title: The need for phase-encoding flow compensation in high-resolution intracranial magnetic resonance angiography.
abstract: OBJECTIVE
  To demonstrate that the time delay between phase and frequency encoding and the presence of pulsatile blood flow in high-resolution time-of-flight (TOF) imaging of the intracranial arteries (especially near the circle of Willis) can distort the appearance of blood vessels and result in a cross-hatch-appearing artifact in surrounding tissue.
  
  
  METHODS
  Two techniques to reduce the artifact, tri-directional flow compensation (3DFC) and elliptical-centric (EC) phase-encoding order, are investigated in five volunteer studies.
  
  
  RESULTS
  3DFC eliminates the pulsation-related artifacts and the vessel distortion. A residual amplitude variation artifact is observed. EC phase encoding nearly eliminates the pulsatile motion-related artifact, but it does not eliminate vessel distortion.
  
  
  CONCLUSIONS
  The combination of 3DFC and EC phase encoding appears to provide the greatest artifact reduction in the five volunteer studies performed.
authors.affiliation: Department of Radiology, University of Utah, Salt Lake City 84108, USA. parker@doug.med.utah.edu
authors.forename: Dennis L
authors.initials: DL
authors.lastname: Parker
authors.forename: K Craig
authors.initials: KC
authors.lastname: Goodrich
authors.forename: John A
authors.initials: JA
authors.lastname: Roberts
authors.forename: Brian E
authors.initials: BE
authors.lastname: Chapman
authors.forename: Eun-Kee
authors.initials: EK
authors.lastname: Jeong
authors.forename: Seong-Eun
authors.initials: SE
authors.lastname: Kim
authors.forename: Jay S
authors.initials: JS
authors.lastname: Tsuruda
authors.forename: Gregory L
authors.initials: GL
authors.lastname: Katzman
mesh_terms: D000328:Adult; D002560:Cerebrovascular Circulation; D018056:Hemorheology; D006801:Humans; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008875:Middle Aged; D013997:Time Factors