# Threshold and hounsfield unit inclusion
**URL:** https://discourse.slicer.org/t/threshold-and-hounsfield-unit-inclusion/14044
**Category:** Support
**Created:** [October 14, 2020, 10:51pm UTC](https://discourse.slicer.org/t/threshold-and-hounsfield-unit-inclusion/14044 "2020-10-14T22:51:35Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@S\_Jo](https://discourse.slicer.org/u/S_Jo)
#### Post date: [October 14, 2020, 10:51pm UTC](https://discourse.slicer.org/t/threshold-and-hounsfield-unit-inclusion/14044/1 "2020-10-14T22:51:35Z")
Operating system: Windows 10
Slicer version: 4.1.1.
Hello,
I am using threshold method to measure ROI. A question came up if the threshold is set at -30, is -30 included or does the inclusion of values start from -29?
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### Author:  [@lassoan](https://discourse.slicer.org/u/lassoan)
#### Post date: [October 14, 2020, 11:26pm UTC](https://discourse.slicer.org/t/threshold-and-hounsfield-unit-inclusion/14044/2 "2020-10-14T23:26:59Z")
The threshold range is inclusive on both sides.
Note that 1 HU is such a small difference that it should not matter either way. For example, magnitude of image noise typically tens of HU.
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### Author:  [@S\_Jo](https://discourse.slicer.org/u/S_Jo)
#### Post date: [October 19, 2020, 1:24am UTC](https://discourse.slicer.org/t/threshold-and-hounsfield-unit-inclusion/14044/3 "2020-10-19T01:24:31Z")
Thank you for the information. Knowing the noise level is very helpful.