# Creating landmarks on isosurface

**URL:** <https://discourse.slicer.org/t/creating-landmarks-on-isosurface/12497>\
**Category:** Support\
**Created:** [July 12, 2020, 9:38pm UTC](https://discourse.slicer.org/t/creating-landmarks-on-isosurface/12497 "2020-07-12T21:38:25Z")\
**Posts on this page:** 14\
**Page:** 1

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**Author:** ![ramyavij](https://avatars.discourse-cdn.com/v4/letter/r/b487fb/32.png) [@ramyavij](https://discourse.slicer.org/u/ramyavij)\
**Post date:** [July 12, 2020, 9:38pm UTC](https://discourse.slicer.org/t/creating-landmarks-on-isosurface/12497/1 "2020-07-12T21:38:26Z")

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Hi,

I am loading DICOM images from CT/MRI. I would like to create the isosurface to obtain the 3D image of the torso surface. On the torso surface, I would like to mark electrode locations.

How can I create the isosurface without segmenting any anatomy inside.

Thanks!

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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 13, 2020, 6:12pm UTC](https://discourse.slicer.org/t/creating-landmarks-on-isosurface/12497/2 "2020-07-13T18:12:15Z")

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Hi - you can turn on volume rendering, adjust the shift slider and then fiducials will be placed on the first non-transparent voxel.

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<div class="post-metadata">

**Author:** ![ramyavij](https://avatars.discourse-cdn.com/v4/letter/r/b487fb/32.png) [@ramyavij](https://discourse.slicer.org/u/ramyavij)\
**Post date:** [July 14, 2020, 3:30pm UTC](https://discourse.slicer.org/t/creating-landmarks-on-isosurface/12497/3 "2020-07-14T15:30:56Z")

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Thank you very much, Steve. That was very helpful. Can you point me to any tutorial on how to add the fiducials? I need to add more than 100 of them at a time and export their 3D coordinates.

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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 14, 2020, 3:47pm UTC](https://discourse.slicer.org/t/creating-landmarks-on-isosurface/12497/4 "2020-07-14T15:47:11Z")

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I’m not sure if there’s a tutorial specifically on placing hundreds of fiducials, but the [SlicerMorph](https://slicermorph.github.io/#two) tutorials will probably help.

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<div class="post-metadata">

**Author:** ![ramyavij](https://avatars.discourse-cdn.com/v4/letter/r/b487fb/32.png) [@ramyavij](https://discourse.slicer.org/u/ramyavij)\
**Post date:** [July 14, 2020, 4:12pm UTC](https://discourse.slicer.org/t/creating-landmarks-on-isosurface/12497/5 "2020-07-14T16:12:44Z")

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Ok, I will check them out. Thank you.

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<div class="post-metadata">

**Author:** ![ramyavij](https://avatars.discourse-cdn.com/v4/letter/r/b487fb/32.png) [@ramyavij](https://discourse.slicer.org/u/ramyavij)\
**Post date:** [July 17, 2020, 4:07pm UTC](https://discourse.slicer.org/t/creating-landmarks-on-isosurface/12497/6 "2020-07-17T16:07:01Z")

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Hi Steve, when I tried to add the markup, it doesn’t show up on any of the views. The fiducial list is grayed out. Can you please let me know how to view the added fiducials? Thanks.

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**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 17, 2020, 4:17pm UTC](https://discourse.slicer.org/t/creating-landmarks-on-isosurface/12497/7 "2020-07-17T16:17:50Z")

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See markups module documentation about how to place markups in recent Slicer Preview Releases (currently recommended version to use): [https://slicer.readthedocs.io/en/latest/user\_guide/modules/markups.html](https://slicer.readthedocs.io/en/latest/user_guide/modules/markups.html)

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<div class="post-metadata">

**Author:** ![ramyavij](https://avatars.discourse-cdn.com/v4/letter/r/b487fb/32.png) [@ramyavij](https://discourse.slicer.org/u/ramyavij)\
**Post date:** [July 17, 2020, 4:26pm UTC](https://discourse.slicer.org/t/creating-landmarks-on-isosurface/12497/8 "2020-07-17T16:26:11Z")

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Thanks. I am using 4.10. Should I down 4.11 instead?

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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 17, 2020, 4:30pm UTC](https://discourse.slicer.org/t/creating-landmarks-on-isosurface/12497/9 "2020-07-17T16:30:10Z")

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Yes, I would recommend 4.11. It has no known major limitations and contains lots of fixes and improvements compared to 4.10.

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<div class="post-metadata">

**Author:** ![ramyavij](https://avatars.discourse-cdn.com/v4/letter/r/b487fb/32.png) [@ramyavij](https://discourse.slicer.org/u/ramyavij)\
**Post date:** [July 17, 2020, 4:34pm UTC](https://discourse.slicer.org/t/creating-landmarks-on-isosurface/12497/10 "2020-07-17T16:34:14Z")

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Thank you. I will try it.

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<div class="post-metadata">

**Author:** ![ramyavij](https://avatars.discourse-cdn.com/v4/letter/r/b487fb/32.png) [@ramyavij](https://discourse.slicer.org/u/ramyavij)\
**Post date:** [July 21, 2020, 12:06am UTC](https://discourse.slicer.org/t/creating-landmarks-on-isosurface/12497/11 "2020-07-21T00:06:48Z")

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Hello,

Yes 4.11 worked well for placing fiducials. I was able to use “Persistent” feature to place multiple fiducials on the 3D volume. However, the coordinate of the fiducial changes with rotation. If I rotate the 3D volume and place the same fiducial from a different angle, the coordinates are different. How can that be prevented? Thanks!

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<div class="post-metadata">

**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 21, 2020, 12:29am UTC](https://discourse.slicer.org/t/creating-landmarks-on-isosurface/12497/12 "2020-07-21T00:29:18Z")

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Maybe you can post some screenshots to explain what you are seeing. If you place a fiducial it stays at the same 3D position when you rotate. New fiducials will be placed base on the first non-transparent data it hits.

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<div class="post-metadata">

**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 21, 2020, 12:59pm UTC](https://discourse.slicer.org/t/creating-landmarks-on-isosurface/12497/14 "2020-07-21T12:59:32Z")

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I’m still not understanding your process. Can you reproduce using a volume from the SampleData placing maybe one fiducial and describing your exact steps?

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<div class="post-metadata">

**Author:** ![ramyavij](https://avatars.discourse-cdn.com/v4/letter/r/b487fb/32.png) [@ramyavij](https://discourse.slicer.org/u/ramyavij)\
**Post date:** [July 21, 2020, 4:52pm UTC](https://discourse.slicer.org/t/creating-landmarks-on-isosurface/12497/15 "2020-07-21T16:52:28Z")

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I don’t encounter the problem anymore. Thank you for willing to help!