# How can I do a gamma analysis of the areas with a dose greater than 200 in both film images

**URL:** <https://discourse.slicer.org/t/how-can-i-do-a-gamma-analysis-of-the-areas-with-a-dose-greater-than-200-in-both-film-images/30925>\
**Category:** Support\
**Tags:** slicerrt\
**Created:** [August 2, 2023, 3:49am UTC](https://discourse.slicer.org/t/how-can-i-do-a-gamma-analysis-of-the-areas-with-a-dose-greater-than-200-in-both-film-images/30925 "2023-08-02T03:49:14Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![David\_yan](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/david_yan/32/67038_2.png) [@David\_yan](https://discourse.slicer.org/u/David_yan)\
**Post date:** [August 2, 2023, 3:49am UTC](https://discourse.slicer.org/t/how-can-i-do-a-gamma-analysis-of-the-areas-with-a-dose-greater-than-200-in-both-film-images/30925/1 "2023-08-02T03:49:14Z")

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The film is irradiated with an accelerator to obtain a dose distribution. The low-dose area is not the focus of our analysis, and the gamma analysis of the entire film will affect the judgment. How can I perform gamma analysis only on regions greater than 200 dose values?

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**Author:** ![David\_yan](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/david_yan/32/67038_2.png) [@David\_yan](https://discourse.slicer.org/u/David_yan)\
**Post date:** [August 11, 2023, 1:38pm UTC](https://discourse.slicer.org/t/how-can-i-do-a-gamma-analysis-of-the-areas-with-a-dose-greater-than-200-in-both-film-images/30925/2 "2023-08-11T13:38:46Z")

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The film is irradiated with an accelerator to obtain a dose distribution. The low-dose area is not the focus of our analysis, and the gamma analysis of the entire film will affect the judgment. How can I perform gamma analysis only on regions greater than 200 dose values?

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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:** [August 11, 2023, 1:41pm UTC](https://discourse.slicer.org/t/how-can-i-do-a-gamma-analysis-of-the-areas-with-a-dose-greater-than-200-in-both-film-images/30925/3 "2023-08-11T13:41:52Z")

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You can go to Segment Editor module, add a new segment, use Threshold effect to select region that has voxel value \> 200, then use this segmentation as input in the Dose comparison module.