It is better to keep communications on the FSL list. The standard Siemens
field maps sequence is gre_field_mapping, which is a gradient echo-based
sequence. The images you sent seemed fine to me, I'm not sure why you think
they are distorted.
Peace,
Matt.
-----Original Message-----
From: Julia Foecker [mailto:[log in to unmask]]
Sent: Friday, July 08, 2011 3:18 PM
To: Matt Glasser
Subject: Re: [FSL] Unwarping with FUGUE
Siemens Trio 3T MRI;
MPRAGE sequence (TE=30, flip angle 90, Echo spacing: 0.7)...
Does this answer your question?
Julia
On Fri, 8 Jul 2011 15:06:06 -0500 Matt Glasser <[log in to unmask]> wrote
> What scanner did you acquire this on, and what sequence did you use?
>
> Peace,
>
> Matt.
>
> -----Original Message-----
> From: FSL - FMRIB's Software Library [mailto:[log in to unmask]] On Behalf
> Of Julia Foecker
> Sent: Friday, July 08, 2011 2:55 PM
> To: [log in to unmask]
> Subject: [FSL] Unwarping with FUGUE
>
> Hi,
>
> I would like to do the unwarping with FUGUE. I have the two images, a
> Fieldmap
> and the Magnitude image.
>
> FLS says: The fieldmaps required by FUGUE must be in undistorted
> coordinates.
> That is, the field map should not have any geometric distortion in it (or
> negligible amounts) as can be obtained from a spin-echo sequence, or
> gradient-echo sequences if the echo time is sufficiently small. The
> distortion
> present in a sequence can readily be seen in the absolute (or magnitude)
> image
> and normally manifests itself as a depression or extension of the inferior
> frontal lobes (when the scans are acquired axially - it is different for
> other
> acquisition planes).
>
> Actually, as seen from the magnitude image, there are geometric
distortions,
> in
> my fieldmap...however I do not know how to correct them. Is it still
> possible to
> correct them?
> And if so, how can I do this? Probably it would be easier if you can see
the
> image. Is there a possibility to send the image (in a word dok or pdf)?
>
> Thanks so much,
> Julia
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