Dear Carles,
see below for my answers...
On Wed, 27 Sep 2006 13:00:44 +0200, CARLES M. FALCON FALCON <[log in to unmask]> wrote:
>Dear Chrsitian, Lynne, Ged and the rest of the SPM community,
>
>Thanks for your answer.
>
>My sample aged from 12 to 17 years. There were two gropus, a control group and
>a nervous anorexia patient group. The pre-post scan delay was about one year.
>The control group was taken to evaluate the growth effects in VBM, in order to
>remove those effects from the patient group analysis. I have still two
>questions concerning how things have to be done to get the best results:
>
>- Is modulating normalized images necessary to distinguish volume variations
>due to growth from those due to the treatment applied to the patients? I think,
>in this case, jacobians should be applied although this being a longitudinal
>study.
I still think that you don't have to modulate your images, because you are looking for relative
differences between the time points. The warps for each time point are the same for one subject
and you would modulate the images with the same jacobians.
>- Is an ANOVA (two groups, two conditions, proportional scaling?) the best way
>to distinguish which differences are related to growth from those related to
>treatment?
No, you need a longitudinal design. For one group you can use Anova within subjects and for
more than one group you can use the PET model multi-group conditions & covariates. I have also
prepared the longitudinal statictic in the vbm2 toolbox and tried to simplify the interactions for
VBM purposes.
Best regards,
Christian
>
>Thanks again for your time and for your advise,
>
>Yours
>
>Carles
>
>
>
|