# Watershed and grow from seeds

**URL:** <https://discourse.slicer.org/t/watershed-and-grow-from-seeds/25240>\
**Category:** Support\
**Tags:** segmentation\
**Created:** [September 13, 2022, 3:44pm UTC](https://discourse.slicer.org/t/watershed-and-grow-from-seeds/25240 "2022-09-13T15:44:54Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![MPhilip](https://avatars.discourse-cdn.com/v4/letter/m/5f8ce5/32.png) [@MPhilip](https://discourse.slicer.org/u/MPhilip)\
**Post date:** [September 13, 2022, 3:44pm UTC](https://discourse.slicer.org/t/watershed-and-grow-from-seeds/25240/1 "2022-09-13T15:44:54Z")

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Hi,

I was trying to use watershed and grow from seeds segmentation methods on PET images. But the process of implementing the semi-automatic methods in a 3D slicer seems identical- i.e. labelling(seeds) the tumour and the background as two different segments using paint and applying the watershed or grow from seeds method. I would like to know how exactly these two segmentation methods differ.

I could see that grow from seeds uses a modified grow cut algorithm, which automatically segments the tumour from the background provided the seeds on the PET image. I would like to know what is done in the watershed method similarly. I used the tumour and background labelled using paint for grow from seeds and also for watershed methods. is that right? I could read that the watershed method applies a smoothing effect to the segmented tumour whereas it is not applied for grow from seeds and the watershed is comparatively slower than grow from seeds.

I would also like to know how the concept of rainwater falling on terrain is implemented in the watershed method available in the 3D slicer. I am quite confused between these two methods.

Hope you would help.

Many thanks.