Hi Martin,
I tried this method of –addtp to add a new time point but recon-all failed with the message saying my new timepoint was not in the ‘base-tps’ file of the base template. Should I be doing something else before I run this step?
Thanks
Koushik
From: Martin Reuter [mailto:mreuter@nmr.mgh.harvard.edu]
Sent: Friday, March 14, 2014 9:31 AM
To: Govindarajan, Koushik Athreya; freesurfer@nmr.mgh.harvard.edu
Subject: 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 6th 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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--
Martin Reuter, Ph.D.
Assistant in Neuroscience - Massachusetts General Hospital
Instructor in Neurology - Harvard Medical School
MGH / HMS / MIT