title: Real-time interactive duplex MR measurements: application in neurovascular imaging.
abstract: OBJECTIVE
  Real-time interactive duplex MR imaging is a new phase-contrast MR imaging technique that enables the quantification and display of flow velocities in real time without the need for cardiac gating. We investigated the feasibility and reliability of the technique to assess hemodynamic information both in vitro and in vivo in the carotid arteries and in the venous sinuses.
  
  
  METHODS
  Real-time interactive duplex MR measurements (TR/TE, 53/27; flip angle, 90 degrees; encoding velocity, 100 or 150 cm/sec) were performed in vitro with a steady-flow phantom and in 10 healthy volunteers in whom common and internal carotid artery velocities were measured. In eight volunteers, velocity measurements were also performed in the superior sagittal sinus during both normal breathing and hyperventilation. Time-velocity plots were analyzed qualitatively and quantitatively and compared with findings from conventional segmented k-space phase-contrast MR imaging and Doppler sonography.
  
  
  RESULTS
  Velocity determinations for real-time duplex MR and conventional phase-contrast MR imaging showed an in vitro correlation of 0.99 and an in vivo correlation of 0.83 (carotid arteries) and 0.76 (venous sinus). Velocity measurements in the carotid arteries with real-time MR imaging were significantly lower than those obtained with conventional phase-contrast MR (averaged, 7.8%; p = 0.003) or sonography (23.7%, p < 0.001), likely because of volume averaging. Small but significant velocity changes occurring in the venous sinus during hyperventilation were reliably identified with both MR techniques.
  
  
  CONCLUSIONS
  Real-time interactive duplex MR imaging can be effectively applied in neurovascular imaging to obtain hemodynamic information.
authors.affiliation: Department of Radiology, New York University Medical Center, 530 First Ave., HCC Basement-MRI, New York, NY 10016, USA.
authors.forename: S G
authors.initials: SG
authors.lastname: Wetzel
authors.forename: V S
authors.initials: VS
authors.lastname: Lee
authors.forename: A G
authors.initials: AG
authors.lastname: Tan
authors.forename: O
authors.initials: O
authors.lastname: Heid
authors.forename: S
authors.initials: S
authors.lastname: Cha
authors.forename: G
authors.initials: G
authors.lastname: Johnson
authors.forename: N M
authors.initials: NM
authors.lastname: Rofsky
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001783:Blood Flow Velocity / Q000502:physiology; D002339:Carotid Arteries / Q000033:anatomy & histology*; D003392:Cranial Sinuses / Q000033:anatomy & histology*; D005260:Female; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D019047:Phantoms, Imaging; D012016:Reference Values; D012680:Sensitivity and Specificity