# image overlay of a cbct image and a corresponding DICOM structure 

**URL:** <https://discourse.slicer.org/t/image-overlay-of-a-cbct-image-and-a-corresponding-dicom-structure/30375>\
**Category:** Support\
**Created:** [July 3, 2023, 4:00pm UTC](https://discourse.slicer.org/t/image-overlay-of-a-cbct-image-and-a-corresponding-dicom-structure/30375 "2023-07-03T16:00:17Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![take5](https://avatars.discourse-cdn.com/v4/letter/t/6a8cbe/32.png) [@take5](https://discourse.slicer.org/u/take5)\
**Post date:** [July 3, 2023, 4:00pm UTC](https://discourse.slicer.org/t/image-overlay-of-a-cbct-image-and-a-corresponding-dicom-structure/30375/1 "2023-07-03T16:00:17Z")

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Greetings, I am new to 3D Slicer and would like to know if my thought is correct.  
I have created a cone-beam CT image by using Plastimatch fdk with a matrix size and a voxel size that are different from its corresponding DICOM CT image set. Surprizingly, 3D Slicer has shown a cooordinate-matched image overlaid result when I import the cbct.mha and add a DICOM strcture. So I guess this automatic adjustment is a functionality of the 3D Slicer. Is this correct?

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**Author:** ![pieper](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/pieper/32/8_2.png) [@pieper](https://discourse.slicer.org/u/pieper)\
**Post date:** [July 3, 2023, 5:12pm UTC](https://discourse.slicer.org/t/image-overlay-of-a-cbct-image-and-a-corresponding-dicom-structure/30375/2 "2023-07-03T17:12:29Z")

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Yes, Slicer uses the [image geometries](https://www.slicer.org/wiki/Coordinate_systems) to display the data in a patient-centric coordinate system.

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**Author:** ![take5](https://avatars.discourse-cdn.com/v4/letter/t/6a8cbe/32.png) [@take5](https://discourse.slicer.org/u/take5)\
**Post date:** [July 3, 2023, 11:32pm UTC](https://discourse.slicer.org/t/image-overlay-of-a-cbct-image-and-a-corresponding-dicom-structure/30375/3 "2023-07-03T23:32:58Z")

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Dear Steve Pieper,  
Thanks for your reply. I have read the linked image geometries page.  
Now I understand that 3D Slicer image transformation makes it possible to overlay multiple image objects having diferent matrix sizes and different voxel spacings.  
I like it a lot.