Hello Experts,
I am interested in running a voxel based morphometry analysis using SPM on structural T1 MRI from mice using SPM. I should be performing 2 different analysis with different cohorts.
First; 2 groups (WT & Tg) imaged at 2 timepoints, I want to run a longitudinal analysis. After pre-Processing using SPM mouse, now I have all the grey matter segments smoothed modulated warped to the group specific template. Then I choose to apply a full factorial model with 2 factors time(T1,T2) & genotype(WT & Tg), each 2 levels and added the TIV as a covariate.
- should I consider in this model ANCOVA option from the design full factorial or not ?
- if I want to test the interaction between time and genotype, is it correct to consider the following contrast :
(Baseline _WT / Baseline_Tg / FU_WT / FU_Tg )
(-1 1 1 -1)
- Is this my input in the model is correct or should I ran the analysis on 2 steps, first the time effect for each mice then proceed for group analysis ?
Second; this is a cohort formed of 6 groups (3 time point and 2 genotypes WT & Tg ) each scanned once and I want to run a VBM to get difference between the mice at the 3 different time points and the 2 different genotypes. After pre-Processing using SPM mouse, now I have all the grey matter segments smoothed modulated warped to the group specific template. Then I choose to apply a full factorial model with 2 factors time (T1,T2, T3) & genotype(WT & Tg) and added the TIV as a covariate.
- Is my design correct ? Again should I consider the ANCOVA option?
Would it be better if I considered the genotype as a covariate instead of a main factor and check the interaction option then?
- (T1 _WT / T2_WT / T3_WT / T1 _Tg / T2_Tg / T3_Tg ) , my first contrast is T1 is more than the later time points in WT … should I set the contrast as follows
(1 -1 -1 0 0 0) or (1 -0.5 -0.5 0 0 0 )
- and for the group differences should be;
(1 1 1 -1 -1 -1)
Many Thanks,
Fatemah
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