Centering the projection reconstruction trajectory: Reducing gradient delay errors

Dana C. Peters, J. Andrew Derbyshire, Elliot R. McVeigh

Research output: Contribution to journalArticlepeer-review

109 Scopus citations


The projection reconstruction (PR) trajectory was investigated for the effect of gradient timing delays between the actual and requested start time of each physical gradient. Radial trajectories constructed with delayed gradients miss the center of k-space in an angularly dependent manner, causing effective echo times to vary with projection angle. The gradient timing delays were measured in phantoms, revealing delays on the x, y, and z gradients which differed by as much as 5 μsec. Using this one-time calibration measurement, the trajectories were corrected for gradient delays by addition of compensatory gradient areas to the prephasers of the logical x and y readout gradients. Effective projection-to-projection echo time variability was reduced to less than 1 μsec for all imaging orientations. Using corrected trajectories, artifacts were reduced in phantom images and in volunteer studies. This correction should potentiate greater clinical use of the PR trajectory.

Original languageEnglish (US)
Pages (from-to)1-6
Number of pages6
JournalMagnetic Resonance in Medicine
Issue number1
StatePublished - Jul 1 2003
Externally publishedYes


  • Compensation blips
  • Echo-planar imaging
  • Gradient delay
  • Gradient errors
  • Linear phase
  • Magnitude back projection
  • Projection reconstruction
  • Radial imaging
  • Reference scans

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging
  • Radiological and Ultrasound Technology


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