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Sorry- by time points, I mean I have longitudinal data. I was pretty sure that the field map had to come from the same pt/position/scan session; like I said, it was suggested, so I threw it out there. What is the magnitude image used for in the Fieldmap toolbox? I was thinking I could substitute it with another image (acquired with same pt during same scan session) or mask. Thanks, -Julie On Wed, Aug 22, 2012 at 8:23 AM, Glad Mihai <[log in to unmask]>wrote: > Hi Julie, > > I don't quite understand what you mean with time point 1, 2, 3, etc. You > set one subject in the scanner, then started measuring the field map, after > which you measured your first trial, then you measured the field map again, > then the next trial? > > Basically every time a new person or a new position is being scanned you > will have to record a field map. Also, if you have different sequences, for > example one with a resolution of 2x2x2 mm³ and one with a resolution of > 3x3x3 mm³, you will have to record a field map corresponding to each of > those sequences, even though you scanned the same person without him or her > leaving the scanner. > > Regards, > Glad > > > On 22.08.2012 13:26, Julie McEntee wrote: > > Thanks, Glad. > > I am now acquiring the field map sequence as you describe. > > However, initially I did not have parameter set to output both mag & > phase- it was set to output phase only. > > So, I only have phase change image for the first time point. > > I do have all 3 outputs (2 mags & 1 phase) for time point 2 (& 3 in some > cased)- it was suggested that I use the mag images from time point 2 with > the phase from time point 1 (from same subject). Any input on this approach > would be appreciated. > > Thank you, > > -Julie > > sent via DROID by Verizon > On Aug 22, 2012 3:24 AM, "Glad Mihai" <[log in to unmask]> wrote: > >> Hey Julie, >> >> How many files did you get from the field mapping sequence? The Siemens >> Verio at our site gives three files using the gre_field_mapping sequence: 2 >> magnitude images (one with a short TE and one with a long TE) and a phase >> change image. They look something like this: >> >> magnitude images: >> s000*-0002-*-*-01.hdr >> s000*-0002-*-*-01.img >> s000*-0002-*-*-02.hdr >> s000*-0002-*-*-02.img >> >> phase change image: >> s000*-0003-*-*-02.hdr >> s000*-0003-*-*-02.img >> >> If you use the Fieldmap toolbox, you would only need to load one >> magnitude image (won't matter which) and the one phase change image, and >> provide it with the two TE values. >> >> I hope this helps. >> >> Glad >> >> Hello, >>> >>> I have phase-only data from a Siemens Verio gre_field_mapping sequence >>> (new to Siemens & didn't know to check that I wanted magnitude & phase >>> images). >>> >>> Is there any way I can use the Fieldmap toolbox with these phase-only >>> field maps to correct my EPI data for distortion? I have almost every other >>> image type- MPRage/T1, T2, FLAIR, SWI, DTI. >>> >>> Thank you in advance, >>> >>> -Julie >>> >>> -- >>> Julie E. McEntee, MA, CCRP >>> Image Processing Technologist >>> Center for Neuroscience & Regenerative Medicine, NIH/USUHS >>> The Henry M. Jackson Foundation for the Advancement of Military Medicine >>> >>> NIH Clinical Center >>> Building 10, Room 1C370 >>> 301-919-4273 (cell)* >>> 301-451-5175 (office) >>> [log in to unmask] >>> >> >> -- >> Glad MIHAI, M.Sc. Biomedical Physics >> Funktionelle Bildgebung >> Uni-Klinikum Greifswald >> Walther-Rathenau-Straße 46 >> 17489 Greifswald >> www.baltic-imaging-center.de >> >> > -- > Glad MIHAI, M.Sc. Biomedical Physics > Funktionelle Bildgebung > Uni-Klinikum Greifswald > Walther-Rathenau-Straße 46 > 17489 Greifswald www.baltic-imaging-center.de > > -- Julie E. McEntee, MA, CCRP Image Processing Technologist Center for Neuroscience & Regenerative Medicine, NIH/USUHS The Henry M. Jackson Foundation for the Advancement of Military Medicine NIH Clinical Center Building 10, Room 1C370 301-919-4273 (cell)* 301-451-5175 (office) [log in to unmask]