In vivo multi-slice mapping of myelin water content using T2* decay

Quantitative assessment of the myelin water content in the brain can substantially improve our understanding of white matter diseases such as multiple sclerosis In this study, in vivo myelin water content was estimated using T-2* relaxation with multi-slice acquisitions in magnetic resonance imaging (MRI) The main advantages of using T-2* relaxation are (1) a low specific absorption rate (SAR), which is especially beneficial for imaging at high field strengths, (2) a short first-echo time (similar to 2 ms) and short echo spacing (similar to 1 ms). which allows for the acquisition of multiple sampling points during the fast decay of the myelin water signal, and (3) fast multi-slice acquisitions High-resolution and multi-slice myelin water fraction (MWF) maps were obtained in a clinically acceptable scan time at 31 Five healthy adults were scanned with a multi-gradient-echo sequence to acquire T-2* signal decay data Images with a dimension of 256 x 256 at eight slice locations were acquired in 8 5 min with a signal-to-noise ratio (SNR) of 948 in the first-echo images. The SNR was further increased by using an anisotropic diffusion filter. Local field gradients (LFG) were estimated from the acquired multi-slice data, and the LFG-induced signal decays were corrected with a first-order approximation of LFG using the sine function The corrected T-2* signal decays were analyzed with a three-pool model to quantify MWF Our results demonstrate the feasibility of in vivo multi-slice mapping of MWF using multi-compartmental analysis of the T-2* signal decay (C) 2010 Elsevier Inc All rights reserved