Hi,
this has been answered before - check the archives for it.
Cheers,
Andreas
Am 12.09.15 00:09 schrieb "FSL - FMRIB's Software Library on behalf of
SUBSCRIBE FSL Haiqing Huang" unter <[log in to unmask] on behalf of
[log in to unmask]>:
>Hi, FSL experts,
>
>We recently compared two groups (patients vs. normal controls) T1
>structure difference following FSL-VBM user guide. Our patients' head
>sizes measured by TICV (total intracranial volume) are significantly
>larger than our controls'. And we do find papers report their FSL-VBM
>results with and without controlling for TICV.
>
>We found following statement about TIV in this paper (Good et.al. 2002,
>"Automatic differentiation of anatomical patterns in the human brain:
>validation with studies of degenerative dementias."):
>"Since we have incorporated this correction for volume change induced by
>spatial normalization, it is appropriate to include TIV as a confounding
>covariate to remove any variance due to differences in head size. Without
>the modulation step, spatial normalization removes differences in head
>size and thus TIV does not need to be included as a confounding
>covariate."
>
>Our question are:
>1. In current FSL-VBM analysis, is head size removed? If yes, at which
>step and how? Normalization or modulation?
>2. Even if head size is controlled by FSL-VBM, is it still necessary to
>list head size as covariate, since the two groups' head sizes are
>significantly different?
>
>Thank you very much. Any thoughts on this will be very helpful to us.
>
>
>Haiqing Huang
>
>Biomedical Engineering Department
>University of Florida
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