# Dose Volume Histogram Comparison

**URL:** <https://discourse.slicer.org/t/dose-volume-histogram-comparison/3543>\
**Category:** Support\
**Created:** [July 20, 2018, 6:44pm UTC](https://discourse.slicer.org/t/dose-volume-histogram-comparison/3543 "2018-07-20T18:44:56Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![aseman](https://avatars.discourse-cdn.com/v4/letter/a/c0e974/32.png) [@aseman](https://discourse.slicer.org/u/aseman)\
**Post date:** [July 20, 2018, 6:44pm UTC](https://discourse.slicer.org/t/dose-volume-histogram-comparison/3543/1 "2018-07-20T18:44:56Z")

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Hi 3D slicer experts:  
I want to compare two DVH curves in one diagram .I created DVHs with Dose Volume Histogram module , then I used the DVH Comparison module , but it doesn’t show the second DVH for me. how I can see them simultaneously in one diagrame?  
thanks

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**Author:** ![cpinter](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/cpinter/32/7995_2.png) [@cpinter](https://discourse.slicer.org/u/cpinter)\
**Post date:** [July 20, 2018, 7:12pm UTC](https://discourse.slicer.org/t/dose-volume-histogram-comparison/3543/2 "2018-07-20T19:12:19Z")

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Dose Comparison only gives you quantitative comparison results. If you want to see DVHs in the same graph, then you need to do it in the Dose Volume Histogram module. Just calculate one set of DVHs (DoseVolume1 with StructureSet), then the second set (DoseVolume2 with StructureSet), and click the Show all button. All DVHs should show up, the ones belonging to DoseVolume2 with dashed lines to be able to differentiate.

Hope this helps!

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**Author:** ![PaoloZaffino](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/paolozaffino/32/81052_2.png) [@PaoloZaffino](https://discourse.slicer.org/u/PaoloZaffino)\
**Post date:** [February 20, 2019, 9:44pm UTC](https://discourse.slicer.org/t/dose-volume-histogram-comparison/3543/3 "2019-02-20T21:44:26Z")

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@cpinter, can I ask how the DVHs are compared?  
What is that percentage I get?

Thank you!  
Paolo

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**Author:** ![cpinter](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/cpinter/32/7995_2.png) [@cpinter](https://discourse.slicer.org/u/cpinter)\
**Post date:** [February 20, 2019, 11:04pm UTC](https://discourse.slicer.org/t/dose-volume-histogram-comparison/3543/4 "2019-02-20T23:04:23Z")

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The percentage is the pass rate of the 1D gamma comparison algorithm, which is the same as the gamma you use to compare dosimetry measurements on films (2D) or gels (3D).

There is a detailed description in the documentation of the function, see [https://github.com/SlicerRt/SlicerRT/blob/master/DoseVolumeHistogram/Logic/vtkSlicerDoseVolumeHistogramComparisonLogic.h#L48-L55](https://github.com/SlicerRt/SlicerRT/blob/master/DoseVolumeHistogram/Logic/vtkSlicerDoseVolumeHistogramComparisonLogic.h#L48-L55)  
It references a paper (Ebert et al. 2010) that you can read if you want more details.