The vacuum or cone head effect of normalization (I don't think that's
an official name).
We have seen this too and it seems to occur when there is signal
inhomogeneity in the T1. It may not be obvious from the display but I
would bet that the signal values from the top of the brain are much
lower than in the center of the brain. Bias correction does not seem
to fix the problem for us (or we have done it wrong). Repositioning
the brain at the origin occasionally helps, but only sometimes. The
only ways I have found to fix this are
1) skull stripping the brain and normalizing to a skull stripped
template. That can require a lot of work.
2) normalizing the functional data instead.
I'd also be interested if others have found an easier way to deal with this.
darren
On Thu, Nov 6, 2008 at 9:34 AM, Michelle Welman
<[log in to unmask]> wrote:
> Dear,
>
> As you can see in my attachment the normalisation goes completely wrong,
> does anybody kow what I did wrong and how I should do it correctly?
>
> Kind regards,
>
> Michelle Welman
>
> ________________________________
> Waarom chatten Robbie en Adriana? Check 't
> hier...
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Darren Gitelman
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