Is there a way to determine the area a segment takes up in a given slice? I’m interested in generating a plot from a CT scan, anterior to posterior, of the area taken up by a segment slice-by-slice (if that makes sense).

If you were to do this on a sphere, for example, you’d wind up with a gaussian. (I think, I’d have to double-check the math on that…)

There’s nothing built-in to do that, but it would be possible with a little python scripting. Are you interested in trying that? We could give some pointers.

This should do what you need (this script puts results in a table but you can easily create a plot from the vtkDoubleArray):

segmentationNode = getNode('Segmentation')
segmentId = 'Segment_1'
# Get segment as a numpy array
import vtk.util.numpy_support
import numpy as np
vimage = segmentationNode.GetBinaryLabelmapRepresentation(segmentId)
narray = vtk.util.numpy_support.vtk_to_numpy(vimage.GetPointData().GetScalars())
vshape = vimage.GetDimensions()
# Reshape the segment volume to have an array of slices
narrayBySlice = narray.reshape([-1,vshape[1]*vshape[2]])
# Count number of >0 voxels for each slice
narrayBySlicePositive = narrayBySlice[:]>0
areaBySliceInVoxels = np.count_nonzero(narrayBySlicePositive, axis=1)
# Convert number of voxels to area in mm2
areaOfPixelMm2 = vimage.GetSpacing()[0] * vimage.GetSpacing()[1]
areaBySliceInMm2 = areaBySliceInVoxels * areaOfPixelMm2
# Save results to a new table node
tableNode=slicer.mrmlScene.AddNewNodeByClass("vtkMRMLTableNode", "Segment quantification")
updateTableFromArray(tableNode, areaBySliceInMm2)
tableNode.GetTable().GetColumn(0).SetName("Segment Area")