Hello fellow SPM'ers,
I've got a few basic questions regarding acquisition settings for B0
fieldmaps that I hope you could indulge me in answering.
First: I've yet to see any concrete recommendations as to optimal
settings for B0 maps. I'm currently gathering field maps using a
factory optimized sequence which leaves me with a phase and magnitude
image that the Fieldmap toolbox accepts readily. However, the specific
parameters of the field map, such as voxel size, and slice number is
seldom in correspondence with the functional data I collect. Am I right
in assuming that this is suboptimal, and that we SHOULD acquire field
maps that are in exact correspondence to the functional images with
regard to 1: voxel size 2: number of slices and 3: acquisition
orientation. Am I forgetting something?
Second: Suppose I have a rather large amount of data with fieldmaps
for in which voxel size and number of slices is not in correspondence
with the functional data. Is it still possible to perform fieldmap based
unwarping?
Third: Suppose I run multiple experiments during one scanning session,
in which the acquisition parameters(no. of slices, voxel size, slice
gap, TR, TE) vary between experiment. Is it necessary to acquire a
fieldmap matched to each experiment?
I have a sneaking suspicion that the reason why I can't find these
questions answered anywhere is because the answers are rather obvious to
those well-versed in these matters, but I hope you will find time to
answer me in spite of this.
Best wishes,
Haakon,
University of Oslo
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