Dear Paul,
It is difficult to be sure from just looking at the image and the intensity range, but I would guess that this is in rad/s rather than Hz, based on the intensities. However, they might not be in either units and might need some scaling.
In terms of checking how well they correct the distortions, I would make sure that you check both phase encode directions (e.g. positive and negative options). If both look bad, then it probably needs scaling, but that what that would be depends on what the results look like. However, you could try multiplying by (2*pi) in case it was in Hz, but I find that unlikely. I think it is either in rad/s or has some other scaling.
If you are still stuck after this, then email is and include some images (jpegs or equivalent) of what you are seeing after the unwarping (upload the images to a photo sharing website and just include the link in the email).
All the best,
Mark
On 3 Feb 2014, at 18:30, Paul Geha <[log in to unmask]> wrote:
> Dear all,
>
> I am trying to do a fieldmap correction for data available online part of the f_1000 effort (http://fcon_1000.projects.nitrc.org/indi/pro/nki.html).
> the data comes with a fieldmap image and a field magnitude image. However, I am not sure whether the fieldmap is the final image in radian/seconds that I can use in FEAT or whether I should process it further in Fsl_prepare_fieldmap. The image is attached.
>
> Can somebody please take a look and let me know (if possible from the image) if I need to anything further? The problem is that I am using the image and getting a more distorted filtered_func_data not an improved one.
>
> Thanks a lot!
> Paul
>
> <fieldmapBOLD_brain.nii.gz>
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