Motion Artifact Checker

Compute summed-absolute rigid framewise displacement with caller head-radius conversion and threshold; motion artifacts and motion correction quality are not diagnosed.

Description

Framewise displacement combines absolute changes in rigid translations with rotational changes converted to arc lengths at a supplied radius.

Framewise displacement combines absolute changes in rigid translations with rotational changes converted to arc lengths at a supplied radius. It summarizes consecutive-frame movement.

The tool returns framewiseDisplacementsMm (framewise displacements mm); flaggedFrameIndexes (flagged frame indexes). Input measurements and model parameters are supplied by the caller; the tool computes the stated summary rather than acquiring those measurements.

When to use Motion Artifact Checker

Use Motion Artifact Checker when you already have translationsMm, rotationsRadians, rotationRadiusMm, thresholdMm and want framewiseDisplacementsMm, flaggedFrameIndexes. This is useful for checking a supplied calculation, documenting a measurement convention, or comparing observations prepared on the same basis.

How to use Motion Artifact Checker and understand its results

Enter translationsMm, rotationsRadians, rotationRadiusMm, thresholdMm using the field table below. Match the units, ordering and data boundaries described in the calculation.
Run the tool after checking the stated bounds and matching paired observations or categories. A malformed request gives a tool error rather than a usable measurement.
Read framewiseDisplacementsMm, flaggedFrameIndexes. Use the calculation and interpretation below to distinguish amounts, ratios, signs and decision flags where applicable.
Review the supplied parameters and assumptions before using the result in a report or comparing it with another observation.

Input field	Meaning	Value type and bounds	Requirement
translationsMm	Translations mm	list of list of number	Required
rotationsRadians	Rotations radians	list of list of number	Required
rotationRadiusMm	Rotation radius mm	number	Required
thresholdMm	Threshold mm	number	Required

Require at least two aligned three-component frames. Flag strictly above the nonnegative threshold and return the original zero-based index of the later frame.

FD = Σ|ΔtranslationMm| + radiusMm×Σ|ΔrotationRadians|

The symbols refer to the supplied quantities or generated values described above; unit conversions and comparison boundaries follow the stated implementation.

json

{
  "input": {
    "translationsMm": [
      [
        0,
        0,
        0
      ],
      [
        1,
        0,
        0
      ],
      [
        1,
        0,
        0
      ]
    ],
    "rotationsRadians": [
      [
        0,
        0,
        0
      ],
      [
        0,
        0.01,
        0
      ],
      [
        0,
        0.01,
        0
      ]
    ],
    "rotationRadiusMm": 50,
    "thresholdMm": 1
  },
  "output": {
    "framewiseDisplacementsMm": [
      1.5,
      0
    ],
    "flaggedFrameIndexes": [
      1
    ]
  }
}

Limitations and assumptions

The first frame has no FD entry. No motion estimation, interpolation or automatic censoring is performed.

Numerical inputs must be finite. The tool checks its declared input shape and calculation constraints; those checks do not verify the quality, calibration or representativeness of the supplied observations.

Alternative or Complementary methods

Temporal SNR tSNR: Compute per-voxel temporal SNR using sample SD without detrending; constant series have undefined infinite tSNR and return an error, not a fabricated finite value. BOLD Percent Signal Change: Compute BOLD percent signal change from explicit disjoint sampled baseline/task windows; motion, drift and hemodynamic modeling are not performed.

Methodological background: Spurious but systematic correlations in functional connectivity MRI networks arise from subject motion.^[1]

References

Spurious but systematic correlations in functional connectivity MRI networks arise from subject motion — Power et al.; NeuroImage

Similar or alternative tools

Temporal SNR tSNR
Compute per-voxel temporal SNR using sample SD without detrending; constant series have undefined infinite tSNR and return an error, not a fabricated finite value.
BOLD Percent Signal Change
Compute BOLD percent signal change from explicit disjoint sampled baseline/task windows; motion, drift and hemodynamic modeling are not performed.