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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Michael Harms, Ph.D.
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Conte Center for the Neuroscience of Mental Disorders
Washington University School of Medicine
Department of Psychiatry, Box 8134
Renard Hospital, Room 6604 Tel: 314-747-6173
660 South Euclid Ave. Fax: 314-747-2182
St. Louis, MO 63110 Email: [log in to unmask]
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