Dear FreeSurfer experts,
We have a longitudinal study design with up to 5 time points. However, we
both want to do a baseline cross-sectional analysis and later a
longitudinal analysis. All subjects have been run through the longitudinal
pipeline (only the base was edited). We want to start analysing baseline
cross-sectionally using QDEC. I have read through the wiki guides but would
like to make sure that we are doing it correctly. We have done/plan to do
the following:
1. The [CROSS], edited [BASE] and [LONG] is processed.
2. We will create a qdec table called qdec.table.dat. However, because we
want to use the improved longitudinal runs [LONG] (i.e., because the [BASE]
has been edited] the first column in the QDEC table (i.e., fsid) has been
changed to include the longitudinal names (please see below). In addition,
we have included the line *SUBJECTS_DIR /my/path/to/subject/data* to let
FreeSurfer know that it is the longitudinal directories that should be used
(is this the correct why to let FreeSurfer know that it is the
"longitudinal runs" which should be used?).
SUBJECTS_DIR /my/path/to/subject/data
fsid Gender Group Age
d115a.long.d115_base 1 1 19
d120a.long.d120_base 0 1 22
...
2. We transfer the default fsaverage to the subject directory.
3. To presmooth the data onto the target we run the following command:
*recon-all
-long <tpid> <baseid> -qcache*
When the above steps are done we plan to load it into QDEC.
Is the above steps correct for doing a cross-sectional group analysis in
QDEC?
Best regards,
Kasper Jessen
MD, PhD student