title: PC VIPR: a high-speed 3D phase-contrast method for flow quantification and high-resolution angiography.
abstract: OBJECTIVE
  Three-dimensional phase-contrast (3DPC) is limited by long imaging times, limited coverage, flow artifacts, and the need to perform multiple additional 2D examinations (2DPC) to measure flow. A highly undersampled 3D radial acquisition (isotropic-voxel radial projection imaging [PCVIPR]) makes it possible to increase the product of volume coverage and spatial resolution by a factor of 30 for the same imaging time as conventional Cartesian 3DPC. This provides anatomic information over a large volume with high isotropic resolution and permits retrospective measurement of average flow rates throughout the volume.
  
  
  METHODS
  PCVIPR acquires a reference and three flow-encoded acquisitions for each VIPR projection. Complex difference images were formed by combining information from all flow directions. Following retrospective definition of planes perpendicular to selected vessels, volume flow rates were determined by using phase-difference information. The accuracy of average flow measurement was investigated in a phantom and in six volunteers. Anatomic PCVIPR images acquired in three patients and three volunteers by using a 384(3) matrix were compared with conventional Cartesian 3DPC.
  
  
  RESULTS
  The flow validation produced R2 = 0.99 in vitro and R2 = 0.97 in vivo. PCVIPR produced minimal streak and pulsatile flow artifacts. PCVIPR produced far higher resolution and volume coverage in comparable imaging times. The highest acceleration factors relative to 3DPC were achieved by using gadolinium-contrast material. Ultimately, acceleration factors are limited by signal-to-noise ratio.
  
  
  CONCLUSIONS
  PCVIPR rapidly provides isotropic high-resolution angiographic images and permits retrospective measurement of average flow rate throughout the volume without the need to prescribe multiple 2D acquisition planes.
authors.affiliation: Department of Medical Physics, University of Wisconsin--Madison, Clinical Science Center, Madison, WI 53792-3252, USA.
authors.forename: Tianliang
authors.initials: T
authors.lastname: Gu
authors.forename: Frank R
authors.initials: FR
authors.lastname: Korosec
authors.forename: Walter F
authors.initials: WF
authors.lastname: Block
authors.forename: Sean B
authors.initials: SB
authors.lastname: Fain
authors.forename: Quill
authors.initials: Q
authors.lastname: Turk
authors.forename: Darren
authors.initials: D
authors.lastname: Lum
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhou
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Grist
authors.forename: Victor
authors.initials: V
authors.lastname: Haughton
authors.forename: Charles A
authors.initials: CA
authors.lastname: Mistretta
mesh_terms: D000328:Adult; D000792:Angiography / Q000379:methods*; D001488:Basilar Artery / Q000000981:diagnostic imaging*; D002536:Cerebral Arteries / Q000000981:diagnostic imaging*; D006801:Humans; D021621:Imaging, Three-Dimensional