Source code for fmriprep.workflows.fieldmap.fmap

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# emacs: -*- mode: python; py-indent-offset: 4; indent-tabs-mode: nil -*-
# vi: set ft=python sts=4 ts=4 sw=4 et:

.. _sdc_direct_b0 :

Direct B0 mapping sequences

When the fieldmap is directly measured with a prescribed sequence (such as
:abbr:`SE (spiral echo)`), we only need to calculate the corresponding B-Spline
coefficients to adapt the fieldmap to the TOPUP tool.
This procedure is described with more detail `here <\

This corresponds to the section 8.9.3 --fieldmap image (and one magnitude image)--
of the BIDS specification.


from niworkflows.nipype.pipeline import engine as pe
from niworkflows.nipype.interfaces import utility as niu, fsl, ants
# Note that deman_image imports from nipype
from niworkflows.nipype.workflows.dmri.fsl.utils import demean_image, cleanup_edge_pipeline
from niworkflows.interfaces.masks import BETRPT

from ...interfaces import (
    IntraModalMerge, DerivativesDataSink,
    FieldEnhance, FieldToRadS, FieldToHz

[docs]def init_fmap_wf(reportlets_dir, omp_nthreads, fmap_bspline, name='fmap_wf'): """ Fieldmap workflow - when we have a sequence that directly measures the fieldmap we just need to mask it (using the corresponding magnitude image) to remove the noise in the surrounding air region, and ensure that units are Hz. .. workflow :: :graph2use: orig :simple_form: yes from fmriprep.workflows.fieldmap.fmap import init_fmap_wf wf = init_fmap_wf(reportlets_dir='.', omp_nthreads=6, fmap_bspline=False) """ workflow = pe.Workflow(name=name) inputnode = pe.Node(niu.IdentityInterface( fields=['magnitude', 'fieldmap']), name='inputnode') outputnode = pe.Node(niu.IdentityInterface(fields=['fmap', 'fmap_ref', 'fmap_mask']), name='outputnode') # Merge input magnitude images magmrg = pe.Node(IntraModalMerge(), name='magmrg') # Merge input fieldmap images fmapmrg = pe.Node(IntraModalMerge(zero_based_avg=False, hmc=False), name='fmapmrg') # de-gradient the fields ("bias/illumination artifact") n4_correct = pe.Node(ants.N4BiasFieldCorrection(dimension=3, copy_header=True), name='n4_correct', n_procs=omp_nthreads) bet = pe.Node(BETRPT(generate_report=True, frac=0.6, mask=True), name='bet') ds_fmap_mask = pe.Node(DerivativesDataSink( base_directory=reportlets_dir, suffix='fmap_mask'), name='ds_fmap_mask', run_without_submitting=True) workflow.connect([ (inputnode, magmrg, [('magnitude', 'in_files')]), (inputnode, fmapmrg, [('fieldmap', 'in_files')]), (magmrg, n4_correct, [('out_file', 'input_image')]), (n4_correct, bet, [('output_image', 'in_file')]), (bet, outputnode, [('mask_file', 'fmap_mask'), ('out_file', 'fmap_ref')]), (inputnode, ds_fmap_mask, [('fieldmap', 'source_file')]), (bet, ds_fmap_mask, [('out_report', 'in_file')]), ]) if fmap_bspline: # despike_threshold=1.0, mask_erode=1), fmapenh = pe.Node(FieldEnhance(unwrap=False, despike=False), name='fmapenh', mem_gb=4, n_procs=omp_nthreads) workflow.connect([ (bet, fmapenh, [('mask_file', 'in_mask'), ('out_file', 'in_magnitude')]), (fmapmrg, fmapenh, [('out_file', 'in_file')]), (fmapenh, outputnode, [('out_file', 'fmap')]), ]) else: torads = pe.Node(FieldToRadS(), name='torads') prelude = pe.Node(fsl.PRELUDE(), name='prelude') tohz = pe.Node(FieldToHz(), name='tohz') denoise = pe.Node(fsl.SpatialFilter(operation='median', kernel_shape='sphere', kernel_size=3), name='denoise') demean = pe.Node(niu.Function(function=demean_image), name='demean') cleanup_wf = cleanup_edge_pipeline(name='cleanup_wf') applymsk = pe.Node(fsl.ApplyMask(), name='applymsk') workflow.connect([ (bet, prelude, [('mask_file', 'mask_file'), ('out_file', 'magnitude_file')]), (fmapmrg, torads, [('out_file', 'in_file')]), (torads, tohz, [('fmap_range', 'range_hz')]), (torads, prelude, [('out_file', 'phase_file')]), (prelude, tohz, [('unwrapped_phase_file', 'in_file')]), (tohz, denoise, [('out_file', 'in_file')]), (denoise, demean, [('out_file', 'in_file')]), (demean, cleanup_wf, [('out_file', 'inputnode.in_file')]), (bet, cleanup_wf, [('mask_file', 'inputnode.in_mask')]), (cleanup_wf, applymsk, [('outputnode.out_file', 'in_file')]), (bet, applymsk, [('mask_file', 'mask_file')]), (applymsk, outputnode, [('out_file', 'fmap')]), ]) return workflow