Abstract
T2*-weighted multi-echo gradient-echo magnetic resonance imaging and its reciprocal R2* are used in brain imaging due to their sensitivity to iron content. In patients with multiple sclerosis who display pathological alterations in iron and myelin contents, the use of R2* may offer a unique way to untangle mechanisms of disease. Coronal slices from 8 brains of deceased multiple sclerosis patients were imaged using a whole-body 7.0 Tesla MRI scanner. The scanning protocol included three-dimensional (3D) T2*-w multi-echo gradient-echo and 2D T2-w turbo spin echo (TSE) sequences. Histopathological analyses of myelin and iron content were done using Luxol fast blue and proteolipid myelin staining and 3,3′-diaminobenzidine tetrahydrochloride enhanced Turnbull blue staining. Quantification of R2*, myelin and iron intensity were obtained. Variations in R2* were found to be affected differently by myelin and iron content in different regions of multiple sclerosis brains. The data shall inform clinical investigators in addressing the role of T2*/R2* variations as a biomarker of tissue integrity in brains of MS patients, in vivo.
Highlights
T2Ã-weighted (T2Ã-w) multi-echo gradient-echo (ME-GRE) magnetic resonance imaging (MRI) and its reciprocal R2Ã relaxation rate [R2Ã = 1/T2Ã] are sensitive to the presence of iron in tissue of normal and diseased brains [1,2,3,4,5,6,7,8,9,10]
Significant differences in R2Ã values, myelin and iron intensities were seen between several regions of interest (ROIs) as detailed below
Consistent with previous imaging studies [33, 43,44,45] in both healthy [33, 44] and diseased brains [43,44,45], we found that R2Ã values varied across brain regions of Multiple sclerosis (MS) patients and were significantly associated with both myelin and iron intensities across the brain. deep gray matter (dGM) ROIs, followed by NAWM and DWMI ROIs, displayed the highest values of R2Ã
Summary
T2Ã-weighted (T2Ã-w) multi-echo gradient-echo (ME-GRE) magnetic resonance imaging (MRI) and its reciprocal R2Ã relaxation rate [R2Ã = 1/T2Ã] are sensitive to the presence of iron in tissue of normal and diseased brains [1,2,3,4,5,6,7,8,9,10]. Iron produces T2Ã signal decay through its paramagnetic effect on susceptibility and microscopic field gradients [1,10]. This effect increases with field strength, making ME-GRE at 7.0 Tesla (7T) exquisitely sensitive for imaging iron in tissue [11,12,13].
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