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 T2 relaxation with multi-slice acquisitions in magnetic resonance imaging (MRI). The main advantages of using T2 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 (~2ms) and short echo spacing (~1ms), 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 3T. Five healthy adults were scanned with a multi-gradient-echo sequence to acquire T2 signal decay data. Images with a dimension of 256×256 at eight slice locations were acquired in 8.5min with a signal-to-noise ratio (SNR) of 94.8 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 sinc function. The corrected T2 signal decays were analyzed with a three-pool model to quantify MWF. Our results demonstrate the feasibility of in ivo multi-slice mapping of MWF using multi-compartmental analysis of the T2 signal decay.
Bibliographical noteFunding Information:
The authors are grateful to the insightful discussions with Jack H. Simon, MD, PhD, at Portland VA Medical Center and the assistance in data acquisition from Debra Singel at the University of Colorado Denver. This study was in part supported by the National Institutes of Health grants P50 MH079485 , R01 MH070037 and P50 MH68582 , the Department of Veterans Affairs Medical Research Service, National Multiple Sclerosis Society pilot grant PP1260 (USA) , Basic Research Program of the Korea Science and Engineering Foundation ( R01-2008-000-20270-0 ), and Yonsei Research Fund (Korea) .
All Science Journal Classification (ASJC) codes
- Cognitive Neuroscience