# 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:** 4

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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 19, 2019, 3:31am 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-2/1549/4 "2019-08-19T03:31:55Z")

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In recent Slicer Preview Releases, you can draw curves and get their surface area (2D surface, as you would expect - only one side, no thickness).

Select “Closed Curve” from the “Create and place” toolbar button:

![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/0/d/0d459c94af6ba0d0054e8f28404d91635078acf7.png)

Left-click on the image to place curve control points and right-click to finish placement:

 ![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/a/f/afbfca82fc601e6495718a98b3c4735dc5f340bd.jpeg)

Measurements on curves are still work in progress, but you can open the Python console (Ctrl-3) and copy-paste the code below to see the surface area:

```python
curves=slicer.util.getNodesByClass("vtkMRMLMarkupsClosedCurveNode")
for curve in curves:
    surfaceAreaMm2 = slicer.modules.markups.logic().GetClosedCurveSurfaceArea(curve)
    print("Curve {0}: surface area = {1:.2f} mm2".format(curve.GetName(), surfaceAreaMm2))

```

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