Hi Gang (and other gurus),

I have two studies whose subject pools overlap significantly and I'm trying to run a VBM analysis using both sets of data. I want to be able to take into account a number of complications:

• Our scanner was replaced between the two studies. I have no idea what the effect of this improvement is on the GM probabilities estimated by SPM.
• The second study was carried out much more quickly than the first, so there's a significant spread in the times between the two scans for each subject that was scanned for both studies. This is important because grey matter volume is strongly inversely related to age.
• The subjects fall into three groups; healthy controls and two patient populations, one of which is not present in the second study.

It looks to me like I can simply feed 3dLME the data I have, making sure it has subject IDs, ages at scan, group assignments, and perhaps an indicator of which scanner was used, plus whatever variables I'm interested in, but I'm curious whether there might be any pitfalls with this approach. (For instance, does the non-randomly distributed missing data pose a problem?)

Thanks,
ijs