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Distribution by Scientific Domains

Selected Abstracts

A multiparametric evaluation of regional brain damage in patients with primary progressive multiple sclerosis

Antonia Ceccarelli
Abstract The purpose of this study is to define the topographical distribution of gray matter (GM) and white matter (WM) damage in patients with primary progressive multiple sclerosis (PPMS), using a multiparametric MR-based approach. Using a 3 Tesla scanner, dual-echo, 3D fast-field echo (FFE), and diffusion tensor (DT) MRI scans were acquired from 18 PPMS patients and 17 matched healthy volunteers. An optimized voxel-based (VB) analysis was used to investigate the patterns of regional GM density changes and to quantify GM and WM diffusivity alterations of the entire brain. In PPMS patients, GM atrophy was found in the thalami and the right insula, while mean diffusivity (MD) changes involved several cortical-subcortical structures in all cerebral lobes and the cerebellum. An overlap between decreased WM fractional anisotropy (FA) and increased WM MD was found in the corpus callosum, the cingulate gyrus, the left short temporal fibers, the right short frontal fibers, the optic radiations, and the middle cerebellar peduncles. Selective MD increase, not associated with FA decrease, was found in the internal capsules, the corticospinal tracts, the superior longitudinal fasciculi, the fronto-occipital fasciculi, and the right cerebral peduncle. A discrepancy was found between regional WM diffusivity changes and focal lesions because several areas had DT MRI abnormalities but did not harbor T2-visible lesions. Our study allowed to detect tissue damage in brain areas associated with motor and cognitive functions, which are known to be impaired in PPMS patients. Combining regional measures derived from different MR modalities may be a valuable tool to improve our understanding of PPMS pathophysiology. Hum Brain Mapp 2009. 2009 Wiley-Liss, Inc. [source]

Impact of cerebrospinal fluid contamination on brain metabolites evaluation with 1H-MR spectroscopy: A single voxel study of the cerebellar vermis in patients with degenerative ataxias

Laura Guerrini MD PhD
Abstract Purpose To investigate the impact of cerebrospinal fluid (CSF) contamination on metabolite evaluation in the superior cerebellar vermis with single-voxel 1H-MRS in normal subjects and patients with degenerative ataxias. Materials and Methods Twenty-nine healthy volunteers and 38 patients with degenerative ataxias and cerebellar atrophy were examined on a 1.5 Tesla scanner. Proton spectra of a volume of interest placed in the superior vermis were acquired using a four TE PRESS technique. We calculated N-acetyl aspartate (NAA)/creatine (Cr), choline (Cho)/Cr, and NAA/Cho ratios, T2 relaxation times and concentrations of the same metabolites using the external phantom method. Finally, concentrations were corrected taking into account the proportion of nervous tissue and CSF, that was determined as Volume Fraction (VF). Results In healthy subjects, a significant difference was observed between metabolite concentrations with and without correction for VF. As compared to controls, patients with ataxias showed significantly reduced NAA/Cr and NAA concentrations, while only corrected Cr concentration was significantly increased. The latter showed an inverse correlation with VF. Conclusion CSF contamination has a not negligible effect on the estimation of brain metabolites. The increase of Cr concentration in patients with cerebellar atrophy presumably reflects the substitutive gliosis which takes place along with loss of neurons. J. Magn. Reson. Imaging 2009;30:11,17. 2009 Wiley-Liss, Inc. [source]

Improved artifact correction for combined electroencephalography/functional MRI by means of synchronization and use of vectorcardiogram recordings

Karen J. Mullinger BSc
Abstract Purpose To demonstrate that two methodological developments (synchronization of the MR scanner and electroencephalography [EEG] clocks and use of the scanner's vectorcardiogram [VCG]) improve the quality of EEG data recorded in combined EEG/functional MRI experiments in vivo. Materials and Methods EEG data were recorded using a 32-channel system, during simultaneous multislice EPI acquisition carried out on a 3 Tesla scanner. Recordings were made on three subjects in the resting state and on five subjects using a block paradigm involving visual stimulation with a 10-Hz flashing checkerboard. Results Gradient artifacts were significantly reduced in the EEG data recorded in vivo when synchronization and a TR equal to a multiple of the EEG clock period were used. This was evident from the greater attenuation of the signal at multiples of the slice acquisition frequency. Pulse artifact correction based on R-peak markers derived from the VCG was shown to offer a robust alternative to the conventionally used ECG-based method. Driven EEG responses at frequencies of up to 60 Hz due to the visual stimulus could be more readily detected in data recorded with EEG and MR scanner clock synchronization. Conclusion Synchronization of the scanner and EEG clocks, along with VCG-based R-peak detection is advantageous in removing gradient and pulse artifacts in combined EEG/fMRI recordings. This approach is shown to allow the robust detection of high frequency driven activity in the EEG data. J. Magn. Reson. Imaging 2008;27:607,616. 2008 Wiley-Liss, Inc. [source]

Gray matter deficits in young adults with narcolepsy

S. J. Kim
Objectives,,, The aim of this study was to investigate gray matter volume changes in narcolepsy. Materials and methods,,, An optimized voxel-based morphometry was conducted for 17 young adults with a sole diagnosis of human leukocyte antigen DQB1 0602 positive narcolepsy with cataplexy (26.6 5.2 years old) and 17 comparison subjects (24.6 4.9 years old) using 3 Tesla scanner. Gray matter volumes in the bilateral hypothalamic voxel of interests (VOI) were also calculated. Results,,, Compared with the comparison subjects, narcoleptic patients had gray matter volume decrease in the right hypothalamus and other regions including subcortical, prefrontal, limbic and occipital areas. Narcoleptic patients also had lower gray matter volume on predefined VOI at the bilateral hypothalamus, which correlated with the Ullanlinna Narcolepsy Scale score. Conclusions,,, Current findings suggest that narcoleptic patients have structural abnormalities in hypothalamus, which might be related to the clinical manifestation of narcolepsy with cataplexy. [source]