Quantitative Susceptibility Mapping‐Based Characterization of Lesion Heterogeneity in Multiple Sclerosis

Abstract

ABSTRACT Background Quantitative susceptibility mapping (QSM) characterizes multiple sclerosis (MS) lesions through susceptibility changes related to iron and myelin. However, the prevalence, regional distribution, and relationship of QSM‐defined lesion subtypes with choroid plexus alterations remain unclear. Purpose To characterize MS lesion subtypes using QSM and evaluate their prevalence, regional distribution, and associations with choroid plexus volume changes. Study Type Prospective longitudinal study. Population Forty‐six patients with MS (44 relapsing–remitting, 2 primary progressive; mean age, 37 ± 8 years). QSM data were available for lesion classification in 32 participants. Field Strength/Sequence 1.5T MRI with 3D T2‐FLAIR, 3D T1‐MPRAGE, and multi‐echo gradient‐echo sequences for QSM. Assessment Following whole‐brain segmentation, white matter was parcellated into periventricular, juxtacortical, and deep regions. White matter lesions were segmented using the SAMSEG algorithm and classified on QSM as isointense, hypointense, hyperintense, or paramagnetic rim lesions. Lesion counts, lesion volumes, regional distribution, and associations with choroid plexus volume changes were evaluated. Statistical Tests Normality was assessed using the Kolmogorov–Smirnov test. Spearman correlation and Mann–Whitney U tests were used. Bonferroni correction was applied for multiple comparisons. Results Eight hundred ninety lesions were identified: 512 isointense (57.1%), 65 hypointense (7.2%), 291 hyperintense (32.4%), and 29 paramagnetic rim lesions (3.2%). Isointense and hypointense lesions, potentially reflecting different stages of tissue repair, accounted for 64.3% of all lesions. Juxtacortical white matter was most frequently affected (43.4%), followed by subcortical (40.4%) and periventricular (16.2%) regions. Hyperintense lesion volume correlated significantly with baseline lesion volume ( r = 0.71), follow‐up lesion volume ( r = 0.81), and total lesion volume ( r = 0.87). Total lesion volume was significantly associated with bilateral choroid plexus volume changes ( r = 0.515–0.595). Data Conclusion QSM has the potential to characterize MS lesion heterogeneity by identifying distinct lesion susceptibility patterns. Total lesion volume was associated with choroid plexus volume changes. Evidence Level 2. Technical Efficacy Stage 2.