Articles: brain.
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Diffusion tensor imaging (DTI) allows the simultaneous measurement of several diffusion indices that provide complementary information on the substrate of white matter alterations in neurodegenerative diseases. These indices include fractional anisotropy (FA) as measure of fiber tract integrity, and the mode of anisotropy (Mode) reflecting differences in the shape of the diffusion tensor. We used a multivariate approach based on joint independent component analysis of FA and Mode in a large sample of 138 subjects with Alzheimer's disease (AD) dementia, 37 subjects with cerebrospinal fluid biomarker positive mild cognitive impairment (MCI-AD), and 153 healthy elderly controls from the European DTI Study on Dementia to comprehensively study alterations of microstructural white matter integrity in AD dementia and predementia AD. ⋯ Our findings suggest an early axonal degeneration in intracortical projecting fiber tracts in dementia and predementia stages of AD. An increase of Mode, parallel to an increase of FA, in the corticospinal tract suggests a more linear shape of diffusion due to loss of crossing fibers along relatively preserved cortico-petal and cortico-fugal fiber tracts in AD. Supporting this interpretation, we found three populations of fiber tracts, namely cortico-petal and cortico-fugal, commissural, and intrahemispherically projecting fiber tracts, in the peak area of parallel FA and Mode increase.
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Journal of neurotrauma · Dec 2013
Multicenter StudyUse of brain electrical activity for the identification of hematomas in mild traumatic brain injury.
This study investigates the potential clinical utility in the emergency department (ED) of an index of brain electrical activity to identify intracranial hematomas. The relationship between this index and depth, size, and type of hematoma was explored. Ten minutes of brain electrical activity was recorded from a limited montage in 38 adult patients with traumatic hematomas (CT scan positive) and 38 mild head injured controls (CT scan negative) in the ED. ⋯ Further, this was not influenced by distance of the bleed from the recording electrodes, blood volume, or type of hematoma. Distance and volume limitations noted with other methods, (such as that based on near-infrared spectroscopy) were not found, thus suggesting the TBI-Index to be a potentially important adjunct to acute assessment of head injury. Because of the life-threatening risk of undetected hematomas (false negatives), specificity was permitted to be lower, 66%, in exchange for extremely high sensitivity.
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Multicenter Study Comparative Study
Brain morphometry reproducibility in multi-center 3T MRI studies: a comparison of cross-sectional and longitudinal segmentations.
Large-scale longitudinal multi-site MRI brain morphometry studies are becoming increasingly crucial to characterize both normal and clinical population groups using fully automated segmentation tools. The test-retest reproducibility of morphometry data acquired across multiple scanning sessions, and for different MR vendors, is an important reliability indicator since it defines the sensitivity of a protocol to detect longitudinal effects in a consortium. There is very limited knowledge about how across-session reliability of morphometry estimates might be affected by different 3T MRI systems. ⋯ The average of two MPRAGE volumes acquired within each test-retest session did not systematically improve the across-session reproducibility of morphometry estimates. Our results extend those from previous studies that showed improved reliability of the longitudinal analysis at single sites and/or with non-standard acquisition methods. The multi-site acquisition and analysis protocol presented here is promising for clinical applications since it allows for smaller sample sizes per MRI site or shorter trials in studies evaluating the role of potential biomarkers to predict disease progression or treatment effects.
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J Magn Reson Imaging · Dec 2013
Multicenter Study Comparative Study Clinical TrialMulticenter measurements of myelin water fraction and geometric mean T2 : intra- and intersite reproducibility.
To assess the reproducibility of myelin water fraction (MWF) and geometric mean T2 (GMT2 ), which are in vivo markers of pathological changes underlying disability and progression in diseases such as multiple sclerosis. ⋯ MWF and GMT2 measures are reproducible between scans and across sites with an equivalent MR scanner and sequence protocol. Multicenter clinical trials using quantitative T2 relaxation are feasible.
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Multicenter Study Comparative Study
Discriminative analysis of early-stage Alzheimer's disease and normal aging with automatic segmentation technique in subcortical gray matter structures: a multicenter in vivo MRI volumetric and DTI study.
Previous studies have revealed that amyloid depositions exist in not only the hippocampus but in other subcortical gray matter structures as well. Diffusion-tensor imaging (DTI) parameters might be more sensitive measures of early degeneration in Alzheimer's disease (AD) than conventional magnetic resonance imaging (MRI) techniques. ⋯ Pathological changes takes place in the hippocampus and other subcortical gray matter structures in early-stage AD. Diffusive imaging has great diagnostic significance in early-stage AD. The combination of both imaging modalities can lead to better discrimination between early-stage AD and normal aging.