I compared 2 groups and found a cluster with difference in cortical volume. I want to have a mean value of cortical volume, thickness, and surface area for each subject for this cluster, that I can use for further statistical analysis. What do you recommend?

I'm not looking for a value that would only be the one from the peak vertex (I've tried it with mri_segstats already). I'm rather looking for a volume, thickness and surface area value from EACH vertex from the cluster, so that I can have a mean value for each metric if I average them with a basic statistical tool.