def test_SimpleBeforeAfterRPT(reference, moving):
    """ the SimpleBeforeAfterRPT report capable test """
    flirt_rpt = FLIRTRPT(generate_report=False, in_file=moving,
                         reference=reference)

    ba_rpt = SimpleBeforeAfterRPT(
        generate_report=True,
        before=reference,
        after=flirt_rpt.run().outputs.out_file
    )
    _smoke_test_report(ba_rpt, 'test_SimpleBeforeAfterRPT.svg')
def test_ApplyXFMRPT(reference, moving):
    """ the ApplyXFM report capable test """
    flirt_rpt = FLIRTRPT(generate_report=False, in_file=moving,
                         reference=reference)

    applyxfm_rpt = ApplyXFMRPT(
        generate_report=True,
        in_file=moving,
        in_matrix_file=flirt_rpt.run().outputs.out_matrix_file,
        reference=reference,
        apply_xfm=True
    )
    _smoke_test_report(applyxfm_rpt, 'testApplyXFM.svg')
Example #3
0
def test_FLIRTRPT_w_BBR(reference, reference_mask, moving):
    """ test FLIRTRPT with input `wm_seg` set.
    For the sake of testing ONLY, `wm_seg` is set to the filename of a brain mask """
    flirt_rpt = FLIRTRPT(generate_report=True,
                         in_file=moving,
                         reference=reference,
                         wm_seg=reference_mask)
    _smoke_test_report(flirt_rpt, 'testFLIRTRPTBBR.svg')
Example #4
0
 def test_FLIRTRPT(self):
     """ the FLIRT report capable test """
     flirt_rpt = FLIRTRPT(generate_report=True,
                          in_file=self.moving,
                          reference=self.reference)
     _smoke_test_report(flirt_rpt, 'testFLIRT.svg')
def init_fsl_bbr_wf(use_bbr,
                    bold2t1w_dof,
                    bold2t1w_init,
                    sloppy=False,
                    name='fsl_bbr_wf'):
    """
    Build a workflow to run FSL's ``flirt``.

    This workflow uses FSL FLIRT to register a BOLD image to a T1-weighted
    structural image, using a boundary-based registration (BBR) cost function.
    It is a counterpart to :py:func:`~fmriprep.workflows.bold.registration.init_bbreg_wf`,
    which performs the same task using FreeSurfer's ``bbregister``.

    The ``use_bbr`` option permits a high degree of control over registration.
    If ``False``, standard, rigid coregistration will be performed by FLIRT.
    If ``True``, FLIRT-BBR will be seeded with the initial transform found by
    the rigid coregistration.
    If ``None``, after FLIRT-BBR is run, the resulting affine transform
    will be compared to the initial transform found by FLIRT.
    Excessive deviation will result in rejecting the BBR refinement and
    accepting the original, affine registration.

    Workflow Graph
        .. workflow ::
            :graph2use: orig
            :simple_form: yes

            from fmriprep.workflows.bold.registration import init_fsl_bbr_wf
            wf = init_fsl_bbr_wf(use_bbr=True, bold2t1w_dof=9, bold2t1w_init='register')


    Parameters
    ----------
    use_bbr : :obj:`bool` or None
        Enable/disable boundary-based registration refinement.
        If ``None``, test BBR result for distortion before accepting.
    bold2t1w_dof : 6, 9 or 12
        Degrees-of-freedom for BOLD-T1w registration
    bold2t1w_init : str, 'header' or 'register'
        If ``'header'``, use header information for initialization of BOLD and T1 images.
        If ``'register'``, align volumes by their centers.
    name : :obj:`str`, optional
        Workflow name (default: fsl_bbr_wf)

    Inputs
    ------
    in_file
        Reference BOLD image to be registered
    t1w_brain
        Skull-stripped T1-weighted structural image
    t1w_dseg
        FAST segmentation of ``t1w_brain``
    fsnative2t1w_xfm
        Unused (see :py:func:`~fmriprep.workflows.bold.registration.init_bbreg_wf`)
    subjects_dir
        Unused (see :py:func:`~fmriprep.workflows.bold.registration.init_bbreg_wf`)
    subject_id
        Unused (see :py:func:`~fmriprep.workflows.bold.registration.init_bbreg_wf`)

    Outputs
    -------
    itk_bold_to_t1
        Affine transform from ``ref_bold_brain`` to T1w space (ITK format)
    itk_t1_to_bold
        Affine transform from T1 space to BOLD space (ITK format)
    out_report
        Reportlet for assessing registration quality
    fallback
        Boolean indicating whether BBR was rejected (rigid FLIRT registration returned)

    """
    from niworkflows.engine.workflows import LiterateWorkflow as Workflow
    from niworkflows.utils.images import dseg_label as _dseg_label
    from niworkflows.interfaces.freesurfer import PatchedLTAConvert as LTAConvert
    from niworkflows.interfaces.registration import FLIRTRPT
    workflow = Workflow(name=name)
    workflow.__desc__ = """\
The BOLD reference was then co-registered to the T1w reference using
`flirt` [FSL {fsl_ver}, @flirt] with the boundary-based registration [@bbr]
cost-function.
Co-registration was configured with nine degrees of freedom to account
for distortions remaining in the BOLD reference.
""".format(fsl_ver=FLIRTRPT().version or '<ver>')

    inputnode = pe.Node(
        niu.IdentityInterface([
            'in_file',
            'fsnative2t1w_xfm',
            'subjects_dir',
            'subject_id',  # BBRegister
            't1w_dseg',
            't1w_brain'
        ]),  # FLIRT BBR
        name='inputnode')
    outputnode = pe.Node(niu.IdentityInterface(
        ['itk_bold_to_t1', 'itk_t1_to_bold', 'out_report', 'fallback']),
                         name='outputnode')

    wm_mask = pe.Node(niu.Function(function=_dseg_label), name='wm_mask')
    wm_mask.inputs.label = 2  # BIDS default is WM=2
    flt_bbr_init = pe.Node(FLIRTRPT(dof=6,
                                    generate_report=not use_bbr,
                                    uses_qform=True),
                           name='flt_bbr_init')

    if bold2t1w_init not in ("register", "header"):
        raise ValueError(
            f"Unknown BOLD-T1w initialization option: {bold2t1w_init}")

    if bold2t1w_init == "header":
        raise NotImplementedError(
            "Header-based registration initialization not supported for FSL")

    invt_bbr = pe.Node(fsl.ConvertXFM(invert_xfm=True),
                       name='invt_bbr',
                       mem_gb=DEFAULT_MEMORY_MIN_GB)

    # BOLD to T1 transform matrix is from fsl, using c3 tools to convert to
    # something ANTs will like.
    fsl2itk_fwd = pe.Node(c3.C3dAffineTool(fsl2ras=True, itk_transform=True),
                          name='fsl2itk_fwd',
                          mem_gb=DEFAULT_MEMORY_MIN_GB)
    fsl2itk_inv = pe.Node(c3.C3dAffineTool(fsl2ras=True, itk_transform=True),
                          name='fsl2itk_inv',
                          mem_gb=DEFAULT_MEMORY_MIN_GB)

    workflow.connect([
        (inputnode, flt_bbr_init, [('in_file', 'in_file'),
                                   ('t1w_brain', 'reference')]),
        (inputnode, fsl2itk_fwd, [('t1w_brain', 'reference_file'),
                                  ('in_file', 'source_file')]),
        (inputnode, fsl2itk_inv, [('in_file', 'reference_file'),
                                  ('t1w_brain', 'source_file')]),
        (invt_bbr, fsl2itk_inv, [('out_file', 'transform_file')]),
        (fsl2itk_fwd, outputnode, [('itk_transform', 'itk_bold_to_t1')]),
        (fsl2itk_inv, outputnode, [('itk_transform', 'itk_t1_to_bold')]),
    ])

    # Short-circuit workflow building, use rigid registration
    if use_bbr is False:
        workflow.connect([
            (flt_bbr_init, invt_bbr, [('out_matrix_file', 'in_file')]),
            (flt_bbr_init, fsl2itk_fwd, [('out_matrix_file', 'transform_file')
                                         ]),
            (flt_bbr_init, outputnode, [('out_report', 'out_report')]),
        ])
        outputnode.inputs.fallback = True

        return workflow

    flt_bbr = pe.Node(FLIRTRPT(cost_func='bbr',
                               dof=bold2t1w_dof,
                               generate_report=True),
                      name='flt_bbr')

    FSLDIR = os.getenv('FSLDIR')
    if FSLDIR:
        flt_bbr.inputs.schedule = op.join(FSLDIR, 'etc/flirtsch/bbr.sch')
    else:
        # Should mostly be hit while building docs
        LOGGER.warning("FSLDIR unset - using packaged BBR schedule")
        flt_bbr.inputs.schedule = pkgr.resource_filename(
            'fmriprep', 'data/flirtsch/bbr.sch')

    workflow.connect([
        (inputnode, wm_mask, [('t1w_dseg', 'in_seg')]),
        (inputnode, flt_bbr, [('in_file', 'in_file')]),
        (flt_bbr_init, flt_bbr, [('out_matrix_file', 'in_matrix_file')]),
    ])

    if sloppy is True:
        downsample = pe.Node(niu.Function(
            function=_conditional_downsampling,
            output_names=["out_file", "out_mask"]),
                             name='downsample')
        workflow.connect([
            (inputnode, downsample, [("t1w_brain", "in_file")]),
            (wm_mask, downsample, [("out", "in_mask")]),
            (downsample, flt_bbr, [('out_file', 'reference'),
                                   ('out_mask', 'wm_seg')]),
        ])
    else:
        workflow.connect([
            (inputnode, flt_bbr, [('t1w_brain', 'reference')]),
            (wm_mask, flt_bbr, [('out', 'wm_seg')]),
        ])

    # Short-circuit workflow building, use boundary-based registration
    if use_bbr is True:
        workflow.connect([
            (flt_bbr, invt_bbr, [('out_matrix_file', 'in_file')]),
            (flt_bbr, fsl2itk_fwd, [('out_matrix_file', 'transform_file')]),
            (flt_bbr, outputnode, [('out_report', 'out_report')]),
        ])
        outputnode.inputs.fallback = False

        return workflow

    transforms = pe.Node(niu.Merge(2),
                         run_without_submitting=True,
                         name='transforms')
    reports = pe.Node(niu.Merge(2),
                      run_without_submitting=True,
                      name='reports')

    compare_transforms = pe.Node(niu.Function(function=compare_xforms),
                                 name='compare_transforms')

    select_transform = pe.Node(niu.Select(),
                               run_without_submitting=True,
                               name='select_transform')
    select_report = pe.Node(niu.Select(),
                            run_without_submitting=True,
                            name='select_report')

    fsl_to_lta = pe.MapNode(LTAConvert(out_lta=True),
                            iterfield=['in_fsl'],
                            name='fsl_to_lta')

    workflow.connect([
        (flt_bbr, transforms, [('out_matrix_file', 'in1')]),
        (flt_bbr_init, transforms, [('out_matrix_file', 'in2')]),
        # Convert FSL transforms to LTA (RAS2RAS) transforms and compare
        (inputnode, fsl_to_lta, [('in_file', 'source_file'),
                                 ('t1w_brain', 'target_file')]),
        (transforms, fsl_to_lta, [('out', 'in_fsl')]),
        (fsl_to_lta, compare_transforms, [('out_lta', 'lta_list')]),
        (compare_transforms, outputnode, [('out', 'fallback')]),
        # Select output transform
        (transforms, select_transform, [('out', 'inlist')]),
        (compare_transforms, select_transform, [('out', 'index')]),
        (select_transform, invt_bbr, [('out', 'in_file')]),
        (select_transform, fsl2itk_fwd, [('out', 'transform_file')]),
        (flt_bbr, reports, [('out_report', 'in1')]),
        (flt_bbr_init, reports, [('out_report', 'in2')]),
        (reports, select_report, [('out', 'inlist')]),
        (compare_transforms, select_report, [('out', 'index')]),
        (select_report, outputnode, [('out', 'out_report')]),
    ])

    return workflow
Example #6
0
def init_fsl_bbr_wf(use_bbr, bold2t1w_dof, name='fsl_bbr_wf'):
    """
    This workflow uses FSL FLIRT to register a BOLD image to a T1-weighted
    structural image, using a boundary-based registration (BBR) cost function.

    It is a counterpart to :py:func:`~fmriprep.workflows.bold.registration.init_bbreg_wf`,
    which performs the same task using FreeSurfer's ``bbregister``.

    The ``use_bbr`` option permits a high degree of control over registration.
    If ``False``, standard, rigid coregistration will be performed by FLIRT.
    If ``True``, FLIRT-BBR will be seeded with the initial transform found by
    the rigid coregistration.
    If ``None``, after FLIRT-BBR is run, the resulting affine transform
    will be compared to the initial transform found by FLIRT.
    Excessive deviation will result in rejecting the BBR refinement and
    accepting the original, affine registration.

    .. workflow ::
        :graph2use: orig
        :simple_form: yes

        from fmriprep.workflows.bold.registration import init_fsl_bbr_wf
        wf = init_fsl_bbr_wf(use_bbr=True, bold2t1w_dof=9)


    Parameters

        use_bbr : bool or None
            Enable/disable boundary-based registration refinement.
            If ``None``, test BBR result for distortion before accepting.
        bold2t1w_dof : 6, 9 or 12
            Degrees-of-freedom for BOLD-T1w registration
        name : str, optional
            Workflow name (default: fsl_bbr_wf)


    Inputs

        in_file
            Reference BOLD image to be registered
        t1_brain
            Skull-stripped T1-weighted structural image
        t1_seg
            FAST segmentation of ``t1_brain``
        t1_2_fsnative_reverse_transform
            Unused (see :py:func:`~fmriprep.workflows.util.init_bbreg_wf`)
        subjects_dir
            Unused (see :py:func:`~fmriprep.workflows.util.init_bbreg_wf`)
        subject_id
            Unused (see :py:func:`~fmriprep.workflows.util.init_bbreg_wf`)


    Outputs

        itk_bold_to_t1
            Affine transform from ``ref_bold_brain`` to T1 space (ITK format)
        itk_t1_to_bold
            Affine transform from T1 space to BOLD space (ITK format)
        out_report
            Reportlet for assessing registration quality
        fallback
            Boolean indicating whether BBR was rejected (rigid FLIRT registration returned)

    """
    workflow = Workflow(name=name)
    workflow.__desc__ = """\
The BOLD reference was then co-registered to the T1w reference using
`flirt` [FSL {fsl_ver}, @flirt] with the boundary-based registration [@bbr]
cost-function.
Co-registration was configured with nine degrees of freedom to account
for distortions remaining in the BOLD reference.
""".format(fsl_ver=FLIRTRPT().version or '<ver>')

    inputnode = pe.Node(
        niu.IdentityInterface([
            'in_file',
            't1_2_fsnative_reverse_transform',
            'subjects_dir',
            'subject_id',  # BBRegister
            't1_seg',
            't1_brain'
        ]),  # FLIRT BBR
        name='inputnode')
    outputnode = pe.Node(niu.IdentityInterface(
        ['itk_bold_to_t1', 'itk_t1_to_bold', 'out_report', 'fallback']),
                         name='outputnode')

    wm_mask = pe.Node(niu.Function(function=extract_wm), name='wm_mask')
    flt_bbr_init = pe.Node(FLIRTRPT(dof=6,
                                    generate_report=not use_bbr,
                                    uses_qform=True),
                           name='flt_bbr_init')

    invt_bbr = pe.Node(fsl.ConvertXFM(invert_xfm=True),
                       name='invt_bbr',
                       mem_gb=DEFAULT_MEMORY_MIN_GB)

    #  BOLD to T1 transform matrix is from fsl, using c3 tools to convert to
    #  something ANTs will like.
    fsl2itk_fwd = pe.Node(c3.C3dAffineTool(fsl2ras=True, itk_transform=True),
                          name='fsl2itk_fwd',
                          mem_gb=DEFAULT_MEMORY_MIN_GB)
    fsl2itk_inv = pe.Node(c3.C3dAffineTool(fsl2ras=True, itk_transform=True),
                          name='fsl2itk_inv',
                          mem_gb=DEFAULT_MEMORY_MIN_GB)

    workflow.connect([
        (inputnode, flt_bbr_init, [('in_file', 'in_file'),
                                   ('t1_brain', 'reference')]),
        (inputnode, fsl2itk_fwd, [('t1_brain', 'reference_file'),
                                  ('in_file', 'source_file')]),
        (inputnode, fsl2itk_inv, [('in_file', 'reference_file'),
                                  ('t1_brain', 'source_file')]),
        (invt_bbr, fsl2itk_inv, [('out_file', 'transform_file')]),
        (fsl2itk_fwd, outputnode, [('itk_transform', 'itk_bold_to_t1')]),
        (fsl2itk_inv, outputnode, [('itk_transform', 'itk_t1_to_bold')]),
    ])

    # Short-circuit workflow building, use rigid registration
    if use_bbr is False:
        workflow.connect([
            (flt_bbr_init, invt_bbr, [('out_matrix_file', 'in_file')]),
            (flt_bbr_init, fsl2itk_fwd, [('out_matrix_file', 'transform_file')
                                         ]),
            (flt_bbr_init, outputnode, [('out_report', 'out_report')]),
        ])
        outputnode.inputs.fallback = True

        return workflow

    flt_bbr = pe.Node(FLIRTRPT(cost_func='bbr',
                               dof=bold2t1w_dof,
                               generate_report=True,
                               schedule=op.join(os.getenv('FSLDIR'),
                                                'etc/flirtsch/bbr.sch')),
                      name='flt_bbr')

    workflow.connect([
        (inputnode, wm_mask, [('t1_seg', 'in_seg')]),
        (inputnode, flt_bbr, [('in_file', 'in_file'),
                              ('t1_brain', 'reference')]),
        (flt_bbr_init, flt_bbr, [('out_matrix_file', 'in_matrix_file')]),
        (wm_mask, flt_bbr, [('out', 'wm_seg')]),
    ])

    # Short-circuit workflow building, use boundary-based registration
    if use_bbr is True:
        workflow.connect([
            (flt_bbr, invt_bbr, [('out_matrix_file', 'in_file')]),
            (flt_bbr, fsl2itk_fwd, [('out_matrix_file', 'transform_file')]),
            (flt_bbr, outputnode, [('out_report', 'out_report')]),
        ])
        outputnode.inputs.fallback = False

        return workflow

    transforms = pe.Node(niu.Merge(2),
                         run_without_submitting=True,
                         name='transforms')
    reports = pe.Node(niu.Merge(2),
                      run_without_submitting=True,
                      name='reports')

    compare_transforms = pe.Node(niu.Function(function=compare_xforms),
                                 name='compare_transforms')

    select_transform = pe.Node(niu.Select(),
                               run_without_submitting=True,
                               name='select_transform')
    select_report = pe.Node(niu.Select(),
                            run_without_submitting=True,
                            name='select_report')

    fsl_to_lta = pe.MapNode(fs.utils.LTAConvert(out_lta=True),
                            iterfield=['in_fsl'],
                            name='fsl_to_lta')

    workflow.connect([
        (flt_bbr, transforms, [('out_matrix_file', 'in1')]),
        (flt_bbr_init, transforms, [('out_matrix_file', 'in2')]),
        # Convert FSL transforms to LTA (RAS2RAS) transforms and compare
        (inputnode, fsl_to_lta, [('in_file', 'source_file'),
                                 ('t1_brain', 'target_file')]),
        (transforms, fsl_to_lta, [('out', 'in_fsl')]),
        (fsl_to_lta, compare_transforms, [('out_lta', 'lta_list')]),
        (compare_transforms, outputnode, [('out', 'fallback')]),
        # Select output transform
        (transforms, select_transform, [('out', 'inlist')]),
        (compare_transforms, select_transform, [('out', 'index')]),
        (select_transform, invt_bbr, [('out', 'in_file')]),
        (select_transform, fsl2itk_fwd, [('out', 'transform_file')]),
        (flt_bbr, reports, [('out_report', 'in1')]),
        (flt_bbr_init, reports, [('out_report', 'in2')]),
        (reports, select_report, [('out', 'inlist')]),
        (compare_transforms, select_report, [('out', 'index')]),
        (select_report, outputnode, [('out', 'out_report')]),
    ])

    return workflow
def test_FLIRTRPT(reference, moving):
    """ the FLIRT report capable test """
    flirt_rpt = FLIRTRPT(generate_report=True,
                         in_file=moving,
                         reference=reference)
    _smoke_test_report(flirt_rpt, "testFLIRT.svg")
Example #8
0
def init_epi_reg_wf(freesurfer, bold2t1w_dof,
                    bold_file_size_gb, output_spaces, output_dir,
                    name='epi_reg_wf', use_fieldwarp=False):
    """
    Uses FSL FLIRT with the BBR cost function to find the transform that
    maps the EPI space into the T1-space
    """
    workflow = pe.Workflow(name=name)
    inputnode = pe.Node(
        niu.IdentityInterface(fields=['name_source', 'ref_epi_brain', 'ref_epi_mask',
                                      't1_preproc', 't1_brain', 't1_mask',
                                      't1_seg', 'epi_split', 'hmc_xforms',
                                      'subjects_dir', 'subject_id', 'fs_2_t1_transform',
                                      'fieldwarp']),
        name='inputnode'
    )
    outputnode = pe.Node(
        niu.IdentityInterface(fields=['mat_epi_to_t1', 'mat_t1_to_epi',
                                      'itk_epi_to_t1', 'itk_t1_to_epi',
                                      'epi_t1', 'epi_mask_t1', 'fs_reg_file',
                                      'out_report']),
        name='outputnode'
    )

    if freesurfer:
        bbregister = pe.Node(
            BBRegisterRPT(
                dof=bold2t1w_dof,
                contrast_type='t2',
                init='coreg',
                registered_file=True,
                out_fsl_file=True,
                generate_report=True),
            name='bbregister'
            )

        def apply_fs_transform(fs_2_t1_transform, bbreg_transform):
            import os
            import numpy as np
            out_file = os.path.abspath('transform.mat')
            fs_xfm = np.loadtxt(fs_2_t1_transform)
            bbrxfm = np.loadtxt(bbreg_transform)
            out_xfm = fs_xfm.dot(bbrxfm)
            assert np.allclose(out_xfm[3], [0, 0, 0, 1])
            out_xfm[3] = [0, 0, 0, 1]
            np.savetxt(out_file, out_xfm, fmt='%.12g')
            return out_file

        transformer = pe.Node(niu.Function(function=apply_fs_transform),
                              name='transformer', run_without_submitting=True)
    else:
        wm_mask = pe.Node(niu.Function(function=_extract_wm), name='wm_mask')
        flt_bbr_init = pe.Node(FLIRTRPT(generate_report=True, dof=6), name='flt_bbr_init')
        flt_bbr = pe.Node(
            FLIRTRPT(generate_report=True, cost_func='bbr',
                     dof=bold2t1w_dof),
            name='flt_bbr')
        flt_bbr.inputs.schedule = op.join(os.getenv('FSLDIR'),
                                          'etc/flirtsch/bbr.sch')

    # make equivalent warp fields
    invt_bbr = pe.Node(fsl.ConvertXFM(invert_xfm=True), name='invt_bbr')

    #  EPI to T1 transform matrix is from fsl, using c3 tools to convert to
    #  something ANTs will like.
    fsl2itk_fwd = pe.Node(c3.C3dAffineTool(fsl2ras=True, itk_transform=True),
                          name='fsl2itk_fwd')
    fsl2itk_inv = pe.Node(c3.C3dAffineTool(fsl2ras=True, itk_transform=True),
                          name='fsl2itk_inv')

    workflow.connect([
        (inputnode, fsl2itk_fwd, [('t1_preproc', 'reference_file'),
                                  ('ref_epi_brain', 'source_file')]),
        (inputnode, fsl2itk_inv, [('ref_epi_brain', 'reference_file'),
                                  ('t1_preproc', 'source_file')]),
        (invt_bbr, outputnode, [('out_file', 'mat_t1_to_epi')]),
        (invt_bbr, fsl2itk_inv, [('out_file', 'transform_file')]),
        (fsl2itk_fwd, outputnode, [('itk_transform', 'itk_epi_to_t1')]),
        (fsl2itk_inv, outputnode, [('itk_transform', 'itk_t1_to_epi')]),
    ])

    gen_ref = pe.Node(GenerateSamplingReference(), name='gen_ref')

    mask_t1w_tfm = pe.Node(
        ants.ApplyTransforms(interpolation='NearestNeighbor',
                             float=True),
        name='mask_t1w_tfm'
    )

    workflow.connect([
        (inputnode, gen_ref, [('ref_epi_brain', 'moving_image'),
                              ('t1_brain', 'fixed_image')]),
        (gen_ref, mask_t1w_tfm, [('out_file', 'reference_image')]),
        (fsl2itk_fwd, mask_t1w_tfm, [('itk_transform', 'transforms')]),
        (inputnode, mask_t1w_tfm, [('ref_epi_mask', 'input_image')]),
        (mask_t1w_tfm, outputnode, [('output_image', 'epi_mask_t1')])
    ])

    if use_fieldwarp:
        merge_transforms = pe.MapNode(niu.Merge(3), iterfield=['in3'],
                                      name='merge_transforms', run_without_submitting=True)
        workflow.connect([
            (inputnode, merge_transforms, [('fieldwarp', 'in2'),
                                           ('hmc_xforms', 'in3')])
            ])
    else:
        merge_transforms = pe.MapNode(niu.Merge(2), iterfield=['in2'],
                                      name='merge_transforms', run_without_submitting=True)
        workflow.connect([
            (inputnode, merge_transforms, [('hmc_xforms', 'in2')])
        ])

    merge = pe.Node(Merge(), name='merge')
    merge.interface.estimated_memory_gb = bold_file_size_gb * 3

    epi_to_t1w_transform = pe.MapNode(
        ants.ApplyTransforms(interpolation="LanczosWindowedSinc",
                             float=True),
        iterfield=['input_image', 'transforms'],
        name='epi_to_t1w_transform')
    epi_to_t1w_transform.terminal_output = 'file'

    workflow.connect([
        (fsl2itk_fwd, merge_transforms, [('itk_transform', 'in1')]),
        (merge_transforms, epi_to_t1w_transform, [('out', 'transforms')]),
        (epi_to_t1w_transform, merge, [('output_image', 'in_files')]),
        (inputnode, merge, [('name_source', 'header_source')]),
        (merge, outputnode, [('out_file', 'epi_t1')]),
        (inputnode, epi_to_t1w_transform, [('epi_split', 'input_image')]),
        (gen_ref, epi_to_t1w_transform, [('out_file', 'reference_image')]),
    ])

    if freesurfer:
        workflow.connect([
            (inputnode, bbregister, [('subjects_dir', 'subjects_dir'),
                                     ('subject_id', 'subject_id')]),
            (inputnode, bbregister, [('ref_epi_brain', 'source_file')]),
            (inputnode, transformer, [('fs_2_t1_transform', 'fs_2_t1_transform')]),
            (bbregister, transformer, [('out_fsl_file', 'bbreg_transform')]),
            (transformer, invt_bbr, [('out', 'in_file')]),
            (transformer, fsl2itk_fwd, [('out', 'transform_file')]),
            (transformer, outputnode, [('out', 'mat_epi_to_t1')]),
            (bbregister, outputnode, [('out_reg_file', 'fs_reg_file'),
                                      ('out_report', 'out_report')]),
        ])
    else:
        workflow.connect([
            (inputnode, wm_mask, [('t1_seg', 'in_file')]),
            (inputnode, flt_bbr_init, [('ref_epi_brain', 'in_file')]),
            (inputnode, flt_bbr_init, [('t1_brain', 'reference')]),
            (flt_bbr_init, flt_bbr, [('out_matrix_file', 'in_matrix_file')]),
            (inputnode, flt_bbr, [('t1_brain', 'reference')]),
            (inputnode, flt_bbr, [('ref_epi_brain', 'in_file')]),
            (wm_mask, flt_bbr, [('out', 'wm_seg')]),
            (flt_bbr, invt_bbr, [('out_matrix_file', 'in_file')]),
            (flt_bbr, fsl2itk_fwd, [('out_matrix_file', 'transform_file')]),
            (flt_bbr, outputnode, [('out_matrix_file', 'mat_epi_to_t1'),
                                   ('out_report', 'out_report')]),
        ])

    return workflow