Hi,
I can't think of an easy way of dealing with this, but I do have a
somewhat convoluted way:
- generate a binary brain mask from the phase data if possible
(this may require manual drawing but often the phase
images have some texture difference outside the brain which
might let you generate this kind of mask by spatial highpass
filtering, taking absolute values then smoothing)
- generate a binary brain mask from an anatomical (undistorted)
scan of the same individual
- register the two brain masks together
- apply the transform to the anatomical scan to get it aligned with
the phase image and then use this as the substitute magnitude
image from then on
Best of luck,
Mark
On 8 May 2009, at 13:54, Nikos Green wrote:
> Dear all,
>
> i aquired GRFM phase images but forgot for the first 3 of my
> subjects to get
> the magnitude images from the scanner (Siemens Trio). During the
> registration of my EPI data i encounter the infamous frontal
> distortion (and
> where unwarping could help me). Is there a workaround to get the
> magnitude
> image from the phase images, so that i can still use the data of my
> subjects?
>
> Thank you very much for your help,
>
> Nikos
>
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