# Overlay a segmentation over a grayscale volume

**URL:** <https://discourse.slicer.org/t/overlay-a-segmentation-over-a-grayscale-volume/19314>\
**Category:** Support\
**Created:** [August 23, 2021, 12:04pm UTC](https://discourse.slicer.org/t/overlay-a-segmentation-over-a-grayscale-volume/19314 "2021-08-23T12:04:39Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![LHJ](https://avatars.discourse-cdn.com/v4/letter/l/a88e57/32.png) [@LHJ](https://discourse.slicer.org/u/LHJ)\
**Post date:** [August 23, 2021, 12:04pm UTC](https://discourse.slicer.org/t/overlay-a-segmentation-over-a-grayscale-volume/19314/1 "2021-08-23T12:04:40Z")

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I want to visualize the ground truth segmentation overlayed on the chest CT volume. Last time I managed to get a clear visible segmentation overlay (shown below).

 ![Screenshot](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/7/8/78628387813d15ed749ceb0bd91943f0fdf768fd.jpeg)

However, when I try again today, I do not get the same result. Actually, I forgot the exact procedures that I have taken last time. What I get now is

 ![Capture.PNG](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/1/1/119f4bdf1281497772dffd23e9fc5695f620046c.jpeg)

The segmentation is barely visible. Anyone has an idea how to get the first volume overlay?

Thanks a lot!

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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:** [August 23, 2021, 12:09pm UTC](https://discourse.slicer.org/t/overlay-a-segmentation-over-a-grayscale-volume/19314/2 "2021-08-23T12:09:20Z")

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You need to make the segmentation a bit larger so that the volume rendering does not occlude it. You can achieve it by lowering the threshold value or expand using margin effect. Making the volume rendering semi-transparent may help, too.