Fig 3. Comparison of T2 activity (blue) with contrast enhancement (T1-GdDTPA, red). A, Example time profiles of a single-lesion pixel followed for 1 year. T2 activity lasts twice as long as contrast activity at this location. B, Duration distributions for contrast-enhancing lesions (red, dashed) and new T2 lesions (blue, solid), showing how many lesions (%) were active for how long (only new lesions during the first 6 weeks, as in²⁰). Dominant duration for contrast enhancement was 1 to 2 weeks (data from²⁰), whereas subacute T2 activity ranges from 3 to more than 20 weeks. The 2 populations differ significantly (P < 10^–10). Excluding subjects in the progressive group from the distribution (cyan, dashed) did not significantly affect the result. This determines that temporal changes in T2-weighted MR imaging are present long after Gd-enhancement subsides, underlining the characterization of new T2 lesion formation into acute, subacute, and chronic phases.