Comparing MRI metrics to quantify white matter microstructural damage in multiple sclerosis

Area of Science:

• Neuroimaging
• Neuroscience
• Biomedical Engineering

Background:

• Quantifying white matter damage in vivo is crucial for evaluating neuroprotective and repair strategies in multiple sclerosis (MS).
• The relationship between different MRI-based microstructural metrics and their complementary information in MS remains underexplored.

Purpose of the Study:

• To investigate the relationship and complementarity of four MRI-based microstructural metrics in different white matter tissue states in MS patients.
• To assess the sensitivity of individual metrics and their combination in quantifying white matter damage.

Main Methods:

• Acquired four microstructural metrics (fractional anisotropy, radial diffusivity, myelin water fraction, magnetisation transfer ratio) from 123 MS patients and 27 controls.
• Quantified voxel-wise damage scores in normal appearing white matter (NAWM), T2-lesions (T2L), and T1-lesions (T1L) relative to healthy tissue.
• Analyzed correlations between metrics and their sensitivity in differentiating tissue states; principal component analysis was used to combine metrics.

Main Results:

• All MRI indices indicated significant white matter damage across NAWM, T2L, and T1L, with T1L showing the greatest damage.
• Correlations between metrics ranged from 0.18 to 0.87, suggesting partial overlap but distinct information.
• Myelin water fraction (MWF) best differentiated T2L from NAWM, while magnetisation transfer ratio (MTR) best differentiated T1L from NAWM and T2L.
• Combining the four metrics did not improve sensitivity to damage compared to individual metrics.

Conclusions:

• The investigated MRI metrics are partially correlated but sensitive to different aspects of white matter pathology in MS.
• Leveraging the complementary information from these distinct metrics could enhance the assessment of therapeutic interventions in clinical trials for MS.