# Subtraction 2 RT Dose with Simple filters module

**URL:** <https://discourse.slicer.org/t/subtraction-2-rt-dose-with-simple-filters-module/8338>\
**Category:** Support\
**Created:** [September 8, 2019, 9:44pm UTC](https://discourse.slicer.org/t/subtraction-2-rt-dose-with-simple-filters-module/8338 "2019-09-08T21:44:10Z")\
**Posts on this page:** 2\
**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:** [September 8, 2019, 9:44pm UTC](https://discourse.slicer.org/t/subtraction-2-rt-dose-with-simple-filters-module/8338/1 "2019-09-08T21:44:10Z")

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Slicer version:4.8.1  
Hi 3D Slicer experts and all  
I have 2 RT Dose whit different Image Dimension and Image origin, which were exported from TPS. I want to subtract them with Subtract image filter in simple filters module. but the following error is displayed. How can I subtract this RT Doses?  
Thanks a lot

![subtract](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/1/f/1fc5394759d59921e4ba17cccbf6c89a5ac1711e.png)

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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:** [September 8, 2019, 10:44pm UTC](https://discourse.slicer.org/t/subtraction-2-rt-dose-with-simple-filters-module/8338/2 "2019-09-08T22:44:16Z")

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You could use the DoseAccumulation module (from the SlicerRT extension) and set the weight of the subtracted image to -1.