Hi Carlos,
To answer your last question: what you are measuring is the "actual" or "physical" magnetic field in
your field of view (well, in the parts were there is signal), no matter what your resolution is. So,
the answer is yes, you can use the 128x128 field maps to correct the distortion in the 64x64
fMRIs. You just have to be careful on how you apply the correction. I haven't used FUGUE, but I
bet you just need to align the field maps to the fMRIs (in a way so that the output of the aligned
image is also 64x64).
-Pablo
PS: Because of the smoothness of the magnetic field, it might be hard to align the FM image to the
fMRIs. Try aligning the magnitude image from any of the echoes of the FM to the fMRIs, and apply
the same matrix to the FM image.
On Fri, 16 Nov 2007 17:08:39 +0000, Carlos Faraco <[log in to unmask]> wrote:
>I am sure some of these questions have been asked before, but the more I
>read on the forum the more questions/problems/confusions arise. =]
>
> ...
>Lastly, the GRE phase maps will be acquired at 128x128, is it ok to use
>these to correct for the distortion in the fMRI 64x64s (even though there
>probably will not be much)? Reason for using 64x64, instead of 128x128, is
>to reduce slice thickness (3mm) and use the same for DTI then overlay.
>
>Thank you,
>
>Carlos
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