A new design and rationale for 3D orthogonally oversampled k-space trajectories

James G. Pipe, Nicholas R. Zwart, Eric A. Aboussouan, Ryan K. Robison, Ajit Devaraj, Kenneth O. Johnson

Research output: Contribution to journalArticlepeer-review

63 Scopus citations


A novel center-out 3D trajectory for sampling magnetic resonance data is presented. The trajectory set is based on a single Fermat spiral waveform, which is substantially undersampled in the center of k-space. Multiple trajectories are combined in a "stacked cone" configuration to give very uniform sampling throughout a "hub," which is very efficient in terms of gradient performance and uniform trajectory spacing. The fermat looped, orthogonally encoded trajectories (FLORET) design produces less gradient-efficient trajectories near the poles, so multiple orthogonal hub designs are shown. These multihub designs oversample k-space twice with orthogonal trajectories, which gives unique properties but also doubles the minimum scan time for critical sampling of k-space. The trajectory is shown to be much more efficient than the conventional stack of cones trajectory, and has nearly the same signal-to-noise ratio efficiency (but twice the minimum scan time) as a stack of spirals trajectory. As a center-out trajectory, it provides a shorter minimum echo time than stack of spirals, and its spherical k-space coverage can dramatically reduce Gibbs ringing.

Original languageEnglish (US)
Pages (from-to)1303-1311
Number of pages9
JournalMagnetic Resonance in Medicine
Issue number5
StatePublished - Nov 2011


  • k-space trajectory
  • spiral MRI
  • undersampling

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging


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