# How to analyze the thickness of the model

**URL:** <https://discourse.slicer.org/t/how-to-analyze-the-thickness-of-the-model/2735>\
**Category:** Support\
**Created:** [April 30, 2018, 1:56pm UTC](https://discourse.slicer.org/t/how-to-analyze-the-thickness-of-the-model/2735 "2018-04-30T13:56:06Z")\
**Posts on this page:** 1\
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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:** [May 1, 2018, 4:04pm UTC](https://discourse.slicer.org/t/how-to-analyze-the-thickness-of-the-model/2735/2 "2018-05-01T16:04:55Z")

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“Thickness” is not a very well defined term for models (surface meshes), but for shell-like meshes it is probably not too difficult to estimate it robustly and accurately.

Potential approaches:

A. Extract medial surface and estimate thickness as 2x of distance from medial surface. There are various ways of computing these in Slicer. One possible workflow:

- Compute medial surface using **Simple Filters module - BinaryThinningImageFilter**.
- Compute distance map using **Simple Filters module - DanielssonDistanceMapImageFilter**. Input is binary: Yes; Use image spacing: Yes.
- Copy distance values from the distance map to model node using **Probe volume with model** module.

Critical part is the medial surface extraction. If you find that it is not accurate enough then you may to use smaller voxel sizes for the model-\>labelmap conversion, or use a different medial surface extraction method (for example, medial surface extractor in VMTK or [PowerCrust algorithm](https://github.com/timhutton/vtkpowercrust)).

 ![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/2/3/2352e218fd3bb74629d3c8fd3d10969880c1f06e.png)

B. Implement a custom algorithm in C++. Something like this should be very easy to implement if you are already familiar with C++ programming using VTK: [http://mmmanual.com/thickness/](http://mmmanual.com/thickness/).

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