# Design bone flap for skull

**URL:** <https://discourse.slicer.org/t/design-bone-flap-for-skull/15864>\
**Category:** Support\
**Tags:** segmentation\
**Created:** [February 5, 2021, 1:02pm UTC](https://discourse.slicer.org/t/design-bone-flap-for-skull/15864 "2021-02-05T13:02:45Z")\
**Posts on this page:** 1\
**Showing post:** 13

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**Author:** ![lassoan](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/lassoan/32/13_2.png) [@lassoan](https://discourse.slicer.org/u/lassoan)\
**Post date:** [November 11, 2021, 2:34pm UTC](https://discourse.slicer.org/t/design-bone-flap-for-skull/15864/13 "2021-11-11T14:34:12Z")

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If you have a CT image as input then then a workflow like this should work:

- Import the CT
- Create a copy of the CT (by going to right-click and click Clone)
- Mirror the CT around the LR axis by applying a transform in Transforms module that has `-1` in the top-left corner and then click the harden button to harden that transform on the volume  
 ![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/b/0/b0ab4352514fc2263628fc766a1d0e528b68fdc1.png)
- If the original and mirrored CTs are not aligned then harden the needed, align the original and the cloned image using registration method described on [this page](https://slicer.readthedocs.io/en/latest/user_guide/registration.html)
- Select the original CT as background volume (by clicking on the eye icon in Data module)
- Go to Segment Editor module
- Create a new segment, segment the skull using Threshold effect
- Click “Show 3D” button to see the bone in the 3D view
- Select the mirrored CT as master volume
- Create a new segment
- Use Threshold effect to specify editable intensity range (to limit painting to bone region)
- Select Scissors effect
- Choose Fill inside mode (so that region that are circled will be filled in the segment)
- Choose Masking / Editable area → Outside all segments (to prevent the new segment overwriting the original bone shape)
- Trace the boundary of the defect using Scissors in the 3D view

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_[View the full topic](https://discourse.slicer.org/t/design-bone-flap-for-skull/15864)._