# Questions about Slicer Coordinates

**URL:** <https://discourse.vtk.org/t/questions-about-slicer-coordinates/11485>\
**Category:** Development\
**Tags:** file-formats\
**Created:** [May 18, 2023, 9:31am UTC](https://discourse.vtk.org/t/questions-about-slicer-coordinates/11485 "2023-05-18T09:31:25Z")\
**Posts on this page:** 7\
**Page:** 1

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**Author:** ![marlon.ma](https://discourse.vtk.org/user_avatar/discourse.vtk.org/marlon.ma/32/6091_2.png) [@marlon.ma](https://discourse.vtk.org/u/marlon.ma)\
**Post date:** [May 18, 2023, 9:31am UTC](https://discourse.vtk.org/t/questions-about-slicer-coordinates/11485/1 "2023-05-18T09:31:25Z")

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![image](https://discourse.vtk.org/uploads/default/original/2X/1/18c81e83a5c5e676209948e8399d34602635e336.png)  
This is the image information I read and printed from DCM images through ITK

Based on the calculation, I found that the physical spatial coordinates should be at (-420, -140, -420, -140, -140，140)

 ![image](https://discourse.vtk.org/uploads/default/original/2X/e/ebf54436f131ef785ee7699048cd03063e32f54e.png)  
Why is the coordinate information displayed in the 3D slicer not like this

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**Author:** ![lassoan](https://discourse.vtk.org/user_avatar/discourse.vtk.org/lassoan/32/50_2.png) [@lassoan](https://discourse.vtk.org/u/lassoan)\
**Post date:** [May 20, 2023, 4:33am UTC](https://discourse.vtk.org/t/questions-about-slicer-coordinates/11485/2 "2023-05-20T04:33:19Z")

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According to the ITK reader, the physical LPS coordinates are in the range:

- L [-420, -140] = R 140 to R 420
- P [-420, -140] = A 140 to A 420
- S [-140, 140] = I 140 to S 140

In Slicer, the G view’s offset (A 297) is in the same range as in ITK, but the yellow view is not (L 285.5). Most likely you have not loaded the image using [DICOM module](https://slicer.readthedocs.io/en/latest/user_guide/data_loading_and_saving.html#dicom-data).

If you find the physical coordinates range are still different in ITK and Slicer then please share the image (upload somewhere and post the link here) and I’ll have a look.

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**Author:** ![marlon.ma](https://discourse.vtk.org/user_avatar/discourse.vtk.org/marlon.ma/32/6091_2.png) [@marlon.ma](https://discourse.vtk.org/u/marlon.ma)\
**Post date:** [May 20, 2023, 2:13pm UTC](https://discourse.vtk.org/t/questions-about-slicer-coordinates/11485/3 "2023-05-20T14:13:15Z")

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I am sure I used the dicom module to read the image

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<div class="post-metadata">

**Author:** ![marlon.ma](https://discourse.vtk.org/user_avatar/discourse.vtk.org/marlon.ma/32/6091_2.png) [@marlon.ma](https://discourse.vtk.org/u/marlon.ma)\
**Post date:** [May 20, 2023, 2:27pm UTC](https://discourse.vtk.org/t/questions-about-slicer-coordinates/11485/4 "2023-05-20T14:27:35Z")

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image is delete

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**Author:** ![lassoan](https://discourse.vtk.org/user_avatar/discourse.vtk.org/lassoan/32/50_2.png) [@lassoan](https://discourse.vtk.org/u/lassoan)\
**Post date:** [May 20, 2023, 4:12pm UTC](https://discourse.vtk.org/t/questions-about-slicer-coordinates/11485/5 "2023-05-20T16:12:24Z")

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WIth both the latest Slicer Stable Release (Slicer-5.2.2) and a recent Slicer Preview Release (Slicer-5.3.0-2023-04-25) the yellow slide range is negative L, which means R, which is correct.

 ![image](https://discourse.vtk.org/uploads/default/original/2X/6/67267cffd7b589dee26857cfa73aa82598e2e1ff.png)

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<div class="post-metadata">

**Author:** ![marlon.ma](https://discourse.vtk.org/user_avatar/discourse.vtk.org/marlon.ma/32/6091_2.png) [@marlon.ma](https://discourse.vtk.org/u/marlon.ma)\
**Post date:** [May 21, 2023, 1:45am UTC](https://discourse.vtk.org/t/questions-about-slicer-coordinates/11485/6 "2023-05-21T01:45:13Z")

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green why not negative ?

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<div class="post-metadata">

**Author:** ![lassoan](https://discourse.vtk.org/user_avatar/discourse.vtk.org/lassoan/32/50_2.png) [@lassoan](https://discourse.vtk.org/u/lassoan)\
**Post date:** [May 21, 2023, 3:22am UTC](https://discourse.vtk.org/t/questions-about-slicer-coordinates/11485/7 "2023-05-21T03:22:53Z")

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The direction code (L, R, A, P, I, S) is chosen so that when you move the slider to the right the numerical value increases.