MRIQC measures

Structural images (sMRI)

The IQMs computed are as follows:

Identifier Reference Description
cnr
  cnr()
efc
  Entropy Focus Criterion
fber
  Foreground to Background Energy Ratio
fwhm
  Full-width half maximum smoothness of the voxels averaged across the three coordinate axes, and also for each axis
qi1
  Artifact Detection
snr
  Signal to Noise Ratio
bias_*
[Tustison2010] Summary measures of the bias field component estimated by N4ITK
rpve_*
  Residual Partial Volumes (rPVEs) of CSF, GM and WM.
icvs_*
  Intracranial volumes (ICVs) of CSF, GM and WM.
summary_mean_*
summary_stdv_*
summary_p05_*
summary_p95_*
  Mean, standard deviation, 5% percentile and 95% percentile of the distribution of background, CSF, GM and WM

Most of these IQMs are migrated or derivated from [QAP].

Functional images (fMRI)

The IQMs computed are as follows:

  1. efc Entropy Focus Criterion
  2. fber - Foreground to Background Energy Ratio
  3. fwhm - Full-width half maximum smoothness of the voxels averaged across the three coordinate axes, and also for each axis [x,y,x]
  4. ghost_x - Ghost to Signal Ratio
  5. snr - Signal to Noise Ratio
  6. dvars - Spatial standard deviation of the voxelwise temporal derivates
  7. gcor - Global Correlation
  8. mean_fd - Mean Fractional Displacement
  9. num_fd - Number of volumes with FD greater than 0.2mm
  10. perc_fd - Percent of volumes with FD greater than 0.2mm
  11. outlier - Mean fraction of outliers per fMRI volume
  12. quality - Median Distance Index
  13. summary_{mean, stdv, p05, p95}_* - Mean, standard deviation, 5% percentile and 95% percentile of the distribution of background and foreground.

References

[Tustison2010]Tustison NJ et al., N4ITK: improved N3 bias correction, IEEE Trans Med Imag, 29(6):1310-20, 2010. doi:10.1109/TMI.2010.2046908
[QAP]The Quality Assessment Protocols website: Taxonomy of QA Measures.