# Mask volume- segment editor

**URL:** <https://discourse.slicer.org/t/mask-volume-segment-editor/7808>\
**Category:** Support\
**Created:** [July 30, 2019, 9:36am UTC](https://discourse.slicer.org/t/mask-volume-segment-editor/7808 "2019-07-30T09:36:58Z")\
**Posts on this page:** 1\
**Showing post:** 9

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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:** [July 30, 2019, 8:05pm UTC](https://discourse.slicer.org/t/mask-volume-segment-editor/7808/9 "2019-07-30T20:05:14Z")

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> [@Melanie](#):
>
> I mark my area of interest and select the option fill outside.

To keep things simple, make the segment cover the region you are interested in. Then, you can us Mask volume effect to blank out the parts outside your region of interest.

> [@Melanie](#):
>
> If I do this to an already created segment/ stl scissors can delete part of the segment.

Yes, this is correct. All effects (Scissors, Surface cut, Paint, etc.) only modify segments. They will not modify any volume nodes.

> [@Melanie](#):
>
> Then I try to register the unmasked bit of the volume with elastix.

If you blank out a region of a volume, Elastix will still take those voxels into account. This is probably not what you want.

To make Elastix ignore certain regions then you can specify masks in “Masking” section in “General registration (Elastix)” module. You can create a mask volume by using “Fill inside and outside” option in Mask volume effect.

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_[View the full topic](https://discourse.slicer.org/t/mask-volume-segment-editor/7808)._