On Thursday 15 May 2008 16:09:42 David Lythgoe wrote:
> > I was just informed that GE DOES NOT add any filtering to the DTI data,
> > it just zero pads. So in this case, I am assuming it is safe to use
> > ApplyXFM4D.
>
> Hi Carlos,
>
> I'm not sure about that. GE typically apply a fermi filter (look it up on
> the web if you don't know the details) to kspace data before the FFT. For
> the DTI sequence the Fermi radius is set to half the x-matrix size. I
> believe the width is set to the default value of 10, regardless of matrix
> size.
>
I tend to agree with Dave. I don't run DTI on GE, but I would expect to get
ringing artefacts in the zero-padded image without a k-space filter, due to
sharp edge between zeroes and high-frequency parts of the k-space.
Martin
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