Creating a hemisphere mask

Hello everyone!

I’m currently studying the effects of chemoradiotherapy on healthy brain tissues in a population of brain tumours, and I am trying to segment out the healthy tissues. However, I notice that some tumour segments end up in my healthy tissues. I looked up papers online and most have created a mask to produce a single healthy hemisphere.

Would you have any advice on how I could proceed to do this? For eg does it make sense to segment the GM, WM out followed by creating a hemisphere mask and cut my GM/WM into half? But would the tumour affect registration to the MNI152 space?

Or would it be better to create the mask first, so that when registration is done in the MNI152 space, only the healthy tissue is registered within that space?

Appreciate some advice here! Thank you :slight_smile: