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DICOM Segmentation dialog with tissue-density presets and Hounsfield Unit ranges
DICOM is the standard format for medical imaging — CT and MRI scans exported from hospital equipment. 3D Prep Pro accepts .dcm and .dicom files and turns them into printable 3D models by separating the scan into tissue types. Unlike a normal mesh, a DICOM scan is a stack of density measurements, not a surface. Before it can be repaired you tell 3D Prep Pro which densities to turn into solid parts — this is called segmentation.

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Segmenting your scan

When you upload a DICOM file, the DICOM Segmentation dialog opens automatically. This step is required — a scan with no segmentation can’t be repaired. Density is measured in Hounsfield Units (HU). Each segment you define becomes a separate watertight part built from everything inside its HU range.
You must complete segmentation before analysis runs. If you try to repair an unsegmented DICOM model, you’ll be prompted to re-analyze it with a segmentation preset first.

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Presets

Start from a preset, then adjust the ranges if you need to.

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Defining segments

1

Pick a preset

Choose the preset closest to what you want to print (bone, whole head, etc.).
2

Adjust the ranges

For each segment, set the Density Min and Density Max (HU). Min must be less than Max, and every segment needs a name.
3

Add or remove segments

Use Add Segment to isolate another tissue type, or remove segments you don’t need.
4

Start analysis

Click Start Analysis. Each segment is reconstructed into its own 3D part.

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Hounsfield Unit reference

Common tissue densities to help you set ranges:

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Repairing a DICOM model

DICOM repair works on the segments you created:
  • On the repair dialog you choose which segments to repair — each selected segment runs through the full repair pipeline independently, so repair time grows with the number of segments.
  • DICOM models are repaired at an optimized resolution tuned for scan data, rather than the maximum-detail setting used for regular meshes — the scan’s own slice resolution is the limiting factor anyway.
  • Surface smoothing is applied automatically so the result isn’t stair-stepped: if you leave Post-construct smoothing at 0, the engine raises it for DICOM models.
Select only the segments you plan to print. Repairing five segments takes roughly five times as long as repairing one.

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Tips

  • Bone (hard tissue) is the easiest to print — it has the clearest density boundary.
  • If a part comes out with holes or gaps, widen its HU range slightly; if it merges tissues you wanted separate, narrow it.
  • Use Slice View after repair to check the internal structure of each segment.