1,721,032 research outputs found
Clinical applications of ultra-high field magnetic resonance imaging in multiple sclerosis.
No full textntroduction: Magnetic resonance imaging (MRI) is of paramount importance for the early diagnosis of multiple sclerosis (MS) and MRI findings are part of the MS diagnostic criteria. There is a growing interest in the use of ultra-high-field strength -7Tesla- (7T) MRI to investigate, in vivo, the pathological substrate of the disease.Areas covered: An overview of 7T MRI applications in MS focusing on increased sensitivity for lesion detection, specificity of the central vein sign and better understanding of MS pathophysiology. Implications for disease diagnosis, monitoring and treatment planning are discussed.Expert commentary: 7T MRI provides increased signal-to-noise and contrast-to-noise-ratio that allow higher spatial resolution and better detection of anatomical and pathological features. The high spatial resolution reachable at 7T has been a game changer for neuroimaging applications not only in MS but also in epilepsy, brain tumors, dementia, and neuro-psychiatric disorders. Furthermore, the first 7T device has recently been cleared for clinical use by the food and drug administration
<i>B</i> <sub>0</sub> inhomogeneity-insensitive triple-quantum-filtered sodium imaging using a 12-step phase-cycling scheme
No full textTriple-quantum-filtered (TQF) sodium MRI can be used to separate sodium NMR signals from different physiological compartments. Although three-pulse triple-quantum filtering has been demonstrated to be better suited for in vivo imaging, the absence of the refocusing pulse in the filter increases its sensitivity to magnetic field inhomogeneities. Therefore, several TQF cycles have been developed previously to correct image distortions caused by B(0) inhomogeneities. In this paper, we present a new 12-step phase-cycling TQF scheme based on three radiofrequency pulses which allows the compensation of B(0) variations both with and without ancillary B(0) map information. The method offers 40% higher signal-to-noise-ratio efficiency compared with the previously developed B(0)-correcting phase-cycling schemes
Sodium MRI of multiple sclerosis
No full textMultiple sclerosis (MS) is the most common cause of non-traumatic disability in young adults. The mechanisms underlying neurodegeneration and disease progression are poorly understood, in part as a result of the lack of non-invasive methods to measure and monitor neurodegeneration in vivo. Sodium MRI is a topic of increasing interest in MS research as it allows the metabolic characterization of brain tissue in vivo, and integration with the structural information provided by 1H MRI, helping in the exploration of pathogenetic mechanisms and possibly offering insights into disease progression and monitoring of treatment outcomes. We present an up-to-date review of the sodium MRI application in MS organized into four main sections: (i) biological and pathogenetic role of sodium; (ii) brief overview of sodium imaging techniques; (iii) results of sodium MRI application in clinical studies; and (iv) future perspectives
Progressive multiple sclerosis and gray matter pathology: An MRI perspective
No full textThe evidence suggesting a role of extensive cortical demyelization and atrophy in progressive multiple sclerosis is rapidly increasing. Although conventional magnetic resonance imaging has had a huge impact on multiple sclerosis by enabling an earlier diagnosis, and by providing surrogate markers for monitoring disease response to anti-inflammatory/immunomodulatory treatments, it is limited by the low pathological specificity and the low sensitivity to both diffuse damage in normal-appearing white matter and focal and diffuse damage in gray matter. Advanced magnetic resonance imaging techniques can partially overcome these limitations by providing markers more specific to the underlying pathologic substrates and more sensitive to the structural and functional "occult" brain tissue damage in patients with multiple sclerosis. This review describes brain and spinal cord imaging studies of multiple sclerosis with particular emphasis on gray matter imaging in both secondary progressive and primary progressive multiple sclerosis, discusses the clinical implications of gray matter damage, and outlines current magnetic resonance imaging developments at high and ultrahigh magnetic field strength. Mt Sinai J Med 78:258-267, 2011. © 2011 Mount Sinai School of Medicine
SUITer: an automated method for improving segmentation of infratentorial structures at ultra-high field MRI
No full textBackground and purpose: The advent of high and ultra-high-field MRI has significantly improved the investigation of infratentorial structures by providing high-resolution images. However, none of the publicly available methods for cerebellar image analysis has been optimized for high-resolution images yet.
Methods: We present the implementation of an automated algorithm-SUITer (spatially unbiased infratentorial for enhanced resolution) method for cerebellar lobules parcellation on high-resolution MR images acquired at both 3 and 7T MRI. SUITer was validated on five manually segmented data and compared with SUIT, FreeSurfer, and convolutional neural networks (CNN). SUITer was then applied to 3 and 7T MR images from 10 multiple sclerosis (MS) patients and 10 healthy controls (HCs).
