when using the 2 stage model (mris_long slopes ) you do not need the qcache. In qdec you will not look at thickness, but at the percent change or the rate of thickness changes as computed by long_slopes. For that to work, you need to create/modify the .qdecrc file so that qdec finds the files in the base. Furthermore, you need to pass a “cross sectional” qdec table, with one row per subject where the fsid contains the id of the the base.

On Aug 22, 2016, at 10:24 PM, Nick Corriveau Lecavalier <nickcl8@hotmail.com> wrote:

Hi Freesurfer team,

I am planning on following this page for my longitudinal group analysis using QDEC: http://www.freesurfer.net/fswiki/FsTutorial/QdecGroupAnalysis_freeview. However, it tells me to run -qcache for all of my subjects. Since I already ran the -long stream for all my subjects, do I need to rerun them all adding the -qcache command?

Also, I have also run the long_mris_slopes on all of my subjects, which produced smoothed thickness files for all of my subjects (which are all in the ''base'' files). Does these files are okay for my QDEC analysis, or I really need to run all of my subjects all over again adding -qcache?

Thank you very much,

Nick Corriveau-Lecavalier, B.Sc. (Hons.)
Étudiant au Ph.D. recherche/intervention, option neuropsychologie clinique
Coordonateur à la recherche, Association étudiante des cycles supérieurs en psychologie de l'Université de Montréal (AÉCSPUM)
Université de Montréal
Centre de recherche de l'Institut universitaire de gériatrie de Montréal, bureau M7819
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