My apologies for re-posting this one more time, but I'm really stumped.
I would REALLY appreciate it (and would be happy to treat you to a
beverage of your choice at the next OHBM) if someone that has
successfully acquired and applied field map correction from a Philips
Achieva could contact me with what they had to do.
I'd be happy to then summarize whatever I learn to the broader FSL-list.
thanks,
-MH
On Fri, 2012-06-29 at 11:38 -0500, Michael Harms wrote:
> Hello FEAT users with Philips scanners,
>
> I would be highly appreciative if someone that has successfully applied
> fieldmapping correction (B0 unwarping) using Philips scanner data would
> contact me off the list so that I could pick your brain.
>
> We have data from a multi-site study, of which one site was a Philips
> scanner. I *thought* that I knew what needed to be done to apply
> fieldmapping correction for the data from this site, but the comparison
> in the Prestats report of "undistorted example_func to undistorted
> fieldmap" clearly shows that we don't have something right.
>
> The odd thing is that the "Unwarping shift map" from the Philips site
> data shows a spatial pattern that is completely different from what we
> observe from 4 different Siemens sites. Namely, it has a rather strong
> S/I gradient, with negative voxel shifts inferiorly, and positive voxel
> shifts superiorly. This makes me wonder if what we collected wasn't a
> proper fieldmap (the site collected a FFE with "B0 field map = yes" and
> "delta TE = 2.5 ms"), but if that's the case, I'd like to know what the
> site needs to do differently at the time of acquisition.
>
> Thanks in advance!
> -MH
>
>
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