# Threshold in the segment editor

**URL:** <https://discourse.slicer.org/t/threshold-in-the-segment-editor/29316>\
**Category:** Support\
**Tags:** threshold\
**Created:** [May 6, 2023, 2:23pm UTC](https://discourse.slicer.org/t/threshold-in-the-segment-editor/29316 "2023-05-06T14:23:28Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![duan](https://avatars.discourse-cdn.com/v4/letter/d/a9adbd/32.png) [@duan](https://discourse.slicer.org/u/duan)\
**Post date:** [May 6, 2023, 2:23pm UTC](https://discourse.slicer.org/t/threshold-in-the-segment-editor/29316/1 "2023-05-06T14:23:28Z")

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What is the threshold in the segment editor? Does this threshold represent the window width of the corresponding CT value of human tissue?

 ![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/8/6/86b1028a1623eb2ba7fd6c2d1b00c443b1fb3fa2.jpeg)

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<div class="post-metadata">

**Author:** ![pieper](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/pieper/32/8_2.png) [@pieper](https://discourse.slicer.org/u/pieper)\
**Post date:** [May 6, 2023, 2:40pm UTC](https://discourse.slicer.org/t/threshold-in-the-segment-editor/29316/2 "2023-05-06T14:40:14Z")

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The threshold is in terms of the data values in your images. If the data is a clinical CT, then it would be [HU](https://radiopaedia.org/articles/hounsfield-unit). But your data appears to be a scan of a printed film, so the units are probably not calibrated.