grass, Vincent, Boulant, Nicolas, and Stöcker, Tony

Abstract

We present single channel universal pulses for optimized T1 and T2 weighted (fluid suppressed) imaging on clinical ultra high-field systems. B0 and B1 inhomogeneities are effectively mitigated, and no pulse calculations are necessary during the imaging session. Compared to a parallel transmission set-up, SAR estimation is less complex and there is no potential risk of producing a “hot-spot”, making this approach a promising tool for clinical applications such as lesion detection.

Published
2023
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28. Impact de la correction des imperfections $\Delta B_0$ sur les données IRMf collectées avec 3D-SPARKLING

Author

Amor, Zaineb, Le Ster, Caroline, Giliyar Radhakrishna, Chaithya, Daval-Frérot, Guillaume, Boulant, Nicolas, Thirion, Bertrand, Mauconduit, Franck, Mirkes, Christian, Ciuciu, Philippe, Vignaud, Alexandre, 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), Modèles et inférence pour les données de Neuroimagerie (MIND), IFR49 - Neurospin - CEA, Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Inria Saclay - Ile de France, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Siemens Healthineers [Saint-Denis], Skope Magnetic Resonance Technologies AG (SKOPE), and AMOR, Zaineb

Subjects
[SPI]Engineering Sciences [physics], [SPI] Engineering Sciences [physics]
Published
2022

30. Magnetic field strength dependent signal-to-noise ratio gain at the center of a spherical phantom and up to 11.7T

Author

Ster, Caroline Le, Grant, Andrea, Pierre-François Van De Moortele, Monreal-Madrigal, Alejandro, Adriany, Gregor, Vignaud, Alexandre, Mauconduit, Franck, Rabrait-Lerman, Cécile, Poser, Benedikt A., Kâmil Uğurbil, and Boulant, Nicolas

Subjects
signal-to-noise ratio, field strength, 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 3T and 11.7T. Methods: SNR was measured at the center of a spherical water saline phantom with a GRE sequence. Measurements were performed at NeuroSpin at 3T, 7T and 11.7T. The phantom was then shipped to Maastricht University and then to the University of Minnesota for additional data points at 7T, 9.4T and 10.5T. Experiments were carried out with the exact same type of birdcage volume coil (except at 3T 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 B01.94 ± 0.16 compared to B02.13 according to ultimate intrinsic SNR theory. Conclusion: By using quasi-identical experimental setups (RF volume coil, phantom, electrical properties and protocol), this work reports experimental data between 3T and 11.7T enabling the comparison with SNR theories where conductivity and permittivity can be assumed 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 ~32 elements for central SNR in the same spherical phantom.

Published
2022
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31. 3D-SPARKLING for functional MRI: A pilot study for retinotopic mapping at 7T

Author

Amor, Zaineb, Giliyar Radhakrishna, Chaithya, Daval-Frérot, Guillaume, Thirion, Bertrand, Mauconduit, Franck, Ciuciu, Philippe, Vignaud, Alexandre, 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), Modèles et inférence pour les données de Neuroimagerie (MIND), IFR49 - Neurospin - CEA, Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Inria Saclay - Ile de France, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Siemens Healthineers [Saint-Denis], and AMOR, Zaineb

Subjects
Retinotopic mapping, [SPI]Engineering Sciences [physics], Acquisition, Compressed Sensing, [SPI] Engineering Sciences [physics], Other - Non-Cartesian, Task-based, BOLD fMRI
Abstract

International audience

Published
2022

33. Magnetic field strength dependent SNR gain at the center of a spherical phantom and up to 11. 7T

Author

Le Ster, Caroline, primary, Grant, Andrea, additional, Van de Moortele, Pierre‐François, additional, Monreal‐Madrigal, Alejandro, additional, Adriany, Gregor, additional, Vignaud, Alexandre, additional, Mauconduit, Franck, additional, Rabrait‐Lerman, Cécile, additional, Poser, Benedikt A., additional, Uğurbil, Kâmil, additional, and Boulant, Nicolas, additional

Published
2022
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34. B0 field distortions monitoring and correction for 3D non-Cartesian fMRI acquisitions using a field camera: Application to 3D-SPARKLING at 7T

Author

Amor, Zaineb, Giliyar Radhakrishna, Chaithya, Le Ster, Caroline, Daval-Frérot, Guillaume, Boulant, Nicolas, Mauconduit, Franck, Mirkes, Christian, Ciuciu, Philippe, Vignaud, Alexandre, 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), Modèles et inférence pour les données de Neuroimagerie (MIND), IFR49 - Neurospin - CEA, Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Inria Saclay - Ile de France, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Siemens Healthineers [Saint-Denis], Skope Magnetic Resonance Technologies AG (SKOPE), European Project: 800945,NUMERICS, AMOR, Zaineb, and International PhD programme in NUMERICal Simulation - NUMERICS - 0000-00-00 - 0000-00-00 - 800945 - VALID

Subjects
[SPI]Engineering Sciences [physics], [SPI] Engineering Sciences [physics]
Abstract

International audience; The benefit of retrospective correction of static and dynamic field imperfections was studied on non-Cartesian compressed sensing-basedacquisition patterns by taking as an example 3D-SPARKLING encoding scheme. Long-TR dynamic acquisitions of T2*-weighted MRI (fMRI-like)volumes were acquired at 7T, retrospectively corrected, and the evaluation of the corrections was based on the image quality and the gain intemporal signal-to-noise ratio (tSNR). We found that correcting for the static and dynamic order contributions is enough to enhance the imagequality and tSNR significantly (up to 22% gain in median tSNR)

Published
2022

37. Reducing inter-subject variability and improving accuracy with standardised Universal Pulses

Author

Ster, Caroline Le, Mauconduit, Franck, Aur��lien Massire, Gras, Vincent, and D Nicolas Boulant

Subjects
MRI
Abstract

Synopsis Parallel transmission allows flip angle homogenization at ultra-high field. The pulse design process can be made transparent to the user with calibration-free universal pulses (UP) that are designed over a database of field maps. Here a new method is proposed where UPs are designed over a standardized database, i.e. normalized to a reference. During a scan, these standardized UPs (SUPs) are adjusted to the subject through a fast calibration that relies on a linear transformation of the actual B1+ map to the database reference. Adjusted SUPs improve excitation performance and reduce intersubject variability compared to UPs.

Published
2022
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38. Prospects of non-Cartesian 3D-SPARKLING encoding for functional MRI: A preliminary case study for retinotopic mapping

Author

Amor, Zaineb, Giliyar Radhakrishna, Chaithya, Daval-Frérot, Guillaume, Thirion, Bertrand, Mauconduit, Franck, Ciuciu, Philippe, Vignaud, Alexandre, AMOR, Zaineb, International PhD programme in NUMERICal Simulation - NUMERICS - 0000-00-00 - 0000-00-00 - 800945 - VALID, 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), Modèles et inférence pour les données de Neuroimagerie (MIND), IFR49 - Neurospin - CEA, Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Inria Saclay - Ile de France, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Siemens Healthineers [Saint-Denis], and European Project: 800945,NUMERICS

Subjects
[SPI]Engineering Sciences [physics], [SPI] Engineering Sciences [physics]
Abstract

International audience; For the first time, non-Cartesian 3D-SPARKLING (Spreading Projection Algorithm for Rapid K-space sampLING) encoding scheme was used for taskbased fMRI (retinotopic mapping) at 7T. Additionally, this new acquisition technique was compared with 3D-EPI, considered as one of the reference acquisition schemes in high-resolution fMRI. The experiment was performed on a single participant at 1mm isotropic and for a temporal resolution of 2.4s. We found that both techniques yield similar statistically significant activation patterns in the visual cortex.

