Threshold picking up too many voxels. How do I segment different areas with same voxels without having to manually paint it?

Support
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1

Operating system: Mac
Slicer version: 4-11-0
Expected behavior:
Actual behavior:Screen Shot 2020-05-08 at 11.35.40 AM
I want to just segment the outline (cuticle) but the inner muscles are too similar in intensity and threshold keeps picking them up. How do I segment this without have to manually paint it on each z stack?

2

you can segment with the Islands after threshold.