Results: The difference in volumes estimation for the cerebellar grey matter (GM), between the manual segmentation (ground truth), SUIT, CNN, and SUITer was reduced when computed by SUITer compared to SUIT (5.56 vs. 29.23 mL) and CNN (5.56 vs. 9.43 mL). FreeSurfer showed low volumes difference (3.56 mL). SUITer segmentations showed a high correlation (R2 = .91) and a high overlap with manual segmentations for cerebellar GM (83.46%). SUITer also showed low volumes difference (7.29 mL), high correlation (R2 = .99), and a high overlap (87.44%) for cerebellar GM segmentations across magnetic fields. SUITer showed similar cerebellar GM volume differences between MS patients and HC at both 3T and 7T (7.69 and 7.76 mL, respectively).
Conclusions: SUITer provides accurate segmentations of infratentorial structures across different resolutions and MR fields
TROMBONE:<i>T</i><sub>1</sub>-relaxation-oblivious mapping of transmit radio-frequency field (<i>B</i><sub>1</sub>) for MRI at high magnetic fields
No full textLower cortical gamma-aminobutyric acid level contributes to connectivity in sensory-motor inter-connected regions in progressive MS
No full textBackground: Large-scale functional abnormalities and decreased synchronization between functionally connected regions within brain networks were reported in progressive multiple sclerosis (P-MS) patients. Low concentration of gamma-aminobutyric acid (GABA) was observed in the sensorimotor cortex (SMC) of these patients and was associated with reduced motor functions of limbs. Yet, the role of GABA in modulating functional connectivity (FC) has not been investigated in MS patients. Objectives: To determine the relationship between GABA concentration in the SMC and short-term FC changes within the sensorimotor network (SMN) in P-MS patients. Methods: Combining magnetic resonance spectroscopy (MRS) and resting-state functional MRI (rs-fMRI), we investigated the relationship between baseline GABA concentration in the left SMC and FC within SMN in P-MS patients compared to healthy controls (HCs). Additionally, we assessed the relationship between baseline GABA concentration and FC changes over a 1-year follow-up period in the patients’ group only. Results: At baseline, lower GABA levels, and decreased FC levels in regions within the SMN were observed in MS patients compared to healthy controls (HCs). Overtime, an increase in FC was observed in regions within the SMN in the MS group. This increase correlated inversely with motor performance scores. Conclusions: We postulate that in P-MS patients, lower levels of GABA in the SMC contribute to decreased inhibition, and as a result, to a reactive increase of FC in inter-connected sensorimotor brain regions, thus minimizing clinical worsening
Quantification of normal-appearing white matter tract integrity in multiple sclerosis: a diffusion kurtosis imaging study
No full textOur aim was to characterize the nature and extent of pathological changes in the normal-appearing white matter (NAWM) of patients with multiple sclerosis (MS) using novel diffusion kurtosis imaging-derived white matter tract integrity (WMTI) metrics and to investigate the association between these WMTI metrics and clinical parameters. Thirty-two patients with relapsing–remitting MS and 19 age- and gender-matched healthy controls underwent MRI and neurological examination. Maps of mean diffusivity, fractional anisotropy and WMTI metrics (intra-axonal diffusivity, axonal water fraction, tortuosity and axial and radial extra-axonal diffusivity) were created. Tract-based spatial statistics analysis was performed to assess for differences in the NAWM between patients and controls. A region of interest analysis of the corpus callosum was also performed to assess for group differences and to evaluate correlations between WMTI metrics and measures of disease severity. Mean diffusivity and radial extra-axonal diffusivity were significantly increased while fractional anisotropy, axonal water fraction, intra-axonal diffusivity and tortuosity were decreased in MS patients compared with controls (p values ranging from <0.001 to <0.05). Axonal water fraction in the corpus callosum was significantly associated with the expanded disability status scale score (ρ = −0.39, p = 0.035). With the exception of the axial extra-axonal diffusivity, all metrics were correlated with the symbol digits modality test score (p values ranging from 0.001 to <0.05). WMTI metrics are thus sensitive to changes in the NAWM of MS patients and might provide a more pathologically specific, clinically meaningful and practical complement to standard diffusion tensor imaging-derived metrics
The substrate of increased cortical FA in MS: A 7T post-mortem MRI and histopathology study
No full textUsing diffusion tensor imaging (DTI), it was previously found that demyelinated gray matter (GM) lesions have increased fractional anisotropy (FA) when compared to normal-appearing gray matter (NAGM) in multiple sclerosis (MS). The biological substrate underlying this FA change is so far unclear; both neurodegenerative changes and microglial activation have been proposed as causal contributors
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