ABSTRACT Purpose The aim of this study is to improve the traditional T1‐weighted (T1w) over T2‐weighted (T2w) ratio as a proxy for myelin by investigating the optimal T2w TE and combination of exponent‐weighted T1w and T2w images (). Methods T1w and T2w Gradient And Spin Echo (GRASE) data were acquired from 14 volunteers, 6 of whom had a repeated GRASE scan. ratios were computed for combinations of and ranging 0–5 in steps of 0.1 and T2w GRASE TE ranging 10–160 ms. Ratios were correlated with myelin‐water fraction (MWF) maps, as a reference MRI myelin biomarker. Analyses were performed on white matter (WM) and deep gray matter (dGM). Reliability was evaluated for six subjects. Results The optimized ratio with TE , and significantly increased correlation with MWF compared to the traditional ratio (paired ‐test on Fisher‐ values, optimized , traditional , ) while preserving excellent test–retest reliability (ICC(3,1) = 0.95 for both). Conclusion The ratio associated with myelin can be improved using optimized parameters without compromising reliability. Specifically, low T2w TE can significantly increase the correlation with MWF. T1w over proton density‐weighted (T1w/PDw) metric can be a viable alternative to , more strongly associated with MWF.
Monachino et al. (Sun,) studied this question.