I'm not sure I follow. If I understand, you are finding sig diff in PCG
volume when you extract it the volume value for each subject (scaled by
etiv) and process in SPSS. The part I don't understand is what you are
doing with QDEC. I don't think QDEC can be used to test ROI volume.
On 05/09/2017 05:58 PM, John Anderson wrote:
> Dear Dr Doug,
> I have two groups of subjects (80 patients and 40 controls). I
> analyzed the data using Freesurfer v6.0.
> I want to study the difference between the groups in "precentral gyrus
> volume". After "recon-all" I built Qdec table and I used Qdec to
> compute the comparison by including eTIV a covariate. After correcting
> the results using Monte Carlo simulation or adjusting for FDR I found
> no difference between the groups in volume neither in surface area.
>
> I adjusted the precentral gyrus volume values for eTIV using the commands:
>
> mri_label_volume -eTIV $SUBJECTS_DIR/${i}/mri/transforms/talairach.xfm
> 1948 $SUBJECTS_DIR/${i}/mri/wmparc.mgz 2017
> mri_label_volume -eTIV $SUBJECTS_DIR/${i}/mri/transforms/talairach.xfm
> 1948 $SUBJECTS_DIR/${i}/mri/wmparc.mgz 2024
>
> I extracted the adjusted volume values to SPSS then I ran box plots
> comparison between the groups and I found difference at (P<0.0001)
> Why Qdec doesn't show the difference between the groups although the p
> value is very small. What I am doing wrong in Qdec? Is it wrong to
> include eTIV a covariate?
>
> Thank you for any advice
> John
>
>
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--
Douglas N. Greve, Ph.D.
MGH-NMR Center
gr...@nmr.mgh.harvard.edu
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