TY - JOUR T1 - Analysis of White Matter Damage in Patients with Multiple Sclerosis via a Novel In Vivo MR Method for Measuring Myelin, Axons, and G-Ratio JF - American Journal of Neuroradiology JO - Am. J. Neuroradiol. SP - 1934 LP - 1940 DO - 10.3174/ajnr.A5312 VL - 38 IS - 10 AU - A. Hagiwara AU - M. Hori AU - K. Yokoyama AU - M. Nakazawa AU - R. Ueda AU - M. Horita AU - C. Andica AU - O. Abe AU - S. Aoki Y1 - 2017/10/01 UR - http://www.ajnr.org/content/38/10/1934.abstract N2 - BACKGROUND AND PURPOSE: Myelin and axon volume fractions can now be estimated via MR imaging in vivo, as can the g-ratio, which equals the ratio of the inner to the outer diameter of a nerve fiber. The purpose of this study was to evaluate WM damage in patients with MS via this novel MR imaging technique.MATERIALS AND METHODS: Twenty patients with relapsing-remitting MS with a combined total of 149 chronic plaques were analyzed. Myelin volume fraction was calculated based on simultaneous tissue relaxometry. Intracellular and CSF compartment volume fractions were quantified via neurite orientation dispersion and density imaging. Axon volume fraction and g-ratio were calculated by combining these measurements. Myelin and axon volume fractions and g-ratio were measured in plaques, periplaque WM, and normal-appearing WM.RESULTS: All metrics differed significantly across the 3 groups (P < .001, except P = .027 for g-ratio between periplaque WM and normal-appearing WM). Those in plaques differed most from those in normal-appearing WM. The percentage changes in plaque and periplaque WM metrics relative to normal-appearing WM were significantly larger in absolute value for myelin volume fraction than for axon volume fraction and g-ratio (P < .001, except P = .033 in periplaque WM relative to normal-appearing WM for comparison between myelin and axon volume fraction).CONCLUSIONS: In this in vivo MR imaging study, the myelin of WM was more damaged than axons in plaques and periplaque WM of patients with MS. Myelin and axon volume fractions and g-ratio may potentially be useful for evaluating WM damage in patients with MS.AVFaxon volume fractionEDSSExpanded Disability Status ScaleMVFmyelin volume fractionNAWMnormal-appearing white matterNODDIneurite orientation dispersion and density imagingPDproton densityPWMperiplaque white matterVicvolume fraction of the intracellular compartmentVecvolume fraction of the extracellular compartmentVisovolume fraction of the CSF compartment ER -