Hi,
This looks reasonable to me.
Most of the values are between -1000 and +1000 rad/s, and given that shimming at 7T is very difficult, these sorts of changes are well within the typical range. Only a few very extreme voxels are near +/- 4000.
All the best,
Mark
On 2 Jun 2014, at 22:42, P. Chang <[log in to unmask]> wrote:
> Hello,
>
> We're trying to use field map to unwrap our EPI image. We've used 'fsl_prepare_fieldmap' to convert the unit of field map to rad/s. The output image ranges about -4000 to + 4000. This range seems quite big for us but we're unsure what it supposed to be. What is typical range of the field map in rad/s at 7T? Is there anyway to tell if the field map is converted correctly or not?
>
> I attached the field map for your reference. The command we've used: fsl_prepare_fieldmap SIEMENS FmapPhase.nii.gz FmapMag_brain.nii.gz FmapRads 1.01
>
> And it shows:
> Loading volumes
> Phase loaded
> Magnitude loaded
> Mask loaded
> Rewrapping phase range to [-pi,pi]
> Number of phase splits = 8
> Calculating starting matrices (860 by 860)
> Finished connection_matrices
> 2490 constraints left
> Did while loop 859 times
> Done. Created FmapRads for use with FEAT.
>
>
> Thank you,
>
> Pei
> <FmapRads.nii.gz>
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