title: Time-resolved 3D MR velocity mapping at 3T: improved navigator-gated assessment of vascular anatomy and blood flow.
abstract: OBJECTIVE
  To evaluate an improved image acquisition and data-processing strategy for assessing aortic vascular geometry and 3D blood flow at 3T.
  
  
  METHODS
  In a study with five normal volunteers and seven patients with known aortic pathology, prospectively ECG-gated cine three-dimensional (3D) MR velocity mapping with improved navigator gating, real-time adaptive k-space ordering and dynamic adjustment of the navigator acceptance criteria was performed. In addition to morphological information and three-directional blood flow velocities, phase-contrast (PC)-MRA images were derived from the same data set, which permitted 3D isosurface rendering of vascular boundaries in combination with visualization of blood-flow patterns.
  
  
  RESULTS
  Analysis of navigator performance and image quality revealed improved scan efficiencies of 63.6%+/-10.5% and temporal resolution (<50 msec) compared to previous implementations. Semiquantitative evaluation of image quality by three independent observers demonstrated excellent general image appearance with moderate blurring and minor ghosting artifacts. Results from volunteer and patient examinations illustrate the potential of the improved image acquisition and data-processing strategy for identifying normal and pathological blood-flow characteristics.
  
  
  CONCLUSIONS
  Navigator-gated time-resolved 3D MR velocity mapping at 3T in combination with advanced data processing is a powerful tool for performing detailed assessments of global and local blood-flow characteristics in the aorta to describe or exclude vascular alterations.
authors.affiliation: Department of Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany. michael.markl@uniklinik-freiburg.de
authors.forename: Michael
authors.initials: M
authors.lastname: Markl
authors.forename: Andreas
authors.initials: A
authors.lastname: Harloff
authors.forename: Thorsten A
authors.initials: TA
authors.lastname: Bley
authors.forename: Maxim
authors.initials: M
authors.lastname: Zaitsev
authors.forename: Bernd
authors.initials: B
authors.lastname: Jung
authors.forename: Ernst
authors.initials: E
authors.lastname: Weigang
authors.forename: Mathias
authors.initials: M
authors.lastname: Langer
authors.forename: Jürgen
authors.initials: J
authors.lastname: Hennig
authors.forename: Alex
authors.initials: A
authors.lastname: Frydrychowicz
mesh_terms: D000328:Adult; D000368:Aged; D001012:Aorta, Abdominal / Q000033:anatomy & histology / Q000473:pathology / Q000502:physiology*; D001013:Aorta, Thoracic / Q000033:anatomy & histology / Q000473:pathology / Q000502:physiology*; D001018:Aortic Diseases / Q000473:pathology / Q000503:physiopathology; D001783:Blood Flow Velocity / Q000502:physiology; D004562:Electrocardiography; D005260:Female; D006801:Humans; D007089:Image Enhancement; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged