title: Visualization of hemodynamics in intracranial arteries using time-resolved three-dimensional phase-contrast MRI.
abstract: OBJECTIVE
  To visualize the hemodynamics of the intracranial arteries using time-resolved three-dimensional phase-contrast (PC)-MRI (4D-Flow).
  
  
  METHODS
  MR examinations were performed with a 1.5T MR unit on six healthy volunteers (22-50 years old, average = 30 years). 4D-Flow was based on a radiofrequency (RF)-spoiled gradient-echo sequence, and velocity encoding (VENC) was performed along all three spatial directions. Measurements were retrospectively gated to the electrocardiogram (ECG), and cine series of three-dimensional (3D) data sets were generated. The voxel size was 1 x 1 x 1 mm, and acquisition time was 30-40 minutes. 4D data sets were calculated into time-resolved images of 3D streamlines, 3D particle traces, and 2D velocity vector fields by means of flow visualization software.
  
  
  RESULTS
  We were able to see the 3D streamlines from the circle of Willis to the bilateral M2 segment of the middle cerebral arteries (MCAs). Time-resolved images of 3D particle traces also clearly demonstrated intracranial arterial flow dynamics. 2D velocity vector fields on the planes traversing the carotid siphon or the basilar tip were clearly visualized. These results were obtained in all six volunteers.
  
  
  CONCLUSIONS
  4D-Flow helped to elucidate the in vivo 3D hemodynamics of human intracranial arteries. This method may be a useful noninvasive means of analyzing the hemodynamics of intracranial arteries in vivo.
authors.affiliation: Department of Radiology, Hamamatsu University School of Medicine, Shizuoka, Japan. shuheiy@hama-med.ac.jp
authors.forename: Shuhei
authors.initials: S
authors.lastname: Yamashita
authors.forename: Haruo
authors.initials: H
authors.lastname: Isoda
authors.forename: Masaya
authors.initials: M
authors.lastname: Hirano
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Takeda
authors.forename: Shoichi
authors.initials: S
authors.lastname: Inagawa
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Takehara
authors.forename: Marcus T
authors.initials: MT
authors.lastname: Alley
authors.forename: Michael
authors.initials: M
authors.lastname: Markl
authors.forename: Norbert J
authors.initials: NJ
authors.lastname: Pelc
authors.forename: Harumi
authors.initials: H
authors.lastname: Sakahara
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity; D002536:Cerebral Arteries / Q000033:anatomy & histology*; D004562:Electrocardiography / Q000379:methods; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods*; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011673:Pulsatile Flow / Q000502:physiology; D012016:Reference Values; D013997:Time Factors