Hi Yolanda,
actually it is advantageous if the template is build from more time points. You don't need to process the images again, just do your statistical analysis with the time points you are interested in.
But: why restrict the statistics to a subset of the data? If you are interested in yearly change, you can compute that from all time points. If you are interested in seeing if the atrophy rate increases over time, use a piecewise linear model (node at 6 months) and see if the slopes increase, etc. Removing time points from the statistics is usually a bad idea as you loose power.
Best, Martin
On 03/18/2013 01:15 PM, Yolanda Vives wrote:
Dear FreeSurfer experts,
I have run a longitudinal study considering multiple time points (7 scans/subject on average) with FS 5.1. However, I am interested in the percent changes between two time points only (between 0 and 6 months and between 0 and 1 year). Should I run the longitudinal stream from step 2 (template) two more times (1.- considering only 0 and 6 months scans and 2.- considering only 0 and 12 months scans) or is it correct even if my templates were built with all the time scans together?
Thank you for your help, Yolanda _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer