In the past, “Grow from seeds” effect ignored masking settings. Now region growing can be restricted to certain areas by using “Masking” section in the Segment Editor. Masked area can be defined by image intensity range and/or existing segments.
This can be used for segmenting objects that cannot be easily separated because they have similar image intensity and they are very close to each other (or even fused together in some places). Applications include femur head and hip bone segmentation; or separating vertebrae from each other and from ribs during spine segmentation. The method can be also used for refining or splitting an already created segment.
See this short video how masking simplifies femur segmentation:
The feature is available in today’s nightly Slicer version. Any feedback or questions are welcome.