Published
2022

39. 3D-SPARKLING en IRMf : Application à la rétinotopie

Author

Amor, Zaineb, Giliyar Radhakrishna, Chaithya, Daval-Frérot, Guillaume, Thirion, Bertrand, Mauconduit, Franck, Ciuciu, Philippe, Vignaud, Alexandre, AMOR, Zaineb, 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), Modèles et inférence pour les données de Neuroimagerie (MIND), IFR49 - Neurospin - CEA, Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Inria Saclay - Ile de France, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), and Siemens Healthineers [Saint-Denis]

Subjects
[SPI]Engineering Sciences [physics], [SPI] Engineering Sciences [physics]
Published
2022

41. Measuring radiofrequency field-induced temperature rise in brain MRI exams with MR thermometry and field monitoring

Author

Le Ster Caroline, Mauconduit Franck, Mirkes Christian, Vignaud Alexandre, and Boulant Nicolas

Subjects
motion compensation, MR thermometry, field monitoring
Abstract

Radiofrequency fields are ubiquitously used in Magnetic Resonance Imaging to excite water protons and form images. A non-uniform tissue temperature increase results from the balance between this power deposition and heat dissipation. Regulations impose that brain temperature should not locally exceed 39°C in normal exam conditions. Yet, because the radiofrequency field-induced temperature rise is so small, it has remained impossible to verify this safety limit in vivo on human subjects. As a result, MR practice has relied instead on electromagnetic simulations and experiments in vitro and on animals. However, anatomical and physiological differences, including anaesthesia, blur the extrapolation to humans. A methodology is introduced to measure in the brain sub-degree temperature rises with MR thermometry, field monitoring and motion compensation. Results show barely any temperature increase on awake humans with a head coil. Potential implications include improvement of human thermal models and revision of safety norms.

Published
2021
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45. Passive RF shimming for 7T head coil with hybridized meta-atom: In vivo investigation

Author

Dubois, Marc, Leroi, Lisa, Raolison, Zo, Abdeddaim, Redha, Antonakakis, Tryfon, de Rosny, Julien, Vignaud, Alexandre, Sabouroux, Pierre, Georget, Elodie, Larrat, Benoit, Tayeb, Gérard, Bonod, Nicolas, Amadon, Alexis, Mauconduit, Franck, Poupon, Cyril, Le Bihan, Denis, Enoch, Stefan, Institut FRESNEL (FRESNEL), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-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), 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), Multiwave Imaging, 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), European Project: 736937,H2020,H2020-FETOPEN-1-2016-2017,M-CUBE(2017), Centre National de la Recherche Scientifique (CNRS)-École Centrale de Marseille (ECM)-Aix Marseille Université (AMU), Assistance Publique - Hôpitaux de Marseille (APHM)-Aix Marseille Université (AMU)-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, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)

Subjects
[PHYS]Physics [physics], [SPI.ELEC]Engineering Sciences [physics]/Electromagnetism, [SDV.IB]Life Sciences [q-bio]/Bioengineering, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2020

46. 3D variable-density SPARKLING trajectories for high-resolution T2*-weighted Magnetic Resonance imaging

Author

Lazarus, Carole, Weiss, Pierre, Gueddari, Loubna, Mauconduit, Franck, Massire, Aurélien, Ripart, Mathile, Vignaud, Alexandre, Ciuciu, Philippe, Service NEUROSPIN (NEUROSPIN), 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, Modelling brain structure, function and variability based on high-field MRI data (PARIETAL), Inria Saclay - Ile de France, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Service NEUROSPIN (NEUROSPIN), 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)), PRIMO (ITAV), Institut de Mathématiques de Toulouse UMR5219 (IMT), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse 1 Capitole (UT1), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse - Jean Jaurès (UT2J)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut des Technologies Avancées en sciences du Vivant (ITAV), Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Siemens Healthineers [Saint-Denis], 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), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Inria Saclay - Ile de France, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Université Toulouse Capitole (UT Capitole), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université Toulouse - Jean Jaurès (UT2J), Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse Capitole (UT Capitole), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut des Technologies Avancées en sciences du Vivant (ITAV), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), and Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)

Subjects
3D MRI, [INFO.INFO-TS]Computer Science [cs]/Signal and Image Processing, [SDV.IB.IMA]Life Sciences [q-bio]/Bioengineering/Imaging, [INFO.INFO-IM]Computer Science [cs]/Medical Imaging, acceleration, optimization, non-Cartesian acquisition, compressed sensing, Susceptibility weighted imaging SWI
Abstract

