Publications by authors named "Jean Philippe Ranjeva"

Purpose: 7T MRI imaging of the pituitary gland is an emerging technique. The purpose of this article is to review the current status of the 7T MRI of the pituitary gland, particularly in the context of pituitary microadenoma pathology. We will discuss technical challenges and parallel transmission opportunities.

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Objective: Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by significant heterogeneity among patients. 23Na MRI maps abnormal sodium homeostasis that reflects metabolic alterations and energetic failure contributing to the neurodegenerative process. In this study, we investigated disease severity at the individual level in ALS patients using brain 23Na MRI.

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Patients presenting with drug-resistant epilepsy are eligible for surgery aiming to remove the regions involved in the production of seizure activities, the so-called epileptogenic zone network (EZN). Thus the accurate estimation of the EZN is crucial. Data-driven, personalized virtual brain models derived from patient-specific anatomical and functional data are used in Virtual Epileptic Patient (VEP) to estimate the EZN via optimization methods from Bayesian inference.

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Whole-brain functional connectivity networks (connectomes) have been characterized at different scales in humans using EEG and fMRI. Multimodal epileptic networks have also been investigated, but the relationship between EEG and fMRI defined networks on a whole-brain scale is unclear. A unified multimodal connectome description, mapping healthy and pathological networks would close this knowledge gap.

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Objectives: Compelling evidence indicates a significant involvement of cortical lesions in the progressive phase of multiple sclerosis (MS), significantly contributing to late-stage disability. Despite the promise of ultra-high-field magnetic resonance imaging (MRI) in detecting cortical lesions, current evidence falls short in providing insights into the existence of such lesions during the early stages of MS or their underlying cause. This study delineated, at the early stage of MS, (1) the prevalence and spatial distribution of cortical lesions identified by 7 T MRI, (2) their relationship with white matter lesions, and (3) their clinical implications.

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  • This study explores biomarkers of cellular dysfunction in early Parkinson's disease (ePD) to aid in developing targeted therapies.
  • Researchers scanned 12 ePD patients and 13 healthy controls using advanced MRI techniques to assess brain sodium levels, microstructural changes, and iron deposition.
  • The results showed higher sodium concentrations in specific brain regions of ePD patients, suggesting potential new therapeutic directions that should be investigated further.
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Background: Progression independent of relapse activity (PIRA) has been described since the early stage of relapsing multiple sclerosis (RMS). However, little is known about the relation between PIRA and inflammatory activity that is particularly important at this stage of the disease.

Method: We included 110 patients in a prospective study within 18 months of RMS onset.

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  • The study investigates how atrophy in the brain and upper cervical spinal cord relates to the severity of amyotrophic lateral sclerosis (ALS).
  • Researchers analyzed 29 ALS patients and 24 healthy controls, measuring brain and spinal cord volumes using MRI to differentiate between fast and slow progressors based on functional rating scales.
  • Results showed that fast progressors experienced more significant atrophy in brain grey matter and spinal structures compared to healthy controls and slow progressors, indicating that this atrophy could serve as a biomarker for ALS disease progression.
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Focal epilepsy is characterized by repeated spontaneous seizures that originate from cortical epileptogenic zone networks (EZN). Analysis of intracerebral recordings showed that subcortical structures, and in particular the thalamus, play an important role in seizure dynamics as well, supporting their structural alterations reported in the neuroimaging literature. Nonetheless, between-patient differences in EZN localization (e.

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Purpose: To demonstrate the bias in quantitative MT (qMT) measures introduced by the presence of dipolar order and on-resonance saturation (ONRS) effects using magnetization transfer (MT) spoiled gradient-recalled (SPGR) acquisitions, and propose changes to the acquisition and analysis strategies to remove these biases.

Methods: The proposed framework consists of SPGR sequences prepared with simultaneous dual-offset frequency-saturation pulses to cancel out dipolar order and associated relaxation (T ) effects in Z-spectrum acquisitions, and a matched quantitative MT (qMT) mathematical model that includes ONRS effects of readout pulses. Variable flip angle and MT data were fitted jointly to simultaneously estimate qMT parameters (macromolecular proton fraction [MPF], T , T , R, and free pool T ).

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Background: To investigate the association of ihMT (inhom signals with the demyelination and remyelination phases of the acute cuprizone mouse model in comparison with histology, and to assess the extent of tissue damage and repair from MRI data.

Methods: Acute demyelination by feeding 0.2% cuprizone for five weeks, followed by a four-week remyelination period was applied on genetically modified plp-GFP mice.

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Whole brain ionic and metabolic imaging has potential as a powerful tool for the characterization of brain diseases. We combined sodium MRI ( Na MRI) and H-MR Spectroscopic Imaging ( H-MRSI), assessing changes within epileptogenic networks in comparison with electrophysiologically normal networks as defined by stereotactic EEG (SEEG) recordings analysis. We applied a multi-echo density adapted 3D projection reconstruction pulse sequence at 7 T ( Na-MRI) and a 3D echo-planar spectroscopic imaging sequence at 3 T ( H-MRSI) in 19 patients suffering from drug-resistant focal epilepsy who underwent presurgical SEEG.

