![]() Overall, our findings indicated a high degree of correlation (but not equivalence) between FSE- based and GRASE- based T 1 w/ T 2 w ratios, and low correlations between T 1 w/ T 2 w ratios and MWFs. However, correlations between either FSE- based or GRASE- based T 1 w/ T 2 w ratios and MWFs were extremely low in WM structures (FSE- based, r 2 = 0.000020 GRASE- based, r 2 = 0.0014), low across all ROIs (FSE- based, r 2 = 0.053 GRASE- based, r 2 = 0.029) and moderate in SGM structures (FSE- based, r 2 = 0.20 GRASE- based, r 2 = 0.17). Although the GRASE sequence systematically underestimated T 1 w/ T 2 w values compared to the FSE sequence (revealed by Bland-Altman and mountain plots), linear regressions across participants and ROIs revealed consistently high correlations between the two methods (r 2 = 0.62 for all ROIs, r 2 = 0.62 for WM structures and r 2 = 0.73 for SGM structures). Then, after high-dimensional, non-linear warping, region of interest (ROI) analyses were performed to compare T 1 w/ T 2 w ratios and MWF estimates (across participants and brain regions) in 11 bilateral white matter (WM) and four bilateral subcortical grey matter (SGM) structures extracted from the JHU_MNI_SS 'Eve' atlas. In order to compare these measurements across a relatively wide range of myelin concentrations, whole-brain T 1 w magnetization prepared rapid acquisition gradient echo (MPRAGE), T 2 w FSE and three-dimensional multi-echo GRASE data were acquired from 10 participants with multiple sclerosis at 3 T. Given the growing popularity of T 1 -weighted/ T 2 -weighted ( T 1 w/ T 2 w) ratio measurements, the objective of the current study was to evaluate the concordance between T 1 w/ T 2 w ratios obtained using conventional fast spin echo (FSE) versus combined gradient and spin echo (GRASE) sequences for T 2 w image acquisition, and to compare the resulting T 1 w/ T 2 w ratios with histologically validated myelin water fraction (MWF) measurements in several subcortical brain structures. ![]() Uddin, Md Nasir Figley, Teresa D Marrie, Ruth Ann Figley, Chase R Temperature dependent solvent extraction studies allowed for determination of thermodynamic extraction constants and ΔH and ΔS parameters for themore » corresponding extractive processes.« lessĬan T1 w/ T 2 w ratio be used as a myelin-specific measure in subcortical structures? Comparisons between FSE- based T1 w/ T 2 w ratios, GRASE- based T1 w/ T 2 w ratios and multi-echo GRASE- based myelin water fractions.
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