1. A method for early detection of white matter abnormality in the central nervous system comprising the steps of: acquiring free induction decay signals of a plurality of voxels at multiple slice locations in the central nervous system using an echo-planar spectroscopic imaging pulse sequence; and analyzing the free induction decay signals in a plurality of pixels corresponding to the plurality of voxels to obtain a quantitative map of myelin water fraction in the central nervous system using multi-compartment analysis.