Dear Wayne,
>
> A) The calculated Fieldmap and input EPI images are loaded to have
> differentorientations, despite being identical prior to input.
> Within the SPM2
> Graphics display, the calculated Fieldmap's Sagittal image has the
> Anteriorand Posterior of the brain switched. As well, is appears
> the Fieldmap has
> undergone a slight rotation whereas the EPI image has not. Are there
> settings or parameters which I have failed to set/configure properly?
I don't quite understand what is happening here. Is the output of fieldmap (i.e. the vdm*.img map) in a different orientation from the original images you put in in order to create the map? I haven't come across anything like that before. Maybe you could send me (not the mailbase) a .ps file where you show what the graphics window looks like when you display one of the images from which you calculated the vdm (voxel displacement map) and when you display the vdm-map itself.
>
> B) Related to this rotation is the matter of aligning the Fieldmap
> to the
> EPI image. The Fieldmap and EPI data set I am working with have
> differentimage resolutions (128x128x64 vs 64x64x30). In aligning
> the two images for
> fieldmap correction, is it better to work within the higher or
> lower resolution?
I would recommend you to coregister (assuming they will have different contrast) a modulus image from your phasemap data to your first EPI image, selecting the individual Re and Im images (or Modulus and phase) as "Other". Say "Coregister only", i.e. don't resample the images. That way the phase-map will be calculated in the original resolution, and then when fed into Unwarp it (the vdm-map) will be downsampled to the resolution and position of the EPI image.
Good luck Jesper
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