# Drawing Circle on CT Image

**URL:** <https://discourse.slicer.org/t/drawing-circle-on-ct-image/20387>\
**Category:** Support\
**Created:** [October 27, 2021, 2:12pm UTC](https://discourse.slicer.org/t/drawing-circle-on-ct-image/20387 "2021-10-27T14:12:01Z")\
**Posts on this page:** 1\
**Showing post:** 3

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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:** [October 28, 2021, 12:55pm UTC](https://discourse.slicer.org/t/drawing-circle-on-ct-image/20387/3 "2021-10-28T12:55:33Z")

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> [@pieper](#):
>
> Instead you could use a 3D fiducial (point with radius) to fit the 3D shape of the bone.

You can also use 2 points of a markups fiducial node to specify a circle by copy-pasting a few lines of code to into the Python console as shown in [this example](https://slicer.readthedocs.io/en/latest/developer_guide/script_repository.html#define-edit-a-circular-region-of-interest-in-a-slice-viewer).

I’ve created a modified script that allows you to place 2 circles by specifying 6 points on the circumference: [Compute bone axis in 3D Slicer by specifying two circles. · GitHub](https://gist.github.com/lassoan/99514fb5edf98e1e3dda926253dc9742)

You can use this by placing one fiducial list containing 6 points then copy-pasting into the Python console:

[![](https://img.youtube.com/vi/1DG3y1TqWvw/maxresdefault.jpg "Custom interactive measurement using Python scripting") ](https://www.youtube.com/watch?v=1DG3y1TqWvw)

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