Dear Kenji,
if you have only two time points the results of both approaches should be identical. I usually suggest to use difference images and the simpler statistical model if additional covariates should be considered. Otherwise, you can use the SPM12 flexible factorial model. However, if you have more time points Freesurfer offers a linear mixed effects model that has some advantages:
https://surfer.nmr.mgh.harvard.edu/fswiki/LinearMixedEffectsModels
Furthermore, the sandwich estimation model by Tom Nichols is also a good alternative for more complex longitudinal designs.
http://www.nisox.org/Software/SwE/
Best,
Christian
On Tue, 27 Jul 2021 20:35:41 +0900, Kenji Yoshimura <[log in to unmask]> wrote:
>Dear CAT12/SPM12 experts,
>
>We are analyzing longitudinal surface-based analysis.
>We have 2 timepoints T1MPRAGE images (baseline and 2-year after) in each
>subject, and have run longitudinal segmentation pipeline of using CAT12.7
>(r1742).
>
>My question is on the longitudinal statistics of surface based morphometry.
>I'm not familiar with FreeSurfer, but most of previous longitudinal surface
>studies using FreeSurfer performed statistical analysis by calculating one
>value which represents degree of cortical thinning quantitatively such as
>rate (thick2-thick1 / time2-time1) or symmetrized percent change (100*rate
>/ average thick of time1 and time2) from 2 timepoints images, and using
>simple GLM (multiple group t-test). On the other hand, in SPM12/CAT12
>pipeline, we construct flexible factorial design and analyze interaction
>between group and time using both 2 timepoints images.
>
>Are there any differences, advantage and disadvantage between above 2
>analyzing methods? And is it able to create new gifti files which contain
>rate or symmetrized percent change from output files of CAT12 longitudinal
>segmentation pipeline?
>
>Thanks in advance.
>Best regards,
>
>=============================================
>Department of Neurology
>Graduate School of Medicine, Kyoto University
>Kenji Yoshimura M.D.
>54 Shogoin-Kawahara-cho
>Sakyo-ku, Kyoto, Japan
>606-8507
>TEL: 075-751-3773
>FAX: 075-753-4257
>Mail: [log in to unmask]
>=============================================
>
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