# ITK Simple Filters SubtractImageFilter

**URL:** <https://discourse.slicer.org/t/itk-simple-filters-subtractimagefilter/24515>\
**Category:** Support\
**Tags:** dicom\
**Created:** [July 27, 2022, 6:13am UTC](https://discourse.slicer.org/t/itk-simple-filters-subtractimagefilter/24515 "2022-07-27T06:13:58Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Will](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/will/32/16110_2.png) [@Will](https://discourse.slicer.org/u/Will)\
**Post date:** [July 27, 2022, 6:13am UTC](https://discourse.slicer.org/t/itk-simple-filters-subtractimagefilter/24515/1 "2022-07-27T06:13:59Z")

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Hello,

I am trying to replicate the effect of CT angiography by creating a subtraction from two DICOM stacks. One is a mask, which is a CT without contrast injected into the patients arteries. The other is a fill, which is the same image (ideally) but with contrast.

I think I should be able to use ITK Simple Filter’s “SubtractImageFilter” to create a subtraction from these two scans. Initially, the status in the bottom right of the parameters field says “idle.” Then, I put my scans in as inputs (I have tried both orders) and a new volume as the output. I click apply and a popup says:

Exception before execution of SubtractImageFilter  
\<class ‘slicer.util.MRMLNodeNotFoundException’\>

After this attempt, the status says “exception” for all of the ITK filters.

How can I fix this? Other than scripting, are there any free alternatives that will allow me to create subtractions?

Thanks,  
Will

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<div class="post-metadata">

**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:** [July 27, 2022, 10:02am UTC](https://discourse.slicer.org/t/itk-simple-filters-subtractimagefilter/24515/2 "2022-07-27T10:02:36Z")

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I could not reproduce this error. Could you please upload the application log (menu: Help / Report a bug) somewhere and post the link here?