Hi,

with one group you want to check if atrophy is significantly different from zero? That is probably the case for any group (e.g. aging), so it won't tell you anything really. Also, if you don't find atrophy in a region it doesn't mean it's not there (only your group size is too small to detect it).
So the only real use I can think of, would be a test-retest study, where the assumption is that there is no change?

Sadly Qdec cannot do 'one sample group mean', otherwise you could do that in qdec. If only you had a second 'control' group, then it could be done. You can use long_mris_slopes to compute rate or percent change maps (one for each subjects) and then you can use qdec to analyze those rate maps across groups.
If you don't have a control group, you could still use long_mris_slopes (it can also map and stack the rate maps on fsaverage) and then simply run the one sample group mean in mri_glmfit.

some info is also here:
https://surfer.nmr.mgh.harvard.edu/fswiki/FsTutorial/LongitudinalTutorial_freeview
and
https://surfer.nmr.mgh.harvard.edu/fswiki/LongitudinalTwoStageModel

Best, Martin

On 01/30/2014 09:18 AM, amirhossein manzouri wrote:

Hi,

Would you please advise if it is possible to do longitudinal statistical analysis within a group with two time points in Qdec. And if it is not possible in Qdec how I suppose to do it?

Best regards,
Amirhossein Manzouri
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Martin Reuter, Ph.D.
Assistant in Neuroscience - Massachusetts General Hospital
Instructor in Neurology   - Harvard Medical School
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