title: 3D TOF MRA of intracranial aneurysms at 1.5 T and 3 T: influence of matrix, parallel imaging, and acquisition time on image quality - a vascular phantom study.
abstract: OBJECTIVE
  A 3-T magnetic resonance imaging system provides a better signal-to-noise ratio and inflow effect than 1.5 T in three-dimensional time-of-flight (3D TOF) magnetic resonance angiography (MRA). The purpose of this study is to analyze the influence of matrix, parallel imaging, and acquisition time on image quality of 3D TOF MRA at 1.5 and 3 T, and to illustrate whether the combination of larger matrixes with parallel imaging technique is feasible, by evaluating the visualization of simulated intracranial aneurysms and aneurysmal blebs using a vascular phantom with pulsatile flow.
  
  
  METHODS
  An anthropomorphic vascular phantom was designed to simulate the various intracranial aneurysms with aneurysmal bleb. The vascular phantom was connected to an electromagnetic flow pump with pulsatile flow, and we obtained 1.5- and 3-T MRAs altering the parameters of 3D TOF sequences, including acquisition time. Two radiologists evaluated the depiction of simulated aneurysms and aneurysmal blebs.
  
  
  RESULTS
  The aneurysmal blebs were not sufficiently visualized on the high-spatial resolution 1.5-T MRA (matrix size of 384 x 256 or 512 x 256), even with longer acquisition time (9 or 18 min). At 3 T with acquisition time of 4.5 min using parallel imaging technique, however, the depiction of aneurysmal blebs was significantly better for the high-spatial resolution sequence than for the standard resolution sequence. For the high-spatial resolution sequence, the longer acquisition times did not improve the depiction of aneurysmal blebs in comparison with 4.5 min at 3 T.
  
  
  CONCLUSIONS
  For 3D TOF MRA, the combination of the large matrix with parallel imaging technique is feasible at 3 T, but not at 1.5 T.
authors.affiliation: Department of Course of Radiological Sciences, Kumamoto University School of Health Sciences, Kumamoto University School of Medicine, 4-24-1 Kuhonji, Kumamoto 862-0976, Japan. Hiai@hs.kunamoto-u.ac.jp
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Hiai
authors.forename: Shingo
authors.initials: S
authors.lastname: Kakeda
authors.forename: Toru
authors.initials: T
authors.lastname: Sato
authors.forename: Norihiro
authors.initials: N
authors.lastname: Ohnari
authors.forename: Junji
authors.initials: J
authors.lastname: Moriya
authors.forename: Mika
authors.initials: M
authors.lastname: Kitajima
authors.forename: Toshinori
authors.initials: T
authors.lastname: Hirai
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Yamashita
authors.forename: Yukunori
authors.initials: Y
authors.lastname: Korogi
mesh_terms: D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D002532:Intracranial Aneurysm / Q000175:diagnosis*; D018810:Magnetic Resonance Angiography / Q000379:methods*; D019047:Phantoms, Imaging; D011673:Pulsatile Flow; D015203:Reproducibility of Results; D018709:Statistics, Nonparametric