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Hi Carlotta, Fieldmap unwarping is helpful but not necessary. If you have B0 scans, you'll be able to create a fieldmap with FSL <http://www.fmrib.ox.ac.uk/primers/intro_primer/ExBox19/IntroBox19.html>. The fieldmap corrections help fix any distortions you see in your functional scans. If you register your functional images to an anatomical and find that the functional image looks odd / warped / doesn't match the boundaries of the anatomical, fieldmap corrections can help correct and improve the quality of your data before you analyze it. Functional / EPI data is susceptible to distortions in the magnetic field, which causes some of the distortions to the shape of your images. That's why we collect information about the fieldmap when the data is acquired. Hope this helps answer your questions. Best wishes, Rachelle On Thu, Jun 14, 2018 at 5:48 AM, Carlotta Fabris <[log in to unmask]> wrote: > Hi Matthew, sorry to bother you again, but I was wondering if the B0 > unwarping is a necessary step in a preprocessing pipeline. > > I am asking you this, because I never did it and I don't have a field map > to put as input, but should I perform this step or is it required only in > certain conditions? > > The information I have on my data are these: Data were acquired on a 3 > Tesla Siemens Vereo MRI scanner with a 32-channel birdcage radio frequency > headcoil (neckcoil was not used, leaving 28 channels). For the functional > scans, a 28 slice axial prescription (5 mm thickness) gave whole brain > coverage. For each imaging run, a series of 190 gradient echo echoplanar > volumes were acquired over each: TE = 35 ms, TR = 2000 ms, Flip Angle =75O, > NEX = 1, BW = 100.0, FOV = 24mm, matrix =128 x 128 (in-plane resolution of > 1.875mm2). > > Thank you, > Carlotta. > > ######################################################################## > > To unsubscribe from the FSL list, click the following link: > https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=FSL&A=1 > ######################################################################## To unsubscribe from the FSL list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=FSL&A=1