Hi,
I'm not sure this is something that would be beneficial, as the current method effectively normalises for this scaling in a multiplicative way, whereas removing this and adding an ICV regressor is moving to an additive model, which can give you a first-order approximation to the multiplicative normalisation, but is probably going to be less accurate generally (since I see no reason for this to be a truly additive effect).
If you really want to do it though, you could go into the script (fslvbm_3_proc) and calculate the appropriate volume change factor from the affine registration and multiply that together with the Jacobian in the modulation step.
All the best,
Mark
On 25 Mar 2013, at 14:30, Gabor Perlaki <[log in to unmask]> wrote:
> Dear all,
>
> The FSL-VBM protocol introduces a compensation (or "modulation") for the contraction/enlargement due to the non-linear component of the transformation, but not for the linear component, thus compensating for different ICVs. However, it would be more appropriate for me, if the protocol compensates also for the linear and non-linear components of the registration, and I use ICV as a regressor.
>
> Is it possible somehow, with FSL-VBM?
>
> Thanks,
> Gabor
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