title: Time-resolved three-dimensional phase-contrast MRI.
abstract: OBJECTIVE
  To demonstrate the feasibility of a four-dimensional phase contrast (PC) technique that permits spatial and temporal coverage of an entire three-dimensional volume, to quantitatively validate its accuracy against an established time resolved two-dimensional PC technique to explore advantages of the approach with regard to the four-dimensional nature of the data.
  
  
  METHODS
  Time-resolved, three-dimensional anatomical images were generated simultaneously with registered three-directional velocity vector fields. Improvements compared to prior methods include retrospectively gated and respiratory compensated image acquisition, interleaved flow encoding with freely selectable velocity encoding (venc) along each spatial direction, and flexible trade-off between temporal resolution and total acquisition time.
  
  
  RESULTS
  The implementation was validated against established two-dimensional PC techniques using a well-defined phantom, and successfully applied in volunteer and patient examinations. Human studies were performed after contrast administration in order to compensate for loss of in-flow enhancement in the four-dimensional approach.
  
  
  CONCLUSIONS
  Advantages of the four-dimensional approach include the complete spatial and temporal coverage of the cardiovascular region of interest and the ability to obtain high spatial resolution in all three dimensions with higher signal-to-noise ratio compared to two-dimensional methods at the same resolution. In addition, the four-dimensional nature of the data offers a variety of image processing options, such as magnitude and velocity multi-planar reformation, three-directional vector field plots, and velocity profiles mapped onto selected planes of interest.
authors.affiliation: Department of Radiology, Stanford University, Stanford, California 94304, USA. markl@s-word.stanford.edu
authors.forename: Michael
authors.initials: M
authors.lastname: Markl
authors.forename: Frandics P
authors.initials: FP
authors.lastname: Chan
authors.forename: Marcus T
authors.initials: MT
authors.lastname: Alley
authors.forename: Kris L
authors.initials: KL
authors.lastname: Wedding
authors.forename: Mary T
authors.initials: MT
authors.lastname: Draney
authors.forename: Chris J
authors.initials: CJ
authors.lastname: Elkins
authors.forename: David W
authors.initials: DW
authors.lastname: Parker
authors.forename: Ryan
authors.initials: R
authors.lastname: Wicker
authors.forename: Charles A
authors.initials: CA
authors.lastname: Taylor
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Herfkens
authors.forename: Norbert J
authors.initials: NJ
authors.lastname: Pelc
mesh_terms: D003287:Contrast Media; D003326:Coronary Circulation / Q000502:physiology*; D005240:Feasibility Studies; D019786:Gadolinium DTPA; D006801:Humans; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging / Q000379:methods*; D019047:Phantoms, Imaging
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA