title: Determining exercise-induced blood flow reserve in lower extremities using phase contrast MRI.
abstract: OBJECTIVE
  To study the changes in limb blood flow during lower extremity exercise using phase contrast (PC) MRI in normal volunteers.
  
  
  METHODS
  Healthy volunteers performed plantar flexion exercise (<1 W) for four minutes. Flow velocity was measured using cardiac-gated, cine PC-MRI sequences (fast gradient recalled echo [GRE]; multishot echo planar imaging [EPI]) on a 3T scanner at the level of the superficial femoral artery (SFA): 1) preexercise; 2) immediately postexercise; 3) during three minutes recovery; and 4) postrecovery.
  
  
  RESULTS
  At rest there was a triphasic flow waveform in the SFA. During exercise it changed to a monophasic pattern with an increase in total flow; there were variable changes in vessel size and flow velocity. The waveform regained the triphasic pattern during recovery. The exercise-induced flow reserve (FR) was 167 +/- 90%.
  
  
  CONCLUSIONS
  PC-MRI demonstrates that the resting triphasic flow waveform transforms into a monophasic pattern with submaximal exercise and returns to baseline with recovery. This increase in the regional blood flow allows for measurement of exercise-induced FR in the SFA.
authors.affiliation: Department of Medicine, Division of Cardiovascular Disease, University of Alabama at Birmingham, Birmingham, Alabama, USA.
authors.forename: Hosakote M
authors.initials: HM
authors.lastname: Nagaraj
authors.forename: Amol
authors.initials: A
authors.lastname: Pednekar
authors.forename: Cecilia
authors.initials: C
authors.lastname: Corros
authors.forename: Himanshu
authors.initials: H
authors.lastname: Gupta
authors.forename: Steven G
authors.initials: SG
authors.lastname: Lloyd
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D035002:Lower Extremity / Q000098:blood supply*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male