Fast multislice mapping of the myelin water fraction using multicompartment analysis of T decay at 3T: A preliminary postmortem study^†

Quantitative mapping of the myelin water content can provide significant insight into the pathophysiology of several white matter diseases, such as multiple sclerosis and leukoencephalopathies, and can potentially become a useful clinical tool for early diagnosis of these diseases. In this study, multicompartment analysis of T decay (MCAT2*) was used for the quantitative mapping of myelin water fraction (MWF). T decay of each voxel at multiple slice locations was acquired in fixed human brains using a multigradient-echo (MGRE) pulse sequence with alternating readout gradient polarities. Compared to prior techniques using Carr-Purcell-Meiboom-Gill (CPMG) acquisition, the MGRE acquisition approach has: 1) a very short first echo time (≈2 ms) and echo-spacing (≈1 ms), which allows for the acquisition of multiple sampling points during the fast decay of the myelin water signal; 2) a low RF duty cycle, which is especially important for achieving acceptable specific absorption rate (SAR) levels at high field strengths. Multicompartment analysis was then applied to the T decay in each pixel using a 3-pool model of white matter to detect the signal arising from the myelin water, myelinated axonal water, and mixed water compartments. Magn Reson Med 58:865–870, 2007. © 2007 Wiley-Liss, Inc.