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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:
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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

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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