Utility of a Multiparametric Quantitative MRI Model That Assesses Myelin and Edema for Evaluating Plaques, Periplaque White Matter, and Normal-Appearing White Matter in Patients with Multiple Sclerosis: A Feasibility Study

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Fig 1.
Representative images of a 27-year-old woman with multiple sclerosis. Panels show a synthetic T2-weighted image (A), a conventional T2-weighted image (B), and maps of myelin partial volume (C), excess parenchymal water partial volume (D), R1 (E), R2 (F), and PD (G). Two plaques are shown by arrows on the T2-weighted images (A and B). On the V_EPW map (D), the periphery of the plaque adjacent to the trigone of the right ventricle (arrow) is visible but the one adjacent to the anterior horn of the left ventricle is not. The V_EPW of this invisible plaque was very low but still higher than that of NAWM. The red intracranial outline is displayed for visual guidance in tissue images (C and D).
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Fig 2.
Magnified images of Fig 1A. The upper 2 panels show the same synthetic T2-weighted image without (A) or with (B) placement of ROIs. An ROI (black arrow) was drawn on a plaque adjacent to the left anterior horn, and 3 ROIs (arrowheads) were placed on periplaque white matter to encircle the plaque. The fourth ROI on PWM was discarded because it overlapped the CSF. The ROI of the plaque was copied and pasted onto the contralateral normal-appearing white matter (white arrow). These ROIs were then copied and pasted onto each quantification map. A map of the corresponding myelin partial volume (C) is shown as an example.

Table 1:

Descriptive values of plaques, periplaque white matter, and normal-appearing white matter^{^a}

	V_MY (%)	V_EPW (%)	R1 (s⁻¹)	R2 (s⁻¹)	PD (%)
Plaques	12.59 ± 6.66	5.82 ± 4.75	0.90 ± 0.20	10.88 ± 1.41	78.86 ± 6.35
PWM	29.29 ± 3.73	2.31 ± 2.38	1.31 ± 0.13	13.14 ± 0.77	68.09 ± 2.49
NAWM	32.88 ± 3.12	0.92 ± 1.90	1.40 ± 0.08	13.85 ± 0.97	63.97 ± 2.07

Table 2:

Percentage changes of V_MY, V_EPW, R1, R2, and PD in plaques and periplaque white matter relative to normal-appearing white matter^{^a}

	V_MY (%)	V_EPW (%)	R1 (%)	R2 (%)	PD (%)
Plaques	−61.59 ± 20.28^{^b}	13.82 × 10³ ± 49.47 × 10^{3^b}	−35.23 ± 13.93^{^b}	−21.06 ± 11.39^{^b}	23.37 ± 10.30^{^b}
PWM	−10.51 ± 11.41^{^c}	51.33 × 10² ± 155.31 × 10^{2^c}	−6.08 ± 8.66^{^c}	−4.79 ± 6.79^{^c}	3.37 ± 4.24^{^b}

↵a Values are mean ± SD. Of the 135 ROIs, 39 were discarded after calculating the percentage change of V_EPW relative to NAWM because the V_EPW of these ROIs was equivalent to zero in NAWM.
↵b P < .001 in the percentage change for plaques relative to NAWM for comparison between each pair of metrics, except between R2 and PD (P = .31). Statistical analysis was performed for absolute values.
↵c P < .001 in the percentage change for PWM relative to NAWM between V_EPW and other metrics, and between V_MY and R2 or PD, P < .05 between V_MY and R1, and P > .05 between R2 and R1 (.31) or PD (.30). Statistical analysis was performed for absolute values.