Abstract
PurposeValidation of quantitative MR measures for myelin imaging in the postmortem multiple sclerosis spinal cord.MethodsFour fixed spinal cord samples were imaged first with a 3T clinical MR scanner to identify areas of interest for scanning, and then with a 7T small bore scanner using a multicomponent‐driven equilibrium single‐pulse observation of T1 and T2 protocol to produce apparent proton density, T1, T2, myelin water, intracellular water, and free‐water fraction maps. After imaging, the cords were sectioned and stained with histological markers (hematoxylin and eosin, myelin basic protein, and neurofilament protein), which were quantitatively compared with the MR maps.ResultsExcellent correspondence was found between high‐resolution MR parameter maps and histology, particularly for apparent proton density MRI and myelin basic protein staining.ConclusionHigh‐resolution quantitative MRI of the spinal cord provides biologically meaningful measures, and could be beneficial to diagnose and track multiple sclerosis lesions in the spinal cord.
Highlights
The myelin sheath is an extended and modified plasma membrane wrapped around axons in a spiral fashion.[1]
The multi-echo T2 method has been previously compared to histology in post mortem brain at 1.5 T,19 and Laule et al demonstrated a strong correlation of myelin water fraction (MWF) in MS tissue samples at 7 T with luxol fast blue staining intensity for myelin on histology.[20]
A multi-component version of driven equilibrium steady-state observation of T1 and T2 has been used in clinical studies of MS,[23] primary lateral sclerosis,[24] and monitoring myelin development in children.25–29 histological validation has been lacking, and recent work has shown that mcDESPOT suffers from unpredictable bias, but as there was sufficient data for analysis, we present it here.[30,31]
Summary
The myelin sheath is an extended and modified plasma membrane wrapped around axons in a spiral fashion.[1]. Along with other related quantitative measures, including the relaxation times themselves, MWF has shown promise to identify specific features of MS pathology and monitoring disease progression.[17,18] The gold-standard method for evaluating the MWF is analysis of a multi-echo T2 relaxation curve.[16] The multi-echo T2 method has been previously compared to histology in post mortem brain at 1.5 T,19 and Laule et al demonstrated a strong correlation of MWF in MS tissue samples at 7 T with luxol fast blue staining intensity for myelin on histology.[20] These studies support the hypothesis that myelin can be mapped in the brain using MWF. To establish whether mcDESPOT could provide such an index (or indices), we undertook correlative experiments using postmortem spinal cord, to quantitatively compare MRI and histology data
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