Functionnal Connectivity between seeds

Hi,
I'm currently analysing Percentage of Signal Change within ROIs defined in MarsBar toolbox and I'd like to explore the functionnal connectivity between those ROIs thanks to REST toolbox. Unfortunalety the ROIs defined in MarsBar are not correctly defined (problem of extension? origin?). Is there a way to convert my MarsBar ROIs into ROIs well defined for seed-based connectivity in REST?

Thanks a lot for your response
Best,
Olivier GUIPPONI