# How can I make a plane from 3 midsagittal fiducials?

**URL:** <https://discourse.slicer.org/t/how-can-i-make-a-plane-from-3-midsagittal-fiducials/15981>\
**Category:** Support\
**Tags:** segmentation\
**Created:** [February 13, 2021, 8:56pm UTC](https://discourse.slicer.org/t/how-can-i-make-a-plane-from-3-midsagittal-fiducials/15981 "2021-02-13T20:56:57Z")\
**Posts on this page:** 6\
**Page:** 1

<div class="post-metadata">

**Author:** ![ebryson](https://avatars.discourse-cdn.com/v4/letter/e/f05b48/32.png) [@ebryson](https://discourse.slicer.org/u/ebryson)\
**Post date:** [February 13, 2021, 8:56pm UTC](https://discourse.slicer.org/t/how-can-i-make-a-plane-from-3-midsagittal-fiducials/15981/1 "2021-02-13T20:56:57Z")

</div>

Hi,

I’m trying to place fiducials and open curves on a juvenile skull’s fontanelle (the unfused place where there’s no bone), so it’s landmarking an open/negative space not on the actual model. To do that I want to create a mid-sagittal slice that’s based on 3 fiducials that I make along the midline of the skull.

So I’m wondering: How do I make a slice/cut-plane based on my own fiducials?

Does anyone know how to do that?  
Thanks!

---

<div class="post-metadata">

**Author:** ![muratmaga](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/muratmaga/32/3622_2.png) [@muratmaga](https://discourse.slicer.org/u/muratmaga)\
**Post date:** [February 13, 2021, 9:04pm UTC](https://discourse.slicer.org/t/how-can-i-make-a-plane-from-3-midsagittal-fiducials/15981/2 "2021-02-13T21:04:34Z")

</div>

Create a blank MarkupsPlane node and copy and paste those three points from the MarkupFiducial into the Plane one (right click on the Control Points table)

 ![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/7/a/7a4e4a7e6a2b3cc5fe35f5ca4efe6a7debacb281.png)

---

<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:** [February 13, 2021, 9:09pm UTC](https://discourse.slicer.org/t/how-can-i-make-a-plane-from-3-midsagittal-fiducials/15981/3 "2021-02-13T21:09:25Z")

</div>

You might also find ACPC Transform module useful, which can reorient an image to make the midsagittal plane exactly aligned with the sagittal view.

Short demo/tutorial video:

> [@ACPC Transform for MRI scans- Slicer 4.11](https://discourse.slicer.org/t/acpc-transform-for-mri-scans-slicer-4-11/15762/5):
>
> I did a quick recording of how ACPC alignment works in latest Slicer Preview Release: [[acpcdemo] ](https://www.youtube.com/watch?v=sdrRv3JrgTU) It would be great if you could create a nice description/tutorial of how to use it (with a few screenshots). Slicer documentation is now in markdown format, which is the format that this forum uses, so you can write this as a new post in this topic and I will move it to the Slicer documentation when it is ready.

Documentation:

[https://www.slicer.org/wiki/Documentation/Nightly/Modules/ACPCTransform](https://www.slicer.org/wiki/Documentation/Nightly/Modules/ACPCTransform)

---

<div class="post-metadata">

**Author:** ![ebryson](https://avatars.discourse-cdn.com/v4/letter/e/f05b48/32.png) [@ebryson](https://discourse.slicer.org/u/ebryson)\
**Post date:** [February 15, 2021, 2:29am UTC](https://discourse.slicer.org/t/how-can-i-make-a-plane-from-3-midsagittal-fiducials/15981/4 "2021-02-15T02:29:37Z")

</div>

Thank you so much for the quick reply, I’m checking with my supervisor to see if this is what she had in mind but it looked good when I tried it out.

Another quick question, on my adult skulls I resample my open-curves landmarks to the model surface so they’re evenly spaced. Since I’m moving points into the open space over the fontanelle to measure that curve I can’t resample (because they want to jump to the bone surface). Because they won’t be evenly spaced will that mess up my final comparison between adults and juveniles?

Thank you!

---

<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:** [February 15, 2021, 3:03am UTC](https://discourse.slicer.org/t/how-can-i-make-a-plane-from-3-midsagittal-fiducials/15981/5 "2021-02-15T03:03:51Z")

</div>

You can resample without snapping to surface.

If you compare curves (not control point positions) then it might not matter if control points are spaced equally.

I don’t know if it helps you, but in recent Slicer Preview Release you can choose not to snap points to visible surface when you are moving control points in a 3D view (initial placement is still done on the surface, but you can simply skip the fontanelle and then later insert points along the curve using Ctrl + Left-click).

---

<div class="post-metadata">

**Author:** ![ebryson](https://avatars.discourse-cdn.com/v4/letter/e/f05b48/32.png) [@ebryson](https://discourse.slicer.org/u/ebryson)\
**Post date:** [February 15, 2021, 2:51pm UTC](https://discourse.slicer.org/t/how-can-i-make-a-plane-from-3-midsagittal-fiducials/15981/6 "2021-02-15T14:51:49Z")

</div>

I forgot you could do that, thank you!

And I didn’t know about the shortcut for adding points that’s going to be really helpful.