# How can I calculate an area on a CT image. I can calculate volumes (mm^3) but not areas (mm^2)

**URL:** <https://discourse.slicer.org/t/how-can-i-calculate-an-area-on-a-ct-image-i-can-calculate-volumes-mm-3-but-not-areas-mm-2/1549>\
**Category:** Support\
**Created:** [November 28, 2017, 9:09pm UTC](https://discourse.slicer.org/t/how-can-i-calculate-an-area-on-a-ct-image-i-can-calculate-volumes-mm-3-but-not-areas-mm-2/1549 "2017-11-28T21:09:20Z")\
**Posts on this page:** 1\
**Showing post:** 7

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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:** [August 21, 2019, 4:34pm UTC](https://discourse.slicer.org/t/how-can-i-calculate-an-area-on-a-ct-image-i-can-calculate-volumes-mm-3-but-not-areas-mm-2/1549/7 "2019-08-21T16:34:54Z")

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It computes the area of the closed curve, even if the curve points are not coplanar because they were picked from a model surface. A soap-bubble-like surface is computed for 3D curves and surface of that is reported.

To see that surface, you can use this code snippet:

```python
curve=slicer.util.getNodesByClass("vtkMRMLMarkupsClosedCurveNode")[0]
crossSectionSurface = vtk.vtkPolyData()
areaMm2 = slicer.modules.markups.logic().GetClosedCurveSurfaceArea(curve, crossSectionSurface)
crossSectionSurfaceModel = slicer.modules.models.logic().AddModel(crossSectionSurface)
crossSectionSurfaceModel.SetName("{0} surface".format(curve.GetName()))
crossSectionSurfaceModel.CreateDefaultDisplayNodes()
crossSectionSurfaceModel.GetDisplayNode().BackfaceCullingOff()
crossSectionSurfaceModel.GetDisplayNode().SetColor(curve.GetDisplayNode().GetColor())
crossSectionSurfaceModel.GetDisplayNode().SetOpacity(0.5)
crossSectionSurfaceModel.SetDescription("Area[mm2] = {0:.2f}".format(areaMm2))
print("Curve {0}: surface area = {1:.2f} mm2".format(curve.GetName(), areaMm2))

```

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