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Rugby players are subject to multiple impacts to their head and neck that could have adverse neurological effects and put them at increased risk of neurodegeneration. Previous studies demonstrated altered default mode network and diffusion metrics on brain, as well as more foraminal stenosis, disc protrusion and neck pain among players of contact sports as compared to healthy controls. However, the long-term effects of practice and repetitive impacts on brain and cervical spinal cord (cSC) of the rugby players have never been systematically investigated.

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Objective: Quantification of brain injury in patients with variable disability despite similar disease duration may be relevant to identify the mechanisms underlying disability in multiple sclerosis (MS). We aimed to compare grey-matter sodium abnormalities (GMSAs), a parameter reflecting neuronal and astrocyte dysfunction, in MS patients with benign multiple sclerosis (BMS) and non-benign multiple sclerosis (NBMS).

Methods: We identified never-treated BMS patients in our local MS database of 1352 patients.

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Purpose: Ultra-high field H MR spectroscopy (MRS) is of great interest to help characterizing human spinal cord pathologies. However, very few studies have been reported so far in this small size structure at these fields due to challenging experimental difficulties caused by static and radiofrequency field heterogeneities, as well as physiological motion. In this work, in line with the recent developments proposed to strengthen spinal cord MRS feasibility at 7 T, a respiratory-triggered acquisition approach was optimized to compensate for dynamic B field heterogeneities and to provide robust cervical spinal cord MRS data.

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Hypothalamus (HT), this small structure often perceived through the prism of neuroimaging as morphologically and functionally homogeneous, plays a key role in the primitive act of feeding. The current paper aims at reviewing the contribution of magnetic resonance imaging (MRI) in the study of the role of the HT in food intake regulation. It focuses on the different MRI techniques that have been used to describe structurally and functionally the Human HT.

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We present a new consensus atlas of deep grey nuclei obtained by shape-based averaging of manual segmentation of two experienced neuroradiologists and optimized from 7T MP2RAGE images acquired at (.6 mm) in 60 healthy subjects. A group-wise normalization method was used to build a high-contrast and high-resolution T -weighted brain template (.

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Article Synopsis
  • Amygdala enlargement is linked to drug-resistant temporal lobe epilepsy, but its role in epilepsy and psychiatric conditions is still unclear.
  • A study of 12 patients found that the enlarged amygdala often coincided with the epileptogenic zone and correlated with psychiatric disorders like anxiety and depression.
  • The findings suggest that amygdala enlargement may result from stress-related changes in brain networks and is associated with complex networks in drug-resistant epilepsy cases.
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Purpose: To minimize the sensitivity of inhomogeneous magnetization transfer gradient-echo (ihMT-GRE) imaging to radiofrequency (RF) transmit field ( ) inhomogeneities at 3 T.

Methods: The ihMT-GRE sequence was optimized by varying the concentration of the RF saturation energy over time, obtained by increasing the saturation pulse power while extending the sequence repetition time (TR). Different protocols were tested using numerical simulations and human in vivo experiments in the brain white matter (WM) of healthy subjects at 3 T.

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Pathophysiology of idiopathic Parkinson's disease (iPD) is complex and still misunderstood. At a time when treatments with disease-modifying potential are being developed, identification of early markers of neurodegeneration is essential. Intracerebral sodium accumulation could be one of them.

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  • This study compares three techniques for single-voxel proton cardiovascular magnetic resonance spectroscopy (H-CMRS) at 3 T—PRESS, sLASER, and STEAM—to accurately quantify intramyocardial fatty acids and creatine in the heart.
  • Using a specially designed phantom and in vivo testing on 10 healthy subjects, the research finds that sLASER showed the least bias in fat-to-water ratios, while PRESS had the best signal-to-noise ratio for free-breathing scans.
  • Overall, while sLASER had better correlations for creatine measurements compared to PRESS, STEAM was the least effective, especially for creatine quantification, and all methods suffered
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Although multiple sclerosis (MS) is frequently accompanied by visuo-cognitive impairment, especially functional brain mechanisms underlying this impairment are still not well understood. Consequently, we used a functional MRI (fMRI) backward masking task to study visual information processing stratifying unconscious and conscious in MS. Specifically, 30 persons with MS (pwMS) and 34 healthy controls (HC) were shown target stimuli followed by a mask presented 8-150 ms later and had to compare the target to a reference stimulus.

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This manuscript reviews the contributions of the neuroimaging methods including PET, conventional and advanced MRI methods to monitor the effect of new disease modifying drugs in neurodegenerative diseases. It now seems obvious that in many pathologies these two techniques are more and more complementary.

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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.

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Brain vascular damage accumulate in aging and often manifest as white matter hyperintensities (WMHs) on MRI. Despite increased interest in automated methods to segment WMHs, a gold standard has not been achieved and their longitudinal reproducibility has been poorly investigated. The aim of present work is to evaluate accuracy and reproducibility of two freely available segmentation algorithms.

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