International audience; We have recently proposed a new optimization algorithm called SPARKLING (Spreading Projection Algorithm for Rapid K-space sampLING) to design efficient Com-pressive Sampling patterns for Magnetic Resonance Imaging. This method has a few advantages over conventional non-Cartesian trajectories such as radial lines or spirals: i) it allows to sample the k-space along any arbitrary density while the other two are restricted to radial densities and ii) it optimizes the gradient waveforms for a given readout time. Here, we introduce an extension of the SPARKLING method for 3D imaging by considering both stacks-of-SPARKLING and fully 3D SPARKLING trajectories. Our method allowed to achieve an isotropic resolution of 600 µm in just 45 seconds for T2*-weighted ex vivo brain imaging at 7 Tesla over a field-of-view of 200 × 200 × 140 mm3. Preliminary human brain data shows that a stack-of-SPARKLING is less subject to off-resonance artifacts than a stack-of-spirals.

Published
2020

47. Mesures d'échauffement radiofréquence in vivo par thermométrie IRM et caméra de champ: considérations méthodologiques

Author

Le Ster, Caroline, Mauconduit, Franck, Mirkes, Christian, Bottlaender, Michel, Boumezbeur, Fawzi, Djemai, Boucif, Vignaud, Alexandre, Boulant, Nicolas, Boulant, Nicolas, Université Paris-Saclay, Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Centre National de la Recherche Scientifique (CNRS), 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), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Skope MRT, Institut National de la Santé et de la Recherche Médicale (INSERM), Service Hospitalier Frédéric Joliot (SHFJ), Unité Baobab (BAOBAB), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay

Subjects
[SDV.IB.IMA] Life Sciences [q-bio]/Bioengineering/Imaging, [SDV.BIO]Life Sciences [q-bio]/Biotechnology, [SDV.IB.IMA]Life Sciences [q-bio]/Bioengineering/Imaging, [SDV.BIO] Life Sciences [q-bio]/Biotechnology
Published
2020

48. A Statistical Robust Approach to Design Parallel Transmit Radiofrequency Excitations in MRI

Author

Gras, Vincent, Mauconduit, Franck, and Boulant, Nicolas

Subjects
Article Subject
Abstract

In MRI, at ultrahigh field, the use of parallel transmit radiofrequency (RF) arrays is very beneficial to better control spin excitation spatially. In that framework, the so-called “universal pulse” technique, proposed recently for head imaging at 7 tesla, gives access to “plug-and-play” nonadiabatic solutions exhibiting good robustness against intersubject variations in the resonant transmit fields. This new type of solution has been defined so far as the result of numerical pulse optimizations performed across a collection of RF field maps acquired on a small population sample (pulse design database). In this work, we investigate an alternative universal pulse design approach in the linear small tip angle regime whereby the database of RF field maps is first transformed into a second-order statistical model and which then exploits a statistical robust design formalism for the optimization of the RF and magnetic field gradient waveforms. Experimental validation with an eightfold transmit RF coil for 7 tesla brain imaging shows that this new approach brings some benefit in terms of computational efficiency. Hence, for a design database composed of 35 maps, the computation time initially of 50 min could be reduced down to 3 min. The proposed statistical approach thus enables integration of large databases, presumably necessary to ensure robust solutions. Finally, it provides means to compute flip angle statistics and, along with it, simple performance metrics for quality assurance (RF pulse performance) or guidance in the optimization of TX array architectures.

Published
2020
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49. Measuring radiofrequency field‐induced temperature variations in brain MRI exams with motion compensated MR thermometry and field monitoring.

Author

Le Ster, Caroline, Mauconduit, Franck, Mirkes, Christian, Vignaud, Alexandre, and Boulant, Nicolas

Subjects
RADIO frequency, THERMOMETRY, ROOT-mean-squares, MAGNETIC resonance imaging, TEMPERATURE measurements
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. [ABSTRACT FROM AUTHOR]

Published
2022
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