title: CE-MRA of the lower extremities using HYPR stack-of-stars.
abstract: OBJECTIVE
  To investigate the properties of HYPR (HighlY constrained back PRojection) processing-the temporal fidelity and the improvements of spatial/temporal resolution-for contrast-enhanced MR angiography in a pilot study of the lower extremities in healthy volunteers.
  
  
  METHODS
  HYPR processing with a radial three-dimensional (3D) stack-of-stars acquisition was investigated for contrast-enhanced MR angiography of the lower extremities in 15 healthy volunteers. HYPR images were compared with control images acquired using a fast, multiphase, 2D Cartesian method to verify the temporal fidelity of HYPR. HYPR protocols were developed for achieving either a high frame update rate or a minimal slice thickness by adjusting the acquisition parameters. HYPR images were compared with images obtained using 3D TRICKS, a widely used protocol in dynamic 3D MRA.
  
  
  RESULTS
  HYPR images showed good temporal agreement with 2D control images. In comparison with TRICKS, HYPR stack-of-stars demonstrated higher spatial and temporal resolution. High radial undersampling factors for each time frame were permitted, typically approximately 50 to 100 compared with fully sampled radial imaging.
  
  
  CONCLUSIONS
  In this feasibility study, HYPR processing has been demonstrated to improve the spatial or temporal resolution in peripheral CE-MRA.
authors.affiliation: Department of Electrical and Computer Engineering, University of Wisconsin, Madison, Wisconsin, USA.
authors.forename: Yan
authors.initials: Y
authors.lastname: Wu
authors.forename: Frank R
authors.initials: FR
authors.lastname: Korosec
authors.forename: Charles A
authors.initials: CA
authors.lastname: Mistretta
authors.forename: Oliver
authors.initials: O
authors.lastname: Wieben
mesh_terms: D016477:Artifacts; D003287:Contrast Media; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007866:Leg / Q000098:blood supply*; D018810:Magnetic Resonance Angiography / Q000379:methods*; D010865:Pilot Projects
chemical_list: D003287:Contrast Media