Diffusion tensor imaging in multiple sclerosis: Longitudinal changes

Evaluation of: Harrison DM, Caffo BS, Shiee N et al.: Longitudinal changes in diffusion tensor-based quantitative MRI in multiple sclerosis. Neurology 76(2), 179-186 (2011). This article reviews the study by Harrison et al., who assessed the feasibility of diffusion tensor imaging (DTI) and magnetization transfer (MT) ratio measures as surrogates of longitudinal changes in multiple sclerosis (MS) patients in order to integrate them into clinical trials. A total of 78 patients with MS underwent a magnetic resonance examination at baseline, 3 months, 6 months and 1 year, and yearly thereafter. The magnetic resonance sequences were DTI, MT, proton density/T2-weighted, fluid-attenuated inversion recovery and T1-3D sequence (MPRAGE). The indices with the highest longitudinal variation were the supratentorial qT2 (percentage change per year = +2.0), supratentorial fractional anisotropy (percentage change per year = -0.5) and corpus callosum fractional anisotropy (percentage change per year = -1.7); MT ratio yielded measurable longitudinal changes in all of the areas studied, although at a slower rate than those yielded by DTI. With 80% power, the number of participants (per trial arm) needed for a 12- or 24-month trial were calculated using each of the MRI indices as outcome measures. The DTI indices were those that provided the smaller, more convenient numbers. Further studies are required to assess these proposed MRI parameters, and these studies will need to analyze both a more homogeneous MS population and MS patients in an early disease phase who have undergone no treatment. © 2011 Future Medicine Ltd.