The effects of geometric distortion correction on motion realignment in fMRI

Mark A. Elliott, Eugene E. Gualtieri, Justin Hulvershorn, John D Ragland, Ruben Gur

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Subject motion is well recognized as a significant impediment to resolution and sensitivity in functional magnetic resonance imaging (fMRI). A parallel confounder to fMRI data quality is geometric image distortion, particularly at high field strengths, due to susceptibility-induced magnetic field inhomogeneity. Consequently, many high-field echo-planar imaging methods incorporate a post-processing distortion correction by acquiring a field map of the sample prior to the fMRI measurement. However, field mapping methods impose a spatial mask on the data, since field information is only obtainable from regions with adequate signal-to-noise ratio (SNR). This masking, when applied to subsequent images in the fMRI time series, can clip the effects of motion, resulting in inaccurate estimation and correction of motion-based changes in the images. The effects of geometric distortion correction on automated realignment (motion correction) of fMRI data are investigated from data acquired at 4 T. The results of image realignment with and without prior application of distortion correction are compared, using the estimated motion parameters and overall image realignment as metrics. The application of field-map-based distortion correction prior to image realignment reduces the amount of motion detected by a standard motion correction algorithm. Moreover, motion correction applied before distortion correction is shown to result in superior realignment of motion-correction images. It is preferable to perform motion realignment prior to correcting for geometric distortion.

Original languageEnglish (US)
Pages (from-to)1005-1010
Number of pages6
JournalAcademic Radiology
Issue number9
StatePublished - Sep 2004
Externally publishedYes


  • Artifact
  • brain
  • imaging
  • signal processing

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging


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