# maximum ring difference.

**URL:** <https://castor-project.discourse.group/t/maximum-ring-difference/116>\
**Category:** General Discussions\
**Created:** [September 25, 2019, 5:54pm UTC](https://castor-project.discourse.group/t/maximum-ring-difference/116 "2019-09-25T17:54:10Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Hadi\_Rezaei](https://avatars.discourse-cdn.com/v4/letter/h/ebca7d/32.png) [@Hadi\_Rezaei](https://castor-project.discourse.group/u/Hadi_Rezaei)\
**Post date:** [September 25, 2019, 5:54pm UTC](https://castor-project.discourse.group/t/maximum-ring-difference/116/1 "2019-09-25T17:54:10Z")

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Dear CASToR users  
I want to use CASToR to reconstruct simulated PET images and apply “maximum ring difference” for my simulation. Is there any option in ACSToR to select various maximum ring difference?? Does anyone else work on this option?

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**Author:** ![Maxime\_Toussaint](https://avatars.discourse-cdn.com/v4/letter/m/34f0e0/32.png) [@Maxime\_Toussaint](https://castor-project.discourse.group/u/Maxime_Toussaint)\
**Post date:** [September 25, 2019, 6:11pm UTC](https://castor-project.discourse.group/t/maximum-ring-difference/116/2 "2019-09-25T18:11:42Z")

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Greetings,

CASToR offer a similar feature via the ‘Maximum axial difference mm’ parameter of the geom file. However, it is not truly equivalent since axial distance is not the same as ring difference most of the time. If you absolutely need to use ring difference, I think you will need to modify the code a little.

See the CASToR general documentation for more information on that parameter! Note that you will need to modify the geom each time you “choose” an axial difference. (Or create multiple geom)

Best,  
Maxime Toussaint