Dear SPM-ers!

I am a physics undergraduate student dabbling in fMRI analysis and i am trying to analyse the quality of some images - for specified ROIs (one background, one high intensity signal) i want to measure mean values and standard deviation.
I started my work in marsbar, but i soon found out that i need quite some information on the experiments when filling in the design, which i don't have.

Is there a more elegant way to do this than conning the program with a blank/irrelevant design?

Please, forgive me, if this question is too beginner-like, i'm just starting to learn about this software.
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Lep pozdrav
Peter Ferjančič