# Spatial information in 2D segmentations

**URL:** <https://discourse.slicer.org/t/spatial-information-in-2d-segmentations/46642>\
**Category:** Support\
**Created:** [April 2, 2026, 6:40pm UTC](https://discourse.slicer.org/t/spatial-information-in-2d-segmentations/46642 "2026-04-02T18:40:43Z")\
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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:** [April 3, 2026, 12:32pm UTC](https://discourse.slicer.org/t/spatial-information-in-2d-segmentations/46642/3 "2026-04-03T12:32:41Z")

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Segment Statistics module computes area and volume of each segment. Area is computed in 3D, which means both sides of a flat single-slice segments are included. You can divide the reported surface value by 2 to get the cross-sectional area, i.e., the area that you see on a single image.

There are also several modules for computing area. I generated this summary using ChatGPT, but I confirm that it is accurate (I reviewed it and fixed minor inaccuracies):

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### 📌 1. **Segment Cross‑Section Area** (in **Sandbox** extension)

- This module computes cross‑sectional area of a segmentation **along an image axis** (e.g., axial, sagittal, coronal or any IJK axis you choose).
- You can install it by opening the **Extensions Manager** in Slicer and installing the **Sandbox** extension.

👉 Best when you want area per slice along standard image axes.

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### 📌 2. **SegmentGeometry** (in **SlicerBiomech** extension)

- This extension can compute **cross‑sectional area** (plus other shape metrics) **along an arbitrary direction or line** , not just the image axes.
- It’s useful if you want cross‑sections in non‑orthogonal directions or aligned with a specific anatomical axis.
- It outputs area and additional geometric properties like perimeter, Feret diameter, moments of inertia, etc.

👉 Best when you need cross‑section metrics oriented in a custom way.

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### 📌 3. **VMTK modules** (in **SlicerVMTK** extension)

- The **Vascular Modeling Toolkit (VMTK)** extension includes modules like _Cross‑section analysis_ or _Stenosis measurement_.
- These can compute cross‑sections **along a centerline or curved path** , often used for vessels or tubular structures.

👉 Best for vascular work or when the structure follows a path rather than straight sections.

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### 📌 3. **Markups module**

- If you need the area of a structure in a **single 2D slice** , you can draw a closed curve markup and enable **area measurement** in the Markups module’s **Measurements** section.

👉 Best for measuring area of a simple shape in a single 2D slice.

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