Prevention of motion-induced signal loss in diffusion-weighted echo-planar imaging by dynamic restoration of gradient moments

Magn Reson Med. 2014 Jun;71(6):2006-13. doi: 10.1002/mrm.24857. Epub 2013 Jul 2.


Purpose: Head motion is a significant problem in diffusion-weighted imaging as it may cause signal attenuation due to residual dephasing during strong diffusion encoding gradients even in single-shot acquisitions. Here, we present a new real-time method to prevent motion-induced signal loss in DWI of the brain.

Methods: The method requires a fast motion tracking system (optical in the current implementation). Two alterations were made to a standard diffusion-weighted echo-planar imaging sequence: first, real-time motion correction ensures that slices are correctly aligned relative to the moving brain. Second, the tracking data are used to calculate the motion-induced gradient moment imbalance which occurs during the diffusion encoding periods, and a brief gradient blip is inserted immediately prior to the signal readout to restore the gradient moment balance.

Results: Phantom experiments show that the direction as well as magnitude of the gradient moment imbalance affects the characteristics of unwanted signal attenuation. In human subjects, the addition of a moment-restoring blip prevented signal loss and improved the reproducibility and reliability of diffusion tensor measures even in the presence of substantial head movements.

Conclusion: The method presented can improve robustness for clinical routine scanning in populations that are prone to head movements, such as children and uncooperative adult patients.

Keywords: diffusion weighted imaging; gradient moment restoration; real-time motion tracking; signal loss.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Diffusion Magnetic Resonance Imaging / methods*
  • Echo-Planar Imaging / methods
  • Head Movements*
  • Healthy Volunteers
  • Humans
  • Image Processing, Computer-Assisted / methods*
  • Motion
  • Phantoms, Imaging
  • Reproducibility of Results
  • Signal Processing, Computer-Assisted