# Cannot apply Threshold on ROI

**URL:** https://discourse.slicer.org/t/cannot-apply-threshold-on-roi/7269
**Category:** Support
**Tags:** segmentation, threshold
**Created:** [June 20, 2019, 9:57pm UTC](https://discourse.slicer.org/t/cannot-apply-threshold-on-roi/7269 "2019-06-20T21:57:18Z")
**Posts on this page:** 1
**Showing post:** 2

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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: [June 20, 2019, 10:04pm UTC](https://discourse.slicer.org/t/cannot-apply-threshold-on-roi/7269/2 "2019-06-20T22:04:45Z")

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Preview is shown on the entire image visible in the view. When you apply the threshold, it is applied to the region specified in the segmentation node’s geometry.

Segmentation node’s geometry is defined by default by the first selected master node. If you switch master nodes, maximum extent of the segmentation will not change. You need to click on “Specify geometry” button to change the extent of the segmentation.

![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/f/6/f6d726ba2dc21621909757eb5448d8a4b909e595.png)

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