# Getting external and internal diameter of a bone

**URL:** <https://discourse.slicer.org/t/getting-external-and-internal-diameter-of-a-bone/31611>\
**Category:** Support\
**Created:** [September 7, 2023, 10:12pm UTC](https://discourse.slicer.org/t/getting-external-and-internal-diameter-of-a-bone/31611 "2023-09-07T22:12:28Z")\
**Posts on this page:** 1\
**Showing post:** 2

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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:** [September 8, 2023, 4:02am UTC](https://discourse.slicer.org/t/getting-external-and-internal-diameter-of-a-bone/31611/2 "2023-09-08T04:02:12Z")

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> [@Henry\_Lopes](#):
>
> I need 0.01mm precision

What is the resolution of your image (image spacing along each axis)?

> [@Henry\_Lopes](#):
>
> The problem is I am not being able to compute a center line which travels exactly trough the center of the internal diameter

If you segment the bone then you can use the Segment Editor module to automatically get the internal cavity and external surface of the bone using [Wrap Solidfy](https://discourse.slicer.org/t/fill-or-extract-cavities-in-segmentations-using-the-new-wrap-solidify-effect/11248/2) effect. This will allow you to get the centerline of either the internal cavity or the external surface of the bone.

> [@Henry\_Lopes](#):
>
> I’ve also tried a module supposed to compute the thickness of bones (Bone Thickness Mapping). It isn’t exactly what I need but it would be also extremely useful to know where the bone is thicker. The module simply doesn’t work

We don’t hear much from the developers of this extension, so I’m not sure if it is still maintained, but please report the issue at the [extension’s repository](https://github.com/Auditory-Biophysics-Lab/Slicer-BoneThicknessMapping) and hopefully you’ll get a response.

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