A5032663002- Advanced MRI Techniques and Applications
- Advanced NMR Techniques and Applications
- Atomic and Subatomic Physics Research
- Electron Spin Resonance Studies
- Advanced Neuroimaging Techniques and Applications
- Lanthanide and Transition Metal Complexes
- Medical Imaging Techniques and Applications
- Wireless Body Area Networks
- MRI in cancer diagnosis
- NMR spectroscopy and applications
- Functional Brain Connectivity Studies
- Ocean Waves and Remote Sensing
- Superconducting Materials and Applications
- Ultrasound and Hyperthermia Applications
- Radar Systems and Signal Processing
- Neural dynamics and brain function
- Mitochondrial Function and Pathology
- Epilepsy research and treatment
- Radio Frequency Integrated Circuit Design
- Advanced SAR Imaging Techniques
- Synthetic Aperture Radar (SAR) Applications and Techniques
- Microwave Imaging and Scattering Analysis
- Advanced Electron Microscopy Techniques and Applications
- Medical Image Segmentation Techniques
- Cardiac Imaging and Diagnostics
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
2015-2025
CEA Paris-Saclay
2016-2025
Université Paris-Saclay
2018-2024
Centre National de la Recherche Scientifique
2020-2024
Direction de la Recherche Fondamentale
2019-2023
Forschungszentrum Jülich
2009-2021
NeuroSpine Institute
2015-2019
Gfi Informatique (France)
2019
Resonance Research (United States)
2019
Mayo Clinic
2019
Purpose A calibration‐free parallel transmission method is investigated to mitigate the radiofrequency (RF) field inhomogeneity problem in brain imaging at 7 Tesla (T). Theory and Methods Six volunteers were scanned build a representative database of RF static maps 7T. Small‐tip‐angle inversion pulses designed with joint k T ‐points trajectory optimization work robustly on all six subjects. The returned “universal” then inserted an MPRAGE sequence implemented additional without further...
The ongoing 1000 brains study (1000BRAINS) is an epidemiological and neuroscientific investigation of structural functional variability in the human brain during aging. two recruitment sources are 10-year follow-up cohort German Heinz Nixdorf Recall (HNR) Study, HNR MultiGeneration Study cohort, which comprises spouses offspring subjects. a longitudinal cardiovascular risk factors, with comprehensive collection clinical, laboratory, socioeconomic, environmental data from population-based...
Abstract Objective To assess the possible influence of third-order shim coils on behavior gradient field and in gradient–magnet interactions at 7 T above. Materials methods Gradient impulse response function measurements were performed 5 sites spanning strengths from to 11.7 T, all them sharing same exact whole-body coil design. Mechanical fixation boundary conditions altered several ways one site study impact mechanical coupling with magnet perturbations. Vibrations, power deposition He...
Purpose Estimating tissue water content using high field MRI, such as 3 Tesla (T), is challenging due to the difficulty in dissociating radio frequency inhomogeneity pattern from signal arising intrinsic proton density (PD) variations. To overcome this problem longitudinal relaxation time T 1 can be combined with an initial guess of PD yield desired bias correction. However, it necessary know whether effects, i.e., any effect contributing while being independent hydration, influence...
Purpose T 2 ‐weighted sequences are particularly sensitive to the radiofrequency (RF) field inhomogeneity problem at ultra‐high‐field because of errors accumulated by imperfections train refocusing pulses. As parallel transmission (pTx) has proved useful counteract RF heterogeneities, universal pulses were recently demonstrated save precious time and computational efforts skipping B 1 calibration online pulse tailoring. Here, we report a design for non‐selective mitigate 7T in turbo...
Specific absorption rate (SAR) calculations in parallel transmission are commonly performed by using electromagnetic simulations on generic models. In this study, we propose a probabilistic analysis to study the safety factor employed account for SAR intersubject variability versus risk relationship head imaging at 7T.Thirty-three finite-element were conducted sample four-dimensional parameter space consisting of length, breadth, and shifts Z Y random variables. Based matrices each...
Purpose In MRI at ultra‐high field, the ‐point and spiral nonselective (SPINS) pulse design techniques can be advantageously combined with parallel transmission (pTX) universal to create uniform excitation in a calibration‐free manner. However, these approaches, duration is typically increased as compared standard hard pulses, quality regions exhibiting large resonance frequency offsets often suffer. This limitation inherent structure of or SPINS pulse, likely mitigated using...
Abstract Objective. Ultra-high field MRI with parallel transmission (pTx) provides a powerful neuroimaging tool potential application in pediatrics. The use of pTx, however, necessitates dedicated local specific absorption rate (SAR) management strategy, able to predict and monitor the peak SAR (pSAR 10g ). In this work, we address pSAR assessment for an in-house built 7 T 16Tx32Rx pediatric head coil, using concept virtual observation points (VOPs) estimation. Approach . We base our study...
Parallel transmission (pTx) technology, despite its great potential to mitigate the transmit field inhomogeneity problem in magnetic resonance imaging at ultra-high (UHF), suffers from a cumbersome calibration procedure, thereby making approach problematic for routine use. The purpose of this work is demonstrate on two different 7T systems respectively equipped with 8-transmit-channel RF coils suppliers (Rapid-Biomed and Nova Medical), benefit so-called universal pulses (UP), optimized...
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. aim this work was to compare SMS-EPI and 3D-EPI sequences terms sampling strategies for detection task-evoked activations at 7T using theory. To end, spatial temporal resolutions were matched (1.6 mm isotropic resolution, TR = 1200 ms) their excitation profiles...
To design a general framework for the optimization of an MRI protocol based on diffusion-weighted dual-echo steady-state (DW-DESS) sequence, enabling quantitative and simultaneous mapping proton density (PD), relaxation times T1 T2 diffusion coefficient D.A parameterization DW-DESS sequence minimizing Cramér-Rao lower bound each parameter estimate was proposed tested in phantom experiment. An extension implemented brain imaging to return rotationally invariant mean diffusivity (MD).In NiCl2...
Water concentration is tightly regulated in the healthy human brain and changes only slightly with age gender subjects. Consequently, water content are important for characterization of disease. MRI can be used to measure content, but as these usually low percentage range, highly accurate precise methods required detection. The method proposed here based on a long-TR (10 s) multiple-echo gradient-echo measurement an acquisition time 7:21 min. Using such long TR ensures that there no T1...
Purpose In parallel transmission (pTX), subject‐tailored RF pulses allow achieving excellent flip angle (FA) accuracy but often require computationally extensive online optimizations, precise characterization of the static field (), and transmit () distributions. This costs time requires expertise from MR user. Universal (UPs) have been proposed to reduce this burden, yet, with a penalty in FA accuracy. study introduces concept standardized universal (SUPs), where are designed offline...
Purpose Optimization of transmit array performance is crucial in ultra‐high‐field MRI scanners such as 11.7T because the increased RF losses and nonuniformity. This work presents a new workflow to investigate minimize coil losses, choose optimum configuration for imaging. Methods An 8‐channel transceiver loop‐array was simulated analyze its loss mechanism at 499.415 MHz. A folded‐end shield developed limit radiation improve efficiency. The element length, diameter length were further...
Purpose A multispoke specific absorption rate (SAR) ‐aware pulse design approach for homogeneous multiple‐slice small and large flip angle (FA) excitations with parallel transmission is proposed. The aims at optimizing in a slice‐specific manner the spokes locations radiofrequency pulses. Methods problem posed as set of magnitude‐least‐squares problems, linked together by hardware SAR constraints, solved jointly using an active‐set algorithm. Average Hamiltonian theory exploited FA case to...
Purpose A calibration‐free pulse design method is introduced to alleviate artifacts in clinical routine with parallel transmission at high field, dealing significant inter‐subject variability, found for instance the abdomen. Theory and Methods From a dual‐transmit 3T scanner, database of off‐resonance abdominal maps from 50 subjects was first divided into 3 clusters based on mutual affinity between their respective tailored k T ‐points pulses. For each cluster, computed, minimizing...
Purpose The fluid attenuated inversion recovery sequence is a pillar technique to detect brain lesions in MRI. At ultrahigh field, the lengthening of T 1 often advocates 2 ‐weighting preparation module regain signal and contrast between tissues, which can be affected by transmit RF field inhomogeneity. In this note, we report an extension previous study that now incorporates with parallel transmission calibration‐free universal pulses mitigate problem. Methods consisted 90°‐τ‐180 ° ‐τ‐90°...
Little information is available on the impact of hemodialysis cerebral water homeostasis and its distribution in chronic kidney disease. We used a neuropsychological test battery, structural magnetic resonance imaging (MRI) novel technique for quantitative measurement localized content using 3T MRI to investigate ten patients (HD) dialysis-free day after (2.4±2.2 hours), matched healthy control group with same time interval. Neuropsychological testing revealed mainly attentional executive...
Purpose To investigate the correlation between electrical conductivity and sodium concentration, both measured in vivo, human brain. Methods Conductivity measurements were performed on samples with different (Na + ) agarose concentrations using a dielectric probe, Na content was evaluated. Subsequently, brain total maps 8 healthy subjects phase‐based MREPT MRI, respectively. After co‐registration spatial normalization to 1 mm 152 MNI atlas, relationship tissue concentration (TSC) examined...
Abstract Objectives Genetic variant classification is a challenge in rare adult‐onset disorders as SCA‐PRKCG (prior spinocerebellar ataxia type 14) with mostly private conventional mutations and nonspecific phenotype. We here propose refined approach for clinicogenetic diagnosis by including protein modeling provide confirmed comprehensive phenotype description from German multi‐center cohort, standardized 3D MR imaging. Methods This cross‐sectional study prospectively obtained neurological,...
MP2RAGE parameter optimization is redefined to allow more time-efficient MR acquisitions, whereas the T1 -based synthetic imaging framework used obtain on-demand -weighted contrasts. Our aim was validate this concept on healthy volunteers and patients with multiple sclerosis, using plug-and-play parallel-transmission brain at 7 T. A "time-efficient" sequence designed optimized parameters including TI TR set as small possible. Extended phase graph formalism flip-angle values maximize...