Dear FSLers,
I want to conduct a longitudinal analysis with diffusion images using randomise.
My sample has 150 subjects with 2 groups (G) on 2 sites (S), who underwent 2 mri exams at approximatively 2 years.
I want to study the interaction group*age on changes between time 1 and time 2. I ran TBSS on each subject’s image.
Can I use a design matrix with 2 images per subject or a design matrix with a difference image (timepoint 2 – timepoint 1) as explained in fslwiki? Are they both of them valid?
Model longitudinal:
G1S1
G2S1
G1S2
G2S2
Subject1
Age_time1
0
0
0
Subject1
Age_time2
0
0
0
Subject2
0
Age_time1
0
0
Subject2
0
Age_time2
0
0
Subject3
0
0
Age_time1
0
Subject3
0
0
Age_time2
0
Subject4
0
0
0
Age_time1
Subject4
0
0
0
Age_time2
Model substract:
G1S1
G2S1
G1S2
G2S2
age_time1
Subject1
Age_time2-Age_time1
0
0
0
Age_time1
Subject2
0
Age_time2-Age_time1
0
0
Age_time1
Subject3
0
0
Age_time2-Age_time1
0
Age_time1
Subject4
0
0
0
Age_time2-Age_time1
Age_time1