External Email - Use Caution
Hello,
I have been looking through tutorials on the website and referencing the
freesurfer mail archives, but I am a bit unsure if I am following the
correct procedures for my analysis. The main source of confusion on my end
stems from trying to apply tutorials (and in some cases the tutorials they
reference) to my longitudinal data. I appreciate your help in advance.
I have longitudinal data with scans from two time points. My variables were
all collected at time point 1 (TP1). I am interested in change in cortical
thickness in relation to these variables as well as interacting effects on
cortical thickness; some of these variables are continuous (e.g. suvr) and
some are categorical (e.g. alleles). My initial goal was to use QDEC, but I
quickly learned that should use glmfit. For the purpose of understanding, I
am writing in focusing on age and suvr as my variables. I started with the
longitudinal tutorial.
1.) The first point of confusion came near the end of the tutorial at
"long_stats_slopes". The command runs for me, but I'd appreciate a second
look on whether this is correct:
long_stats_slopes --qdec $SUBJECTS_DIR/long.qdec.table.dat --stats
lh.aparc.stats --meas thickness --sd $SUBJECTS_DIR --do-avg --do-rate
--do-pc1 --do-spc --do-stack --time years --stack-avg [desired
path]/stack-avg --stack-rate [desired path]/stack-rate --stack-pc1 [desired
path]/stack-pc1 --stack-spc [desired path]/stack-spc
>From there, the tutorial says to run my data through the glm tutorial. I
have several points of confusion here - the first being that I'm concerned
that I may not have my data set up correctly.
2.) I looked at the FSGD examples and built my file from them, and I also
referenced the mail archives for similar projects to mine. I am unsure as
to whether I should be using the [LONG] files created or the [BASE] files
created with the longitudinal tutorial in my FSGD file. For example, if I
am just looking at age and another factor (suvr) should my FSGD look like
this...
GroupDescriptorFile 1
MeasurementName thickness
Class subject
Variables age suvr
Input Subject1_TP1 subject 57 0.93
Input Subject1_TP2 subject 57 0.93
Input Subject2_TP1 subject 64 1.22
Input Subject2_TP2 subject 57 1.22
Or should it point to the directories made during the [BASE] step of the
longitudinal tutorial like this?
GroupDescriptorFile 1
MeasurementName thickness
Class subject
Variables age suvr
Input Subject1_base subject 57 0.93
Input Subject2_base subject 56 1.06
3.) From there, I understand that I need an individual contrast matrix for
each contrast that I'd like to run. Here is what I have been using:
Age: 0 1 0
Suvr: 0 0 1
Age x Suvr: 0 1 -1
4.) Next, I ran through the rest of the GLM tutorial to assemble the data
and run glmfit, followed by a clusterwise comparison for multiple
comparisons
mris_preproc --fsgd file_name.fsgd \
--target fsaverage \
--hemi lh \
--meas thickness \
--out lh.file_name.thickness.00.mgh
mri_surf2surf --hemi lh \
--s fsaverage \
--sval lh.file_name.thickness.00.mgh \
--fwhm 10 \
--cortex \
--tval lh.file_name.thickness.10.mgh
mri_glmfit \
--y lh.file_name.10.mgh \
--fsgd file_name.fsgd dods\
--C age.mtx \
--C suvr.mtx \
--C age_suvr.mtx \
--surf fsaverage lh \
--cortex \
--glmdir lh.directory_name.glmdir
mri_glmfit-sim \
--glmdir lh.gender_age.glmdir \
--cache 4 neg \
--cwp 0.05\
--2spaces
5.) My last question is, if I want to run glmfit to analyze my data with
other variables, is there anything that I have to delete or re-run on my
end? From what I understand, I would only have to run glmfit and its'
corrections again.
I appreciate your help - I just want to make sure that I am, and that I am
following these tutorials properly.
Vince