$ st_prepare_fieldmap -h

Usage: st_prepare_fieldmap [OPTIONS] PHASE...

Creates fieldmap (in Hz) from phase images.

This function accommodates multiple echoes (2 or more) and phase difference.
This function also accommodates 4D phase inputs, where the 4th dimension
represents the time, in case multiple field maps are acquired across time
for the purpose of real-time shimming experiments. For non Siemens phase
data, see --autoscale-phase option.

PHASE: Input path of phase nifti file(s), in ascending order: echo1, echo2,
etc.

Options:
--mag PATH                     Input path of mag nifti file  [required]
--unwrapper [prelude|skimage]  Algorithm for unwrapping. skimage is
                               installed by default, prelude requires FSL to
                               be installed.  [default: prelude]
-o, --output PATH              Output filename for the fieldmap, supported
                               types : '.nii', '.nii.gz'  [default:
                               ./fieldmap.nii.gz]
--autoscale-phase BOOLEAN      Tells whether to auto rescale phase inputs
                               according to manufacturer standards. If you
                               have non standard data, it would be
                               preferable to set this option to False and
                               input your phase data from -pi to pi to avoid
                               unwanted rescaling  [default: True]
--mask PATH                    Input path for a mask. Mask must be the same
                               shape as the array of each PHASE input.
--threshold FLOAT              Threshold for masking if no mask is provided.
                               Allowed range: [0, 1] where all scaled values
                               lower than the threshold are set to 0.
                               [default: 0.05]
--savemask PATH                Filename of the mask calculated by the
                               unwrapper
--gaussian-filter BOOLEAN      Gaussian filter for B0 map
--sigma FLOAT                  Standard deviation of gaussian filter. Used
                               for: gaussian_filter
-v, --verbose [info|debug]     Be more verbose
-h, --help                     Show this message and exit.