Two approaches for wall thickness quantification are available in Dragonfly (since version 4.0) : volume thickness map and thickness mesh. This post will briefly illustrate both.

The following demo uses a CT dataset of walnut ( Data courtesy of European Institute for Molecular Imaging (EIMI), Muenster, Germany 

First demo is for volume thickness map. We segment the walnut shell as ROI1, then right-click on it and find the menu “Create Volume Thickness Map”:
This will create a new grayscale image/dataset, of which each voxel has an intensity indicating the local wall thickness at the location of that voxel. All voxels outside the ROI1 have zero thickness measurement.   
Again, the volume thickness map uses the gray level to indicate the local thickness. You can use the Probe tool to find the measurement at a specific location. 
Second demo is for thickness mesh.  Using the same ROI1 we created previously, we can find a tool called “To a Thickness Mesh” in the Export toolset of Segment tab (Remember you have to select the ROI in the top-right list as the current object to see the thickness mesh tool enabled):
This will produce a new mesh object in the top-right list. This mesh provides the wall thickness measurement at every surface vertex, and the thickness is coded by color as well (in this example, the mesh has 750,560 vertices). The Scalar Information toolset allows users for exporting the measurements to a CSV file (therefore, the exported CSV file in this example will have 750,560 rows, each indicating the thickness at one vertex).
You can also view the thickness mesh in 3D, where the surface colormap are consistent with the 2D views for thickness measurement.