Generate Motion and Power Statistics

Functions for generating motion statistics

class CPAC.generate_motion_statistics.ImageTo1D(**inputs)

input_spec

alias of ImageTo1DInputSpec

output_spec

alias of ImageTo1DOutputSpec

CPAC.generate_motion_statistics.affine_file_from_params_file(params_file: str, affine_file: str | None = None) → str

Convert a 6-DOF motion parameters array into a 4x4 affine matrix.

Parameters:

• params_file (str) – path to a motion parameter file (6 DOF, one timepoint per line)

• affine_file (str) – path to a 4x4 affine matrix file (the first 12 values, one timepoint per line), optional If included, comments will be passed on to filtered affine file

Returns:

affine_file – path to a 4x4 affine matrix file (the first 12 values, one timepoint per line)

Return type:

str

CPAC.generate_motion_statistics.affine_from_params(params: ndarray) → ndarray

Convert a 6-DOF motion parameters array into a 4x4 affine matrix

Parameters:

params (np.ndarray) – 2-dimensional array (t x 6) with the first dimension as timepoints and the second dimension containing these 6 elements (as output by 3dvolreg -1Dfile): roll, pitch, yaw in degrees counterclockwise, and displacement in millimeters in the respective superior, left and posterior directions

Returns:

affine – t x 4 x 4 affine matrix with the upper-left 3 x 3 matrix encoding rotation, the top three values in the fourth column encoding translation and the bottom row being [0, 0, 0, 1] for each timepoint

Return type:

np.ndarray

CPAC.generate_motion_statistics.calculate_DVARS(func_brain, mask)

Method to calculate DVARS as per power’s method

Parameters:

• func_brain (string (nifti file)) – path to motion correct functional data

• mask (string (nifti file)) – path to brain only mask for functional data

Returns:

• out_file (string (numpy mat file)) – path to file containing array of DVARS calculation for each voxel

• dvars (array) – file containing array of DVARS calculation for each voxel

CPAC.generate_motion_statistics.calculate_FD_J(in_file: str, calc_from: Literal['affine', 'rms'], center: ndarray | None = None) → tuple[str, numpy.ndarray]

Method to calculate framewise displacement as per Jenkinson et al. 2002

Parameters:

• in_file (string) – matrix transformations from volume alignment file path if calc_from is ‘affine’, or FDRMS (*_rel.rms) output if calc_from is ‘rms’.

• calc_from (string) – one of {‘affine’, ‘rms’}

• center (ndarray, optional) – optional volume center for the from-affine calculation

Returns:

• out_file (string) – Framewise displacement file path

• fdj (ndarray) – Framewise displacement array

Examples

The file and array output by this function and the “rels_rms” property of the pickled test data (offset by a leading zero) should all be equal (rounded to the neareast 0.001): >>> import gzip, os, pickle >>> from unittest import mock >>> import numpy as np >>> with gzip.open(‘/code/CPAC/generate_motion_statistics/test/’ … ‘fdj_test_data.pklz’) as _pickle: … test_data = pickle.load(_pickle) >>> with mock.patch(‘nibabel.load’, … return_value=test_data.img), mock.patch( … ‘numpy.genfromtxt’, return_value=test_data.affine): … fdj_file, fdj = calculate_FD_J( … test_data.affine, calc_from=’affine’, … center=find_volume_center(test_data.img)) >>> fdj_from_file = np.genfromtxt(fdj_file) >>> fdj_test_data = np.insert(test_data.rels_rms, 0, 0) >>> all(np.isclose(fdj, fdj_from_file, atol=0.001)) True >>> all(np.isclose(fdj, fdj_test_data, atol=0.001)) True >>> all(np.isclose(fdj_from_file, fdj_test_data, atol=0.001)) True >>> os.unlink(fdj_file)

CPAC.generate_motion_statistics.calculate_FD_P(in_file)

Method to calculate Framewise Displacement (FD) as per Power et al., 2012

Parameters:

in_file (string) – movement parameters vector file path

Returns:

• out_file (string) – Frame-wise displacement mat file path

• fd (array) – Frame-wise displacement mat

CPAC.generate_motion_statistics.gen_motion_parameters(movement_parameters, max_displacement, motion_correct_tool, rels_displacement=None)

Method to calculate all the movement parameters

Parameters:

• max_displacement (string) – path of file with maximum displacement (in mm) for brain voxels in each volume

• movement_parameters (string) – path of 1D file containing six movement/motion parameters (3 Translation, 3 Rotations) in different columns (roll pitch yaw dS dL dP)

Returns:

• out_file (string) – path to csv file containing various motion parameters

• info (text) – contains information about motion parameters

• maxdisp (array) – max displacement value

• relsdisp (array) – rels displacement value

CPAC.generate_motion_statistics.gen_power_parameters(fdp=None, fdj=None, dvars=None, motion_correct_tool='3dvolreg')

Method to generate Power parameters for scrubbing

Parameters:

• fdp (string) – framewise displacement(FD as per power et al., 2012) file path

• fdj (string) – framewise displacement(FD as per jenkinson et al., 2002) file path

• dvars (string) – path to numpy file containing DVARS

Returns:

• out_file (string (csv file)) – path to csv file containing all the pow parameters

• info (text) – contains information about power parameters

CPAC.generate_motion_statistics.motion_power_statistics(name='motion_stats', motion_correct_tool='3dvolreg', filtered=False)

The main purpose of this workflow is to get various statistical measures

from the movement/motion parameters obtained in functional preprocessing.

:param : :type : param str name: Name of the workflow, defaults to 'motion_stats' :param : :type : return: Nuisance workflow. :param : :type : rtype: nipype.pipeline.engine.Workflow

Notes

Workflow Inputs:

inputspec.motion_correct : string (func/rest file or a list of func/rest nifti file)
    Path to motion corrected functional data

inputspec.max_displacement : string (Mat file)
    maximum displacement (in mm) vector for brain voxels in each volume.
    This file is obtained in functional preprocessing step

inputspec.movement_parameters : string (Mat file)
    1D file containing six movement/motion parameters(3 Translation, 3 Rotations)
    in different columns (roll pitch yaw dS  dL  dP), obtained in functional preprocessing step

Workflow Outputs:

outputspec.FDP_1D : 1D file
    mean Framewise Displacement (FD)

outputspec.power_params : txt file
    Text file containing various power parameters for scrubbing

outputspec.motion_params : txt file
    Text file containing various movement parameters

Order of commands:

• Calculate Framewise Displacement FD as per power et al., 2012

  Differentiating head realignment parameters across frames yields a six dimensional timeseries that represents instantaneous head motion. Rotational displacements are converted from degrees to millimeters by calculating displacement on the surface of a sphere of radius 50 mm.[R5]

• Calculate Framewise Displacement FD as per jenkinson et al., 2002

• Calculate DVARS

  DVARS (D temporal derivative of timecourses, VARS referring to RMS variance over voxels) indexes the rate of change of BOLD signal across the entire brain at each frame of data.To calculate DVARS, the volumetric timeseries is differentiated (by backwards differences) and RMS signal change is calculated over the whole brain.DVARS is thus a measure of how much the intensity of a brain image changes in comparison to the previous timepoint (as opposed to the global signal, which is the average value of a brain image at a timepoint).[R5]

• Calculate Power parameters:

  MeanFD : Mean (across time/frames) of the absolute values for Framewise Displacement (FD),
  computed as described in Power et al., Neuroimage, 2012)
  
  rootMeanSquareFD : Root mean square (RMS; across time/frames) of the absolute values for FD
  
  rmsFD : Root mean square (RMS; across time/frames) of the absolute values for FD
  
  FDquartile(top 1/4th FD) : Mean of the top 25% highest FD values
  
  MeanDVARS : Mean of voxel DVARS
  

• Calculate Motion Parameters

  Following motion parameters are calculated:

  Scan
  Mean Relative RMS Displacement
  Max Relative RMS Displacement
  Movements > threshold
  Mean Relative Mean Rotation
  Mean Relative Maxdisp
  Max Relative Maxdisp
  Max Abs Maxdisp
  Max Relative Roll
  Max Relative Pitch
  Max Relative Yaw
  Max Relative dS-I
  Max Relative dL-R
  Max Relative dP-A
  Mean Relative Roll
  Mean Relative Pitch
  Mean Relative Yaw
  Mean Relative dS-I
  Mean Relative dL-R
  Mean Relative dP-A
  Max Abs Roll
  Max Abs Pitch
  Max Abs Yaw
  Max Abs dS-I
  Max Abs dL-R
  Max Abs dP-A
  Mean Abs Roll
  Mean Abs Pitch
  Mean Abs Yaw
  Mean Abs dS-I
  Mean Abs dL-R
  Mean Abs dP-A
  

High Level Workflow Graph:

Detailed Workflow Graph:

Examples

>>> from CPAC import generate_motion_statistics
>>> wf = generate_motion_statistics.motion_power_statistics("generate_statistics")
>>> wf.inputs.inputspec.movement_parameters = 'CPAC_outupts/sub01/func/movement_parameteres/rest_mc.1D'  
>>> wf.inputs.inputspec.max_displacement = 'CPAC_outputs/sub01/func/max_dispalcement/max_disp.1D'  
>>> wf.inputs.inputspec.motion_correct = 'CPAC_outputs/sub01/func/motion_correct/rest_mc.nii.gz'  
>>> wf.inputs.inputspec.mask = 'CPAC_outputs/sub01/func/func_mask/rest_mask.nii.gz'  
>>> wf.inputs.inputspec.transformations = 'CPAC_outputs/sub01/func/coordinate_transformation/rest_mc.aff12.1D'  
>>> wf.base_dir = './working_dir'  
>>> wf.run()  

References

[1]

Power, J. D., Barnes, K. A., Snyder, A. Z., Schlaggar, B. L., & Petersen, S. E. (2012). Spurious but systematic correlations in functional connectivity MRI networks arise from subject motion. NeuroImage, 59(3), 2142-2154. doi:10.1016/j.neuroimage.2011.10.018

[2]

Power, J. D., Barnes, K. A., Snyder, A. Z., Schlaggar, B. L., & Petersen, S. E. (2012). Steps toward optimizing motion artifact removal in functional connectivity MRI; a reply to Carp. NeuroImage. doi:10.1016/j.neuroimage.2012.03.017

[3]

Jenkinson, M., Bannister, P., Brady, M., Smith, S., 2002. Improved optimization for the robust and accurate linear registration and motion correction of brain images. Neuroimage 17, 825-841.