Issue with Level 1 and 2 When Only Part of C1 is in the Image

[yw7]

In the current implementation, we assign "1" at the top of C2 (below the superior part of C1) and "2" at the midpoint between levels 1 and 2. When only part of C1 is present in the image, this creates an issue as shown in the attached image.

To solve this:

• We can project the superior and inferior voxels of C1 as levels 1 and 2, respectively (possibly after cropping only the part of C1 that is anterior to the canal anterior-line).
• After adding brainstem segmentation as suggested in issue #48, we can put level 1 only if the brainstem is present.
• This solution will be more effective after improving the C1 ground truth segmentation, as it is currently not reliable enough for setting level 2.