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Dear FSL-experts, I am interested in a longitudinal design for a retrospective VBM study, however I am failing to set it up by myself and especially confused, if it is at all possible, what I am trying to achieve: We are investigating a progressive neurological disorder showing clearly bilateral grey matter volume differences (increases and decreases) compared to controls. We would now like to take advantage of the several scan time points, that we have of each patient, to find out, how the disease progression is expressed by means of grey matter volume. Basically we want to know, which structures within the patient brain show a grey matter volume decrease (as well as increase) with disease progression. As this is a retrospective clinical study, our patients were measured at differing frequencies and time-intervals. While we can adjust for the differing time-intervals, I am unsure how to deal with the unequal amount of scans. Is this procedure at all possible using randomise or PALM? And if yes, would you have a suggestion on how to set up such a design? Thanks a lot already in advance, any help on this regard is greatly appreciated! Best wishes, Bastian