Skip to main content

Region Grow

The Region Grow tool performs region growing on the active mask to split the segmentation into separate objects based on connectivity. Starting from a user-specified seed point within the mask, it identifies and extracts all connected voxels as a new segment. This is useful for isolating individual structures from a combined segmentation.

Accessing the Tool​

  1. Navigate to the Segmentation tab in the ribbon.
  2. Click Region Grow in the Create Mask section.

Parameters​

Connectivity​

OptionDescription
6-connectivityOnly the neighboring faces of the selected voxel are considered (default).
26-connectivityThe neighboring faces, nodes, and vertices of the selected voxel are considered.

Options​

  • Multiple layer: If checked, the operation will be applied to all slices of the dataset. If unchecked, it will only be applied to the current slice (default: checked).
  • Keep original mask: If checked, preserves the original mask while creating a new segment.

Result​

  • Target mask: Select the mask object where the segmentation result will be stored.
  • Replace: Replace the selected mask with the segmentation calculated by this operation (default).
  • Merge: Merge the segmentation calculated by this operation into the selected mask object. n active mask that contains multiple disconnected or separable regions.
  1. Open the Region Grow tool from the Segmentation tab.
  2. Choose the appropriate Connectivity setting (6-connectivity or 26-connectivity).
  3. Enable/disable Multiple layer option as needed.
  4. Enable Keep original mask if you want to preserve the original.
  5. Select the Target mask where results will be stored.
  6. Choose Replace or Merge mode.
  7. Left-click on the desired region in either the 2D or 3D view to place the seed point.
    • Use Ctrl+drag in the 3D view to rotate while selecting.
    • Press P key for quick selection mode.
  8. The connected region is automatically extracted based on the selected connectivity mode.
  9. Repeat for additional regions as need
  10. Choose the appropriate Connectivity setting.
  11. Click on the desired region in a slice view to place the seed point.
  12. The connected region is automatically extracted and displayed.

How It Works​

Region growing operates on binary mask data:

  1. The algorithm starts at the seed point.
  2. It examines neighboring voxels based on the connectivity setting.
  3. If a neighbor is part of the mask (non-zero), it is added to the region.
  4. The process repeats until no more connected voxels are found.
  5. The result is a new mask containing only the connected region.
info

This tool operates on existing mask data, not directly on grayscale volume intensities. For intensity-based region growing, use the Dynamic Region Grow tool.

Use Cases​

  • Isolating Objects: Extract a single bone from a skeleton segmentation.
  • Separating Organs: Isolate individual organs from a combined tissue mask.
  • Component Analysis: Identify and separate disconnected regions within a mask.

Tips​

  • Use 6-connectivity for more conservative separation (only face-adjacent voxels are connected).
  • Use 26-connectivity for more inclusive separation (face, edge, and corner-adjacent voxels are connected).
  • Enable Multiple layer to process all slices simultaneously.
  • Enable Keep original mask when experimenting to preserve your original segmentation.
  • Use P key as a shortcut for quick point selection mode.
  • Combine with the Split Mask tool to automatically separate all disconnected regions.

See Also​