# Segments automatically eraised when new overlapping segment added

**URL:** <https://discourse.slicer.org/t/segments-automatically-eraised-when-new-overlapping-segment-added/20921>\
**Category:** Support\
**Created:** [December 5, 2021, 10:24pm UTC](https://discourse.slicer.org/t/segments-automatically-eraised-when-new-overlapping-segment-added/20921 "2021-12-05T22:24:56Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![alan6690](https://avatars.discourse-cdn.com/v4/letter/a/bc79bd/32.png) [@alan6690](https://discourse.slicer.org/u/alan6690)\
**Post date:** [December 5, 2021, 10:24pm UTC](https://discourse.slicer.org/t/segments-automatically-eraised-when-new-overlapping-segment-added/20921/1 "2021-12-05T22:24:56Z")

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I am trying to use segment editor to create a body trunk segmentation from my CBCT images, in which I need to use logical operator to manipulate multiple segments under the same segmentation object. However, I don’t know why when I create the second segments using ‘threshold’ effect, the overlapping region between the first and second segments would be erased from the first one. How can I allow the overlapping to exist before I do the logical operation? Thank you.

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**Author:** ![mau\_igna\_06](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/mau_igna_06/32/9056_2.png) [@mau\_igna\_06](https://discourse.slicer.org/u/mau_igna_06)\
**Post date:** [December 5, 2021, 10:53pm UTC](https://discourse.slicer.org/t/segments-automatically-eraised-when-new-overlapping-segment-added/20921/2 "2021-12-05T22:53:02Z")

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Please read the “Masking” part of this document:  
[https://slicer.readthedocs.io/en/latest/user\_guide/modules/segmenteditor.html](https://slicer.readthedocs.io/en/latest/user_guide/modules/segmenteditor.html)