We started studying MRI of deep gray matter in MS about 10 years ago. This branched out from our interest in phase susceptibility imaging of lesions in MS. Around that time, interest in the importance of gray matter injury in MS was growing, but most gray matter work focused on the cortical layer. Our initial focus was on imaging deep gray matter using quantitative MRI methods on a 4.7T system, which was highly sensitive to iron and offered increased SNR for studying deep brain tissues that are distant from surface receive coils. We focused on susceptibility-based methods for measuring deep gray matter iron in MS, and validated quantitative methods in MS postmortem studies showed cross-sectional and longitudinal differences in healthy subjects versus those with MS and demonstrated significant correlations between MRI and disability in MS.
The current work was a natural next step, moving from generic disability scores to specific cognitive testing to determine the relevance of our deep gray matter susceptibility measures. Our future research direction is to develop more rapid and specific MRI methods that build on these techniques. In particular, we wish to gain greater specificity for iron and myelin by more carefully studying the relationships between relaxation and susceptibility measures in MS. The value of susceptibility-based imaging for potential inclusion in clinical MS exams is increasing due to an interest in central veins in lesions and smoldering lesions with active rims. Measures of deep gray matter iron could also be obtained from the same sequence. The full clinical potential of susceptibility-based MRI in MS has yet to be fully revealed and offers a wealth of future research directions.