Figure 1. Segmentation of the normal-appearing periependymal white matter.

The figure demonstrates the procedure to segment the normal-appearing periependymal white matter. First, the ventricles were segmented (A) and dilated by 1 mm to avoid partial volume effects and 2 mm to include the periependymal white matter (B). Second, the 1-mm dilated ventricle mask was subtracted from the 1 + 2 mm dilated ventricle mask (C). Finally, the periependymal mask was manually edited for smaller errors, and the lesion mask was subtracted (D) to overlay the final mask with T1 maps (E).