title: PC HYPR flow: a technique for rapid imaging of contrast dynamics.
abstract: OBJECTIVE
  To improve spatial and temporal resolution and signal-to-noise ratio (SNR) in three-dimensional (3D) radial contrast-enhanced (CE) time-resolved MR angiography by means of a novel hybrid phase contrast (PC) and CE MRA acquisition and HYPR reconstruction (PC HYPR Flow).
  
  
  METHODS
  PC HYPR Flow consists of a CE exam immediately followed by a PC scan used to constrain the HYPR reconstruction of the time series. Temporal resolution of the new method was studied in computer simulations. The feasibility of the new technique was studied in healthy subjects and patients with brain arteriovenous malformations and in a canine model of aneurysms.
  
  
  RESULTS
  Simulations demonstrated preservation of contrast agent dynamics in proximal vessels, showing better performance than peer methods for acceleration up to 20 in 2D. In vivo, PC HYPR Flow yielded 3D time series with frame rate of 0.5 s and significantly outperformed two peer methods by means of a major increase in spatial resolution (0.8 x 0.8 x 0.8 mm(3)) and arterial/venous ratio, while maintaining necessary temporal waveform fidelity and high SNR.
  
  
  CONCLUSIONS
  This initial study indicates that PC HYPR Flow simultaneously provides 3D isotropic sub-millimeter spatial resolution, sub-second temporal reconstruction windows and high SNR level, which may benefit a wide range of CE MRA applications.
authors.affiliation: Department of Medical Physics, University of Wisconsin, Madison, WI, USA. velikina@wisc.edu
authors.forename: Julia V
authors.initials: JV
authors.lastname: Velikina
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Johnson
authors.forename: Yijing
authors.initials: Y
authors.lastname: Wu
authors.forename: Alexey A
authors.initials: AA
authors.lastname: Samsonov
authors.forename: Patrick
authors.initials: P
authors.lastname: Turski
authors.forename: Charles A
authors.initials: CA
authors.lastname: Mistretta
mesh_terms: D000465:Algorithms; D001808:Blood Vessels / Q000033:anatomy & histology*; D003198:Computer Simulation; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008955:Models, Cardiovascular; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity