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Dear Michael, > I am having trouble figuring out how to use the --field option in eddy, and whether I can even use it with my DWI data. the --field option is much less convenient than the --topup option, and we always recommend for future acquisitions that people acquire blip-up-blip-down data instead of “traditional” fieldmaps. For existing data with “traditional” fieldmaps you need to register that fieldmap to the first volume in the diffusion data set. As part of that registration the fieldmap will be resampled to the same matrix and resolution as the diffusion data. You can do that with FLIRT. It is not an easy registration problem though since the contrasts and distortions can be quite different between the two. Also, are you sure that the header values for the diffusion data are correct? That is some very high resolution diffusion data. Jesper > > Whenever I try to apply the field command with my data, I get an error that says: > "Loading prediction makerImage Exception : #3 :: Attempted to add images/ROIs of different sizes > libc++abi.dylib: terminating with uncaught exception of type RBD_COMMON::BaseException > Abort trap: 6" > > I believe this is because the dimensions on my field map and DWI data are different. For my field map, running fslinfo gives the following information: > data_type INT16 > dim1 140 > dim2 180 > dim3 9 > dim4 1 > datatype 4 > pixdim1 1.500000 > pixdim2 1.500000 > pixdim3 16.000000 > pixdim4 9.000000 > cal_max 0.0000 > cal_min 0.0000 > file_type NIFTI-1+ > > This field map is a nifty file created by 9 DICOM field maps obtained axially, and are the only images that were taken of the field in data collection. > > However, my DWI data has the following information: > data_type FLOAT32 > dim1 400 > dim2 512 > dim3 180 > dim4 61 > datatype 16 > pixdim1 0.500000 > pixdim2 0.500000 > pixdim3 1.000000 > pixdim4 1.000000 > cal_max 0.0000 > cal_min 0.0000 > file_type NIFTI-1+ > > As you can see, the number of slices and volumes is extremely different between the two. Is there any way to use this field map with my DWI data for analysis using eddy? > > Thanks in advance! > > Michael ######################################################################## To unsubscribe from the FSL list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=FSL&A=1