I have one scan for the patient before treatment that I want to compare to one scan I have for the patient after treatment with ROIs, is there a way to do this? I have tried under the second level covariates putting them each into their own group but when I get to the 2nd level results it shows no significance. I don't know if it is because I am unable to compare only 2 scans that way or if there is another way to do it?