Myelin water imaging in multiple sclerosis: quantitative correlations with histopathology

Abstract

Various magnetic resonance (MR) techniques are used to study the pathological evolution of demyelinating diseases, such as multiple sclerosis (MS). However, few studies have validated MR derived measurements with histopathology. Here, we determine the correlation of myelin water imaging, an MR measure of myelin content, with quantitative histopathologic measures of myelin density. The multi-component T₂ distribution of water was determined from 25 formalin-fixed MS brain samples using a multi-echo T₂ relaxation MR experiment. The myelin water fraction (MWF), defined as T₂ signal below 30 milliseconds divided by the total signal, was determined for various regions of interest and compared to Luxol fast blue (myelin stain) mean optical density (OD) for each sample. MWF had a strong correlation with myelin stain [mean (range) R²-/0.67 (0.45+ 0.92)], validating MWF as a measure of myelin density. This quantitative technique has many practical applications for the in vivo monitoring of demyelination and remyelination in a variety of disorders of myelin.

Keywords

brain histopathology MRI multiple sclerosis myelin T2 relaxation

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