Figure 2: An axial section of T2-FLAIR (A), T1-Post (B and C) and T1-Pre (D and E) image showing a typical ring-enhanced lesion, its corresponding ROIs and the spatial relationship between active andT1-hypointense lesion. A hyperintense spot observed on T2- FLAIR image (red arrowhead in A) may represent a ring-enhanced lesion on T1-Post image (red arrowheads in B and C). It should be noted that remarkable T1 signal loss occurred inside the enhanced ring (E). The entire lesion area was then divided into two regions, T1-enhanced (C, the area encompassed by two red tracks) and T1- hypointense (C, the rest central part encompassed by the smaller red track) regions. Just like the ring-enhanced region surrounding the hypointense area, some active lesions appeared immediately adjacent to the T1-hypointense lesions (comparing the locations of enhanced regions indicated by yellow arrowheads in B and the locations of hypointense areas indicated by blue arrowheads in D).