# Getting HU values from one ROI applied to two different images

**URL:** <https://discourse.slicer.org/t/getting-hu-values-from-one-roi-applied-to-two-different-images/11307>\
**Category:** Support\
**Tags:** segmentation\
**Created:** [April 26, 2020, 5:21pm UTC](https://discourse.slicer.org/t/getting-hu-values-from-one-roi-applied-to-two-different-images/11307 "2020-04-26T17:21:51Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![gmadevs](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/gmadevs/32/6702_2.png) [@gmadevs](https://discourse.slicer.org/u/gmadevs)\
**Post date:** [April 26, 2020, 5:21pm UTC](https://discourse.slicer.org/t/getting-hu-values-from-one-roi-applied-to-two-different-images/11307/1 "2020-04-26T17:21:52Z")

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Hi all, is there a way to extract ROI values as arrays by using the same ROI on different images?  
Suppose I want to register two CT scan in two different timepoints, I’d like to draw a ROI and then having the HU values as array with coordinates of image 1 and image 2. I read about the command `slicer.util.` `arrayFromVolume` but I’m not sure it’s the same case as mine.

Thank you!

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**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:** [April 28, 2020, 1:58pm UTC](https://discourse.slicer.org/t/getting-hu-values-from-one-roi-applied-to-two-different-images/11307/2 "2020-04-28T13:58:07Z")

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Be sure to resample the data to the same pixel space (e.g. using the Resample Image (BRAINS) module) before doing array-level access to the pixel data.