A tissue-relaxation-dependent neighboring method for robust mapping of the myelin water fraction

作者：Kwon, Oh In; Woo, Eung Je; Du, Yiping P.; Hwang, Dosik^*

来源：NeuroImage, 2013, 74: 12-21.

DOI：10.1016/j.neuroimage.2013.01.064

• Myelin
• White matter
• T-2* relaxation
• Relaxometry
• Relaxation-dependent filtering

Quantitative assessment of the myelin content in white matter (WM) using MRI has become a useful tool for investigating myelin-related diseases, such as multiple sclerosis (MS). Myelin water fraction (MWF) maps can be estimated pixel-by-pixel by a determination of the T-2 or T-2* spectrum from signal decay measurements at each individual image pixel. However, detection of parameters from the measured decay curve, assuming a combination of smooth multi-exponential curves, results in a nonlinear and seriously ill-posed problem. In this paper, we propose a new method to obtain a stable MWF map robust to the presence of noise while sustaining sufficient resolution, which uses weighted combinations of measured decay signals in a spatially independent neighborhood to combine tissues with similar relaxation parameters. To determine optimal weighting factors, we define a spatially independent neighborhood for each pixel and a distance with respect to decay rates that effectively includes pixels with similar decay characteristics, and which therefore have similar relaxation parameters. We recover the MWF values by using optimally weighted decay curves. We use numerical simulations and in vitro and in vivo experimental brain data scanned with a multi-gradient-echo sequence to demonstrate the feasibility of our proposed algorithm and to highlight its advantages compared to the conventional method.

• 出版日期2013-7-1
• 单位浙江大学