I’m building some regions-of-interest by combining regions defined in some atlas. For example, I want to build a region called ‘hippocampus’, but I need to combine a lot of smaller regions defined by my atlas (e.g. CA1, dentate gyrus, etc.). Each region in the atlas is defined with a particular number.
To do this, I’ve been using fslmaths to threshold by a specific value and binarising in order to get the individual sub-regions I want, and then adding all those sub-regions together to build the mask with all of the combined values. Is there a better (faster, and requiring fewer images to be generated) way?