# Dose comparison module

**URL:** <https://discourse.slicer.org/t/dose-comparison-module/35665>\
**Category:** Support\
**Created:** [April 23, 2024, 4:36am UTC](https://discourse.slicer.org/t/dose-comparison-module/35665 "2024-04-23T04:36:58Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![azam](https://avatars.discourse-cdn.com/v4/letter/a/ea666f/32.png) [@azam](https://discourse.slicer.org/u/azam)\
**Post date:** [April 23, 2024, 4:36am UTC](https://discourse.slicer.org/t/dose-comparison-module/35665/1 "2024-04-23T04:36:58Z")

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Hi every one  
slicer version: 5.2.2  
I have 2 RT Dos exported from the treatment planning system. I want to compare these 2 dose distributions using the Dose Comparison module in 3 D slicer. my CT slice thickness is 5mm. but I want to calculate gamma index with 3%/3mm.  
Can 3D Slicer do this calculations accurately or should the CT Slice thickness be less than 5 mm?  
can you help me?  
thanks a lot

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<div class="post-metadata">

**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:** [April 29, 2024, 11:43am UTC](https://discourse.slicer.org/t/dose-comparison-module/35665/2 "2024-04-29T11:43:57Z")

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I apologize that right now I have time only for a very quick answer, but maybe this will help you make progress.

I just checked and in SlicerRT itself there is no resampling done on the input volumes. Looking at Plastimatch (the library that does the actual comparison), I can give you two hints:

1. Read the paper based on which the algorithm was implemented, see [src/util/gamma\_dose\_comparison.h · master · plastimatch / plastimatch · GitLab](https://gitlab.com/plastimatch/plastimatch/-/blob/master/src/util/gamma_dose_comparison.h#L22)
2. There are indications in the code for some resampling to be performed, see [src/util/gamma\_dose\_comparison.cxx · master · plastimatch / plastimatch · GitLab](https://gitlab.com/plastimatch/plastimatch/-/blob/master/src/util/gamma_dose_comparison.cxx#L274)  
Please dig a bit more to see when exactly and how (if you have some programming knowledge or willingness to read some code)

Good luck!