Different size of T2w images and SC segmentations

[valosekj]

Just for the record, T2w SC segmentations are smaller than the original T2w images. Namely, the segmentation has fewer slices (606 vs 691):

example image

SC seg in red covers fewer slices than the background image:

@NathanMolinier is aware of this and is waiting for the new manually corrected segmentations from Yehuda.

[NathanMolinier]

Solved in #308