# How volume rendering erase or hide some small objects?

**URL:** <https://discourse.slicer.org/t/how-volume-rendering-erase-or-hide-some-small-objects/19427>\
**Category:** Support\
**Tags:** volume-rendering\
**Created:** [August 31, 2021, 9:17am UTC](https://discourse.slicer.org/t/how-volume-rendering-erase-or-hide-some-small-objects/19427 "2021-08-31T09:17:22Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![StephenLeePeng](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/stephenleepeng/32/11892_2.png) [@StephenLeePeng](https://discourse.slicer.org/u/StephenLeePeng)\
**Post date:** [August 31, 2021, 9:17am UTC](https://discourse.slicer.org/t/how-volume-rendering-erase-or-hide-some-small-objects/19427/1 "2021-08-31T09:17:22Z")

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When I load a CT-Chest volume with a lung nodule inside, I want to crop a region contain the lung nodule, and rendering volume to display the nodule and the vessel arround the nodule.

The problem is, when I adjust shift slider, Scalar Opacity Mapping, or some other parameters, volume rendering result is not ideal. When I set the lower threshold too much, some more small, discontinuous objects will appear, when I set the lower threshold too high, some small, may important vessel will disappear.

When I asked the Radiology doctors, they say there exist a button or module in their PACS postprocess workstation, can erase some small tiny objects in the volume rendering result.

So I want to know, is there exist a module similar to above description to realize the effect to clear those some tiny objects.

As follow is a volume rendering picture, there exist some small tiny, discontinuous vessel parts, and I want to erase them to make the result more clearly.

 ![volume_rendering1](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/8/5/852e99f5af3d95f2207b91d9e17bd98465d845a9.jpeg)

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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:** [September 1, 2021, 3:07am UTC](https://discourse.slicer.org/t/how-volume-rendering-erase-or-hide-some-small-objects/19427/2 "2021-09-01T03:07:46Z")

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The feature is called “Mask volume”, it is available in Segment Editor. See step-by-step instructions in the [module documentation](https://slicer.readthedocs.io/en/latest/user_guide/modules/volumerendering.html#hide-certain-regions-of-the-volume) and in this video:

[![](https://img.youtube.com/vi/xZwyW6SaoM4/maxresdefault.jpg "New "Surface cut" and "Mask volume" tools for 3D Slicer segment editor") ](https://www.youtube.com/watch?v=xZwyW6SaoM4)