On Fri, 17 Feb 2012 15:27:57 +0000, Anson Kairys <[log in to unmask]> wrote:
>I just finished going through the workflow for the VBM8 longitudinal analysis.
>I am wondering if these images are modulated or not (i.e. volume or concentration). If they are, can I produce un-modulated images in order to assess Gm concentration, using this very useful automated longitudinal procedure? Or would I need to use the basic approach?
There is no modulation applied to the longitudinal images, because the spatial normalization parameters (= inverse modulation) is the same for all time points of one subject. Thus, you will rather analyze absolute GM differences between the time points than relative differences. There was an discussion about the impact of modulating longitudinal data or not, but my experience is that the modulation is not necessary because it will be the same for all time points.
Christian Gaser, Ph.D.
Departments of Psychiatry and Neurology
Friedrich-Schiller-University of Jena
Jahnstrasse 3, D-07743 Jena, Germany
Tel: ++49-3641-934752 Fax: ++49-3641-934755
e-mail: [log in to unmask]
>thanks for all the great help