# Wrap Solidify: How can I choose "split cavities"?

**URL:** <https://discourse.slicer.org/t/wrap-solidify-how-can-i-choose-split-cavities/26231>\
**Category:** Development\
**Tags:** segmentation, swissskullstripper\
**Created:** [November 14, 2022, 2:27pm UTC](https://discourse.slicer.org/t/wrap-solidify-how-can-i-choose-split-cavities/26231 "2022-11-14T14:27:30Z")\
**Posts on this page:** 9\
**Page:** 1

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**Author:** ![Alessia\_Giorgi](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/alessia_giorgi/32/13980_2.png) [@Alessia\_Giorgi](https://discourse.slicer.org/u/Alessia_Giorgi)\
**Post date:** [November 14, 2022, 2:27pm UTC](https://discourse.slicer.org/t/wrap-solidify-how-can-i-choose-split-cavities/26231/1 "2022-11-14T14:27:30Z")

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Hi everyone,

I’m a biomedical engineer and I’m following a project on craniostenosis.  
I’d like to share with you a doubt. I hope someone can help me.

In order to evaluate the intracranial volume, I’m using Wrap Solidify, in particular “Largest cavity” function, but I can’t understand the meaning of “Split Cavities”. How can I choose its parameter?

Thank you.

Alessia

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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 14, 2022, 3:39pm UTC](https://discourse.slicer.org/t/wrap-solidify-how-can-i-choose-split-cavities/26231/2 "2022-11-14T15:39:15Z")

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Enable split cavities if you want to remove smaller cavities that are connected to the largest cavity with a narrow neck. For example:

 ![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/a/6/a6b6d406d8382df7d7fb3b1681cd62e7a10501fe.png)

Largest cavity is the connected A-B-C cavity. Region B is connected to A with a narrowing of about 10mm. Region C is connected to A with a narrowing of about 7mm.

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**Author:** ![Alessia\_Giorgi](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/alessia_giorgi/32/13980_2.png) [@Alessia\_Giorgi](https://discourse.slicer.org/u/Alessia_Giorgi)\
**Post date:** [November 14, 2022, 4:00pm UTC](https://discourse.slicer.org/t/wrap-solidify-how-can-i-choose-split-cavities/26231/3 "2022-11-14T16:00:33Z")

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Thank you very much, now it’s clear!

If it’s possibile, I’d like to know how the algorithm of extraction works.  
What does It do at each iterations?

Thank you again!

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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 14, 2022, 6:09pm UTC](https://discourse.slicer.org/t/wrap-solidify-how-can-i-choose-split-cavities/26231/4 "2022-11-14T18:09:57Z")

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See some information here: [https://github.com/sebastianandress/Slicer-SurfaceWrapSolidify](https://github.com/sebastianandress/Slicer-SurfaceWrapSolidify)

I’ve also added some more clarifications - not merged yet but available here: [https://github.com/lassoan/Slicer-SurfaceWrapSolidify#how-it-works](https://github.com/lassoan/Slicer-SurfaceWrapSolidify#how-it-works)

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<div class="post-metadata">

**Author:** ![Alessia\_Giorgi](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/alessia_giorgi/32/13980_2.png) [@Alessia\_Giorgi](https://discourse.slicer.org/u/Alessia_Giorgi)\
**Post date:** [November 15, 2022, 9:14am UTC](https://discourse.slicer.org/t/wrap-solidify-how-can-i-choose-split-cavities/26231/5 "2022-11-15T09:14:03Z")

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Thank you!

I can’t understand this part:

 ![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/4/3/4326e0f0bb05b96491c56cef987d76a478c74864.png)  
is it inverted in what?  
why is it shrunk by the value specified in _split cavities_?

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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 15, 2022, 5:08pm UTC](https://discourse.slicer.org/t/wrap-solidify-how-can-i-choose-split-cavities/26231/6 "2022-11-15T17:08:49Z")

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> [@Alessia\_Giorgi](#):
>
> is it inverted in what?

The segmentation is inverted: filled parts become unfilled, unfilled parts become filled.

> [@Alessia\_Giorgi](#):
>
> why is it shrunk by the value specified in _split cavities_?

To make small connecting bridges between cavities disappear.

If you want to understand the algorithm then you can enable “Save intermediate results” and inspect all the outputs generated during the processing.

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<div class="post-metadata">

**Author:** ![Alessia\_Giorgi](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/alessia_giorgi/32/13980_2.png) [@Alessia\_Giorgi](https://discourse.slicer.org/u/Alessia_Giorgi)\
**Post date:** [November 16, 2022, 8:57am UTC](https://discourse.slicer.org/t/wrap-solidify-how-can-i-choose-split-cavities/26231/7 "2022-11-16T08:57:57Z")

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Thank you for your help!

Do you estimate the accuracy of the method in extracting largest cavity?

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<div class="post-metadata">

**Author:** ![Alessia\_Giorgi](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/alessia_giorgi/32/13980_2.png) [@Alessia\_Giorgi](https://discourse.slicer.org/u/Alessia_Giorgi)\
**Post date:** [November 16, 2022, 9:45am UTC](https://discourse.slicer.org/t/wrap-solidify-how-can-i-choose-split-cavities/26231/8 "2022-11-16T09:45:19Z")

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I’m sorry, but I can’t understand passages from this

 ![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/2/5/25e1516de2842605f41bb448469a717c24e4bd34.jpeg)  
to this  
 ![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/0/9/09aa1110ca22be8ea5a9512274f9ef2fe1187176.jpeg)

What did the algorithm do?

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<div class="post-metadata">

**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 21, 2022, 8:38pm UTC](https://discourse.slicer.org/t/wrap-solidify-how-can-i-choose-split-cavities/26231/9 "2022-11-21T20:38:00Z")

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It grew the segment by the specified margin.