Characterization of normal-appearing white matter in multiple sclerosis using quantitative susceptibility mapping in...

Area of Science:

• Neuroimaging
• Radiology
• Biomarker Discovery

Background:

• Quantitative susceptibility mapping (QSM) is affected by iron and myelin, complicating the interpretation of pathological changes in neurological diseases.
• Diffusion tensor imaging (DTI) provides insights into axonal and myelin integrity, offering complementary information to QSM.
• Understanding alterations in normal-appearing white matter (NAWM) is crucial for characterizing the early stages of multiple sclerosis (MS).

Purpose of the Study:

• To investigate alterations in NAWM in multiple sclerosis (MS) patients using a combined approach of QSM and DTI.
• To assess the relationship between quantitative susceptibility (QS) signals and DTI metrics (FA, RD) in NAWM.
• To explore the potential of QSM as a biomarker for MS by comparing it with established DTI measures.

Main Methods:

• Recruited 20 relapsing-remitting MS patients and 20 age-matched healthy controls (HC).
• Acquired and processed QSM, DTI (FA, RD), and R2* maps for whole-brain and specific white matter tracts.
• Compared imaging metrics between NAWM in MS patients and white matter in HC (HCWM).

Main Results:

• MS lesions showed significant differences in QS, FA, RD, and R2* compared to HCWM.
• Whole-brain NAWM did not exhibit significant differences in QSM or DTI metrics compared to HCWM.
• Specific NAWM tracts, including the cingulate gyri and forceps major, displayed discordant changes between QSM and DTI metrics, suggesting potential alterations in paramagnetic substrates like iron.

Conclusions:

• Discordant changes in QSM and DTI metrics within specific NAWM tracts in MS patients may indicate reduced iron content.
• QSM shows potential as a unique imaging biomarker for MS, offering insights beyond traditional DTI measures.
• Further validation studies are necessary to confirm the role of QSM in MS diagnosis and monitoring.