Hi Anna

I am not a statistician, but I would not control for duration separately, but rather use the time variable for that. 

It does not need to be in years (can be days out months).

Measures closer in time are more correlated than measures further apart. Lme makes use of that information through the time variable.

Best Martin

Best Martin

Sent via my smartphone, please excuse brevity.

-------- Original message --------
From: Anna Jonsson

Date:06/24/2014 11:52 AM (GMT+01:00)
To: Martin Reuter
Cc: Freesurfer support list
Subject: Re: [Freesurfer] free-surfer longitudinal Qdec table

thank you. and one other question; rather than putting years as the time variable, can i do time 1 (for baseline) and 2 (for follow-up), and jsut control for time between scans instead?

On Fri, Jun 13, 2014 at 5:42 PM, Martin Reuter <mreuter@nmr.mgh.harvard.edu> wrote:

Hi Anna, whenever it says qdec-long the table is in qdec format (with a fsid-base as second column. It would then use the longitudinally processed results, which is what you want , both for lme and 2 stage model.

Best Martin

Sent via my smartphone, please excuse brevity.

-------- Original message --------
From: Anna Jonsson

Date:06/09/2014 3:47 PM (GMT+01:00)
To: Freesurfer support list

Subject: Re: [Freesurfer] free-surfer longitudinal Qdec table

Hi, sorry for more questions, but i have a few. When running the first step of the lme implemented tools, doing the command mris_preproc --qdec-long qdec.table.dat --target study_average --hemi lh --meas thickness --out lh.thickness.mgh (assembles your thickness data into a single lh.thickness.mgh file), am I correct that this just needs to be a "normal" cross-sectional qdec table that free surfer subsequently makes into long format by --qdec-long option? so the lnogitudinal qdec table is only used in the two stage modell? This too just uses the cross-sectionally derived scans?  Im confused where the .long runs become used?

thank you and kind wishes

On Wed, Jun 4, 2014 at 5:01 PM, Martin Reuter <mreuter@nmr.mgh.harvard.edu> wrote:

Hi Anna,

Fsid is the cross sectionall name without the .long.

Best martin

Sent via my smartphone, please excuse brevity.

-------- Original message --------
From: Anna Jonsson
Date:06/04/2014 7:22 AM (GMT-05:00)
To: Freesurfer support list
Subject: [Freesurfer] free-surfer longitudinal Qdec table

Hi,

I would like to make my freesurfer longitudinal qdec table for the to use in the lme matlab tools. However, does the fsid need to refer to the longitidunally derived subject; eg XXX.long, or the cross-sectionally derived subject, eg XXX. Im not sure based on the specification online.

 Kind Regards

Anna

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