In-vivo multi-exponential T-2, magnetization transfer and quantitative histology in a rat model of intramyelinic edema

Two MRI methods, multi-exponential analysis of transverse relaxation (META and quantitative magnetization transfer (qMT), were used along with quantitative evaluation of histology in a study of intra-myelinic edema in rat spinal while matter. The results showed a strong linear correlation between a distinct long-T-2 signal from MET, analysis and the edema water volume fraction as measured by histology, although this analysis overestimated the edema water content by approximate to 100% relative to quantitative histological measurements. This overestimation was reasoned to result from the effects of inter-compartmental water exchange on observed transverse relaxation. Commonly studied MRI markers for myelin, the myelin water fraction (from MET, analysis) and the macromolecular pool size ratio (from qMT analysis) produced results that could not be explained purely by changes in myelin content. The results demonstrate the potential for MET, analysis as well as the limits of putative myelin markers for characterizing white matter abnormalities involving intra-myelinic edema. (C) 2013 The Authors. Published by Elsevier Inc. Open access under CC BY license.