Myelin Water Imaging: Implementation and Development at 3.0T and Comparison to 1.5T Measurements

Multicomponent T(2) relaxation imaging can be used to measure signal from water trapped between myelin bilayers; the ratio of myelin water signal to total water is termed the myelin water fraction (MWF). The goal of this study was to implement and develop the single-slice T(2)-imaging technique proposed by Poon and Henkelman. For refinement, scan parameters (gradient crusher height and slew rate, bandwidth, echo spacing, matrix size, repetition time, and phase rewinding) were varied in water-based phantoms and in fixed and in vivo brain. Changes in the standard deviation of the residuals of the multiexponential fit, MWF, T(2), and peak width of the intra/extracellular water were monitored to determine which scan parameters minimized artifacts. Subsequently, we compared multicomponent T(2) measurements at 1.5T and 3.0T for 10 healthy volunteers, and investigated the differences in SNR, fit residuals, MWF, and T(2) and peak width of the intra/extracellular water, at higher magnetic field. MWF maps were found to be qualitatively similar between field strengths. MWFs were found to be significantly higher at 3.0T than at 1.5T, but with a strongly significant correlation between measurements [R(2) > 0.92, P < 0.0005). The signal-to-noise ratio (SNR) was nearly double at 3.0T, but the standard deviation of residuals was increased in most cases. Magn Reson Med 62:106-115,2009. (C) 2009 Wiley-Liss, Inc.