# Issue with surface area measurement in L3 skeletal muscle segmentation

**URL:** <https://discourse.slicer.org/t/issue-with-surface-area-measurement-in-l3-skeletal-muscle-segmentation/45916>\
**Category:** Support\
**Created:** [January 26, 2026, 10:34am UTC](https://discourse.slicer.org/t/issue-with-surface-area-measurement-in-l3-skeletal-muscle-segmentation/45916 "2026-01-26T10:34:49Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![NutritionDepartment](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/nutritiondepartment/32/81822_2.png) [@NutritionDepartment](https://discourse.slicer.org/u/NutritionDepartment)\
**Post date:** [January 26, 2026, 10:34am UTC](https://discourse.slicer.org/t/issue-with-surface-area-measurement-in-l3-skeletal-muscle-segmentation/45916/1 "2026-01-26T10:34:49Z")

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Dear 3D Slicer Development Team,

I am using 3D Slicer to segment skeletal muscle on a single axial CT slice at the L3 level for body composition research.

After segmentation, the Segment Statistics module reports a reasonable volume (~10720,7 mm³) but an unexpectedly large surface area (~20610,5 mm²), which does not reflect the true cross-sectional muscle area and seems physiologically unrealistic.  
My research goal is to measure cross-sectional muscle area at L3 (cm²) to calculate SMI and assess muscle change over time.

Could you please clarify:

1. What the “surface area” value represents in this context.

2. Whether this metric is appropriate for L3 cross-sectional muscle analysis.

3. The recommended workflow in 3D Slicer to obtain accurate muscle cross-sectional area from a single CT slice (e.g., area = volume ÷ slice thickness, or another method).

I have attached an example image and statistics output for reference.  
 ![z7465522995229_b00e115904a32426832560f1f7f6b185](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/a/1/a147c47fa311f56212b74575e325c80b8265ea1a.jpeg)

 ![z7465519967685_cd8eae851a970155a900277ef024e32c](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/2/5/256fef98ec7e48280cd1921ac74fc8f97f0f738e.jpeg)

Thank you for your support.

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<div class="post-metadata">

**Author:** ![muratmaga](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/muratmaga/32/3622_2.png) [@muratmaga](https://discourse.slicer.org/u/muratmaga)\
**Post date:** [January 26, 2026, 6:29pm UTC](https://discourse.slicer.org/t/issue-with-surface-area-measurement-in-l3-skeletal-muscle-segmentation/45916/2 "2026-01-26T18:29:18Z")

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> [@NutritionDepartment](#):
>
> Could you please clarify:

> **[Computed metrics - Segment statistics — 3D Slicer documentation](https://slicer.readthedocs.io/en/latest/user_guide/modules/segmentstatistics.html#computed-metrics)**
>
> This is a module for the calculation of statistics related to the structure of segmentations, such as volume, surface area, mean intensity, and various other metrics for each segment.

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**Author:** ![muratmaga](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/muratmaga/32/3622_2.png) [@muratmaga](https://discourse.slicer.org/u/muratmaga)\
**Post date:** [January 26, 2026, 6:31pm UTC](https://discourse.slicer.org/t/issue-with-surface-area-measurement-in-l3-skeletal-muscle-segmentation/45916/3 "2026-01-26T18:31:07Z")

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There are two different representations (labelmap and surface area) that gives SA estimate. Which one did you use?