Here is the tutorial for longitudinal processing -  https://surfer.nmr.mgh.harvard.edu/fswiki/LongitudinalProcessing

The 'base' and 'long' steps of the longitudinal processing should be re-run after adding new timepoints.

Yujing

From: freesurfer-bounces@nmr.mgh.harvard.edu <freesurfer-bounces@nmr.mgh.harvard.edu> On Behalf Of Eszter Boros
Sent: Wednesday, January 15, 2025 1:52 PM
To: Freesurfer support list <freesurfer@nmr.mgh.harvard.edu>
Subject: [Freesurfer] longitudinal analyses, more than 2 timepoints

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Dear FreeSurfer Team,

We are analyzing some longitudinal data (baseline [0], 6 months, 1 year, 1.5 years) using FreeSurfer 7.4.1.
We already analyzed two timepoints (basline[0] and 6 months) but now we are trying to look at 4 timepoints in total.

I was wondering what the best way would be to do this. For the longitudinal processing, should we create 3 bases/within-subject templates between 0-6 months (this is already done), 0-1year, 0-1.5years), or between 0-6months, 6months-1year, 1year-1.5years. Or both?

Also, is it okay to correct/edit only the bases?

After the longitudinal processing, can we create a Longitudinal Table and apply the two-stage model (LongitudinalTwoStageModel) method? Or because of the 4 time points, we need to apply something else.

Thank you for your help in advance!

All the best, Eszter