title: Retrospective motion compensation using variable-density spiral trajectories.
abstract: OBJECTIVE
  To develop a method of retrospectively correcting for motion artifacts using a variable-density spiral (VDS) trajectory.
  
  
  METHODS
  Each VDS interleaf was designed to adequately sample the same center region of k-space. This central overlapping region can then be used to measure rigid body motion between the acquisition of each VDS interleaf. By applying appropriate phase shifts and rotations of the k-space data, rigid body motion artifacts can be removed, resulting in images with less motion corruption.
  
  
  RESULTS
  Both phantom and volunteer experiments are shown, demonstrating the technique's ability to further reduce artifacts in images acquired with an already motion-resistant acquisition trajectory. Registration accuracy is highly dependent on the trajectory design parameters. This space was explored to find an optimal design of VDS trajectories for motion compensation.
  
  
  CONCLUSIONS
  Using appropriately designed VDS trajectories, residual motion artifacts can be significantly reduced by retrospectively correcting for in-plane rigid body motion. An overlapping region of approximately 8% of the central region of k-space and approximately 70 interleaves were found to be near-optimal parameters for retrospective correction using VDS trajectories.
authors.affiliation: Department of Medical Biophysics, University of Toronto, Sunnybrook and Women's College Health Sciences Center, Toronto, Canada.
authors.forename: General
authors.initials: G
authors.lastname: Leung
authors.forename: Donald B
authors.initials: DB
authors.lastname: Plewes
mesh_terms: D016477:Artifacts; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009038:Motion; D019047:Phantoms, Imaging