Re: [Freesurfer] adding time points to longitudinal base template

Hi Koushik,

there is a way to add time points without recreating the base: recon-all -long <tpNsubjid> <longbasesubjid> -addtp -all

This is what the recon-all help says about that: "If a new timepoint needs to be added to a longitudinal run where a base subject has already been created (from prior timepoints), then the -addtp command can be added to the -long command in order to 'fix-up' the longitudinal stream to accept the new timepoint. Note that the base subject is *not* recomputed using the new timepoint. This potentially introduces a bias, and it is recommended to NOT add a time point this way! Instead recreate the base from all time points and run all longitudinals again."

So it's up to you. But given you already have 5 time points in your base and add only 1, you may be fine. The base should be pretty stable with 5 and if the 6th is not too different, it should not matter much. I don't think anyone has ever done a thorough analysis about adding time points.

Best, Martin

On 03/11/2014 10:08 AM, Govindarajan, Koushik Athreya wrote:

Dear FS experts,

       I have a serial study in which I have run cross-sectional 

and longitudinal analysis on 5 time points. Now, I want to add a 6^th time point to my dataset. Do I have to rerun my base template creation step from scratch or is there a way to just add further time points to an existing template?

Thanks

Koushik

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