Article Figures & Data
Figures
- FIG 1.
The 2D IR-UTE sequence (A) and contrast mechanism with adiabatic inversion recovery (B) and echo subtraction (C). At TI, WM signal comes only from WMS. In GM, there is a cancellation between positive GMS and negative GML longitudinal magnetizations at TI, which reduces the net transverse magnetization in GM after the excitation pulse. At the second echo, WMS and GMS signals both decay to zero or near zero, but the GML transverse magnetization is essentially unchanged. Subtraction of the second echo from the first leads to a positive signal for myelin in WM, but a negative signal for myelin in GM. This result creates very high contrast between the myelin in WM and GM (WMS = short-T2 WM, WML = long-T2 WM, GMS = short-T2 GM, GML = long-T2 GM).
- FIG 2.
MPRAGE (A, B, and C, first column) and T2-FLAIR (D, E, and F, third column) images with their corresponding NAWM maps shown to the right of them (second and fourth columns, respectively) in a healthy volunteer (a 49-year-old man: A and D, upper row), a patient with MS with an EDSS score of 2 (a 56-year-old man: B and E, middle row), and a patient with MS with an EDSS score of 6 (a 46-year-old woman: C and F, lower row).
- FIG 3.
IR-UTE images and NAWM map. These show first-echo IR-UTE images (TE = 8 µs) in the first column, second-echo images (TE = 2.3 ms) in the second column, and echo-subtraction images in the third column with the corresponding NAWM maps in the fourth column for a healthy volunteer (a 49-year-old man: A, upper row), a patient with MS with an EDSS score of 2 (a 56-year-old man: B, middle row), and a patient with MS with an EDSS score of 6 (a 46-year-old woman: C, lower row). The 2D IR-UTE images are in the native domain, which is different from the MPRAGE and T2-FLAIR images, which are in the normalized template domain.
- FIG 4.
Scatterplots and the corresponding Spearman correlations between NAWM volume and the EDSS score (A), and between lesion load and the EDSS score (B). Both NAWM volume and lesion load show only low correlations with the EDSS score (R = –0.03, P = .88, and R = 0.22, P = .24, respectively).
- FIG 5.
Mann-Whitney-Wilcoxon tests between the control (n = 14) and MS groups (n = 31) for NAWM signal on MPRAGE (A), T2-FLAIR (B), and IR-UTE (C) maps. The MPRAGE and IR-UTE maps show statistically significant differences between the 2 groups with P values of .003 and .02, respectively. The T2-FLAIR maps show no significant difference between the 2 groups (P = .23). In the boxplots, red and black horizontal lines represent median and minimum/maximum values. The upper and lower edges of the blue boxes indicate the 75th and 25th percentiles, respectively.
- FIG 6.
Scatterplots between NAWM signal and age on MPRAGE (A), T2-FLAIR (B), and IR-UTE (C) maps with the all subjects, including both the healthy controls and patients with MS. A weak correlation is seen on the MPRAGE (R = –0.10, P = .49) and T2-FLAIR (R = 0.01, P = .93) maps. The IR-UTE maps show a much larger negative correlation with the subject's age (R = –0.38, P = .009). a.u. indicates arbitrary units.
- FIG 7.
Scatterplots between NAWM signal and the EDSS scores with MPRAGE (A), T2-FLAIR (B), and IR-UTE (C) maps. Weak correlations are observed with the MPRAGE (R = –0.19, P = .31) and the T2-FLAIR (R = 0.13, P = .49) maps. The IR-UTE maps provide a larger negative correlation (R = –0.44, P = .01). A weak positive correlation is observed between the EDSS scores and patients' ages (R = 0.14, P = .44) (D). a.u. indicates arbitrary units.
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