I'm gonna have to do some searching -- somewhere on the web there are pics of MRI's of people who have MS, and some easy-to-understand explanations. I had the web site noted at one time..but can't seem to find it now.
Anyway..I really have very limited knowledge or experience with MRI's. But I think that the periventricular areas are in the "white matter". The lesions that show up "with contrast" are supposedly the more active, more recent ones. I've never had an MRI "with contrast", so can't compare.
I don't try to interpret MRI's, anyway. I certainly don't have the medical background or training to begin to look at them and know what I'm seeing! I just have learned that each radiologist and each neuro seem to look at them a bit differently, describe what they're seeing a bit differently, and sometimes don't see the same things at all. Which is why when people switch doctors, the new doc will often ask for MRI's, even if the patient has recently had them done, because docs get used to working with specific labs and specific radiologists, and they'll know what the other means when they say things like "....periventricular areas in the white matter" :)
...I am not a doctor, nor health professional, and don't pretend to be one, here.....