Issue with surface area measurement in L3 skeletal muscle segmentation

Support
1

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

z7465519967685_cd8eae851a970155a900277ef024e32c
z7465519967685_cd8eae851a970155a900277ef024e32c911×696 41.9 KB

Thank you for your support.

2
3

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