Correlates of MS disability assessed in vivo using aggregates of MR quantities

Objectives: To assess the magnitude of the correlations between disability and composite MRI scores in patients with MS. Methods: T2- and T1-weighted MRI, magnetization transfer imaging, diffusion tenser imaging, and MRS imaging scans of the brain from 23 patients with MS were obtained. T2 lesion volume, T1 lesion volume, brain magnetization transfer ratio, average brain diffusivity ((D) over bar), and brain,N-acetylaspartate/creatine ratio were measured. Results: The correlations between the Expanded Disability Status Scale (EDSS) score and each of the MR quantities taken in isolation were not significant, with the exception of the correlation between EDSS and the NAA/creatine ratio (r = -0.50; p = 0.01). In contrast, three of the composite MR scores computed using regression models were strongly correlated with the EDSS scores (r range, 0.58 to 0.73; p range, 0.004 to 0.0001). The model that included T2 and T1 lesion volumes and brain (D) over bar explained 34% of the EDSS variance; the model that included T2 and T1 lesion volumes and brain N-acetylaspartate/creatine ratio explained 36% of the EDSS variance; the model that included T1 lesion volume, brain (D) over bar, and brain N-acetylaspartate/creatine ratio explained 53% of the EDSS variance. Conclusions: The results suggest that multiparametric MR models have the potential to provide powerful measures to monitor MS evolution.