Flood filling and fast marching for Head and Neck tumours


I was trying to use fast marching to segment Head and Neck tumours. But I don’t think I’m getting a satisfactory result. Below is an image of the segmentation done using fast marching. What could be the issue?

While I used the flood filling method, if the set intensity tolerance is 2 or 3 and if doesn’t give me the needed result, can I adjust the intensity tolerance level and neighbourhood size? I tried that but it doesn’t seem to affect the image. It seems like I must know the intensity tolerance and neighbourhood size before clicking on the image. Is there a way to readjust those parameters to generate the intended result?

Are these semi-automatic methods suitable for segmenting head and neck tumours? Is there any other semi-automatic segmentation method other than watershed, grow from seeds(though both seemed identical to me), threshold and just enough interaction methods which will work fine on head and neck tumours?

Slicer version: 4.13.0-2022-01-27
Many thanks in advance