Reference-free unwarping of EPI data using dynamic off-resonance correction with multiecho acquisition (DOCMA)

Eelke Visser*, Benedikt A Poser, Markus Barth, Marcel P Zwiers

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review


Inhomogeneities of the main magnetic field cause geometric distortion in echo-planar imaging, a method central to functional MRI. A number of correction methods have been proposed, most of which are based on the acquisition of a fieldmap providing the local offsets to the main magnetic field. Here, accelerated multiecho echo-planar imaging is used, with echo times short enough to enable the construction of a fieldmap of comparable quality from the data themselves. This way, each volume in a time series can be unwarped using a fieldmap obtained from that volume, avoiding volume-to-volume field-motion interactions that invalidate reference data in conventional approaches that use a single, static, fieldmap. The combination of accelerated acquisition with dynamic distortion correction yields volumes with very low distortion at repetition times similar to conventional echo-planar imaging. The method is applied to data acquired at 3 and 7 T and is shown to effectively correct image geometry. Furthermore, it is shown that dynamic distortion correction yields better temporal signal stability than correction using a static fieldmap in the presence of subject motion.

Original languageEnglish
Pages (from-to)1247-1254
Number of pages8
JournalMagnetic Resonance in Medicine
Issue number4
Publication statusPublished - Oct 2012
Externally publishedYes


  • Algorithms
  • Artifacts
  • Brain
  • Electron Spin Resonance Spectroscopy
  • Humans
  • Image Enhancement
  • Image Interpretation, Computer-Assisted
  • Reference Values
  • Reproducibility of Results
  • Sensitivity and Specificity
  • Signal Processing, Computer-Assisted

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