T1.T2product is sensitive to disability-relevant tissue damage in early relapsing-remitting multiple sclerosis

Motivation: T1w/T2w is a marker of tissue integrity in multiple sclerosis (MS), but is derived from (normalised) signal intensities, not quantitative measures. Goal(s): To determine whether longitudinal quantitative T1 and T2 and T1.T2product (directionally equivalent to T1w/T2w) measures are sensitive to disability-relevant tissue damage in early MS. Approach: Voxelwise T1.T2product maps were estimated in people recently diagnosed with relapsing-remitting MS (n=62). Longitudinal change in normal-appearing white matter (NAWM), grey matter (GM) and white matter lesions (WML), and relationship with disability, were assessed. Results: Greater increases in T1.T2product in NAWM and GM are associated with disability worsening. Impact: T1, T2 and derived T1.T2product measures are sensitive to disability-relevant tissue damage in recently diagnosed relapsing-remitting MS, and may provide greater insights into underlying pathological change than T1w/T2w intensity ratios.