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Monitoring Remyelination and Its Association With Disability Improvement in Multiple Sclerosis Using APART-QSM: A
Zhuo Wang1,2, Mingsong Tang1,2, Junye Yao3
1Department of Magnetic Resonance, The Second Hospital & Clinical Medical School, Lanzhou University, Lanzhou, China.
Background:
Conventional MRI has limited specificity for myelin quantification. IterAtive magnetic suscePtibility sources sepARaTion quantitative susceptibility mapping (APART-QSM) quantifies myelin-sensitive (χdia) and iron-sensitive (χpara) susceptibility components, but its value for longitudinal assessment of remyelination in multiple sclerosis (MS) remains unclear.
Purpose:
To characterize longitudinal χdia in MS and assess its associations with clinical characteristics.
Study Type:
Prospective, longitudinal.
Population:
One hundred forty-five patients with MS and 65 healthy controls (HCs).
Field Strength/Sequence:
3.0T; 3D T1-weighted, 3D FLAIR, 3D DIR, and multi-echo gradient-echo imaging sequences.
Assessment:
APART-QSM generated χdia and χpara maps, with susceptibility quantified in lesions and non-lesional regions, and the Expanded Disability Status Scale (EDSS) assessed at baseline and follow-up.
Statistical Tests:
Chi-square, Mann-Whitney U, Wilcoxon signed-rank, Friedman tests, linear mixed-effects models, linear and nonlinear regression. A p value < 0.05 was considered significant.
Results:
One hundred one patients with MS and 20 HCs completed follow-up after a median (IQR) interval of 1.0 (0.8) and 1.25 (0.2) years, respectively. At baseline, white matter lesions (WMLs) exhibited lower χdia (0.0131 [IQR 0.0087] ppm) and higher χpara (0.0058 [IQR 0.0049] ppm) than corresponding normal-appearing white matter (NAWM) (0.0191 [0.0088] ppm; 0.0036 [0.0038] ppm; both p < 0.001). Over 1 year, χdia in WMLs increased (0.0122 [IQR 0.0069] vs. 0.0152 [IQR 0.0065] ppm, p < 0.001), particularly in ofatumumab-treated patients (0.0114 [IQR 0.0085] vs. 0.0158 [IQR 0.0081] ppm, p < 0.001). Greater increases in χdia were significantly associated with female sex, ofatumumab treatment, relapsing-remitting phenotype, and EDSS improvement (all Bonferroni correction p < 0.01). Δχdia showed a nonlinear decline with increasing disease duration (effective degrees of freedom (edf) = 1.83, p = 0.002).
Conclusion:
APART-QSM may enable longitudinal monitoring of remyelination-related changes in MS, with declining Δχdia over disease duration potentially informing individualized treatment strategies.
Stage Of Technical Efficacy:
2.
