title: Optimizing three-dimensional time-of-flight MR angiography with variable repetition time.
abstract: OBJECTIVE
  To implement and evaluate a variable repetition time (TR) modification of three-dimensional (3D) time-of-flight (TOF) magnetic resonance (MR) angiography.
  
  
  METHODS
  Variable- and constant-TR 3D TOF MR angiography of the intracranial vasculature was performed in 20 healthy volunteers and 10 patients with known or suspected cerebrovascular disease. Total acquisition time was short and held constant for all studies. Frequency-selective fat saturation (FS) and magnetization transfer saturation (MTS) pulses were applied. The associated maximum-intensity projection (MIP) images were evaluated quantitatively for contrast-to-noise (C/N) and qualitatively for depiction of vessels that exhibit slow flow.
  
  
  RESULTS
  Variable-TR MIP images exhibited improved C/N and depiction of small peripheral vessels and venous structures when compared with constant-TR MIP images. These observations were consistent for all studies.
  
  
  CONCLUSIONS
  The variable-TR modification improved the depiction of intracranial vessels that exhibit slow flow.
authors.affiliation: Department of Radiology, Cleveland Clinic Foundation, OH 44106.
authors.forename: J A
authors.initials: JA
authors.lastname: Tkach
authors.forename: W
authors.initials: W
authors.lastname: Lin
authors.forename: J J
authors.initials: JJ
authors.lastname: Duda
authors.forename: E M
authors.initials: EM
authors.lastname: Haacke
authors.forename: T J
authors.initials: TJ
authors.lastname: Masaryk
mesh_terms: D000328:Adult; D002536:Cerebral Arteries / Q000473:pathology; D002560:Cerebrovascular Circulation; D002561:Cerebrovascular Disorders / Q000175:diagnosis / Q000503:physiopathology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008875:Middle Aged