title: Blood flow of ophthalmic artery in healthy individuals determined by phase-contrast magnetic resonance imaging.
abstract: OBJECTIVE
  Recent development of magnetic resonance imaging (MRI) offers new possibilities to assess ocular blood flow. This prospective study evaluates the feasibility of phase-contrast MRI (PCMRI) to measure flow rate in the ophthalmic artery (OA) and establish reference values in healthy young (HY) and elderly (HE) subjects.
  
  
  METHODS
  Fifty HY subjects (28 females, 21-30 years of age) and 44 HE (23 females, 64-80 years of age) were scanned on a 3-Tesla MR system. The PCMRI sequence had a spatial resolution of 0.35 mm per pixel, with the measurement plan placed perpendicularly to the OA. Mean flow rate (Qmean), resistive index (RI), and arterial volume pulsatility of OA (ΔVmax) were measured from the flow rate curve. Accuracy of PCMRI measures was investigated using a vessel-phantom mimicking the diameter and the flow rate range of the human OA.
  
  
  RESULTS
  Flow rate could be assessed in 97% of the OAs. Phantom investigations showed good agreement between the reference and PCMRI measurements with an error of <7%. No statistical difference was found in Qmean between HY and HE individuals (HY: mean ± SD = 10.37 ± 4.45 mL/min; HE: 10.81 ± 5.15 mL/min, P = 0.655). The mean of ΔVmax (HY: 18.70 ± 7.24 μL; HE: 26.27 ± 12.59 μL, P < 0.001) and RI (HY: 0.62 ± 0.08; HE: 0.67 ± 0.1, P = 0.012) were significantly different between HY and HE.
  
  
  CONCLUSIONS
  This study demonstrated that the flow rate of OA can be quantified using PCMRI. There was an age difference in the pulsatility parameters; however, the mean flow rate appeared independent of age. The primary difference in flow curves between HE and HY was in the relaxation phase of the systolic peak.
authors.affiliation: Department of Radiation Sciences, Umeå. khalid.ambarki@vll.se
authors.forename: Khalid
authors.initials: K
authors.lastname: Ambarki
authors.forename: Per
authors.initials: P
authors.lastname: Hallberg
authors.forename: Gauti
authors.initials: G
authors.lastname: Jóhannesson
authors.forename: Christina
authors.initials: C
authors.lastname: Lindén
authors.forename: Laleh
authors.initials: L
authors.lastname: Zarrinkoob
authors.forename: Anders
authors.initials: A
authors.lastname: Wåhlin
authors.forename: Richard
authors.initials: R
authors.lastname: Birgander
authors.forename: Jan
authors.initials: J
authors.lastname: Malm
authors.forename: Anders
authors.initials: A
authors.lastname: Eklund
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D005240:