Hi,
The order of the steps was as you wrote.
Highpass filtering should give you an image that
highlights the areas of noise in the background
(as these are very "rough" and full of high-frequency
content). The hope is then that smoothing (after
taking the abs) generates something where the
average value in the background is higher than
inside the brain and you could threshold it.
However, this is far from guaranteed to work, so
it might just be that it won't work at all. I've never
tried it - it was just an idea.
All the best,
Mark
On 11 May 2009, at 14:49, Nikos Green wrote:
> Thanks very much Mark,
>
> i will try that. Just one quick question concering the first step:
> In what order do the proposed steps apply. I tried spatial highpass
> filtering, abs. values and smoothing but i do not get an image from
> which I
> can make a mask easily. Am i missing sth.?
>
> Thanks,
> Nikos
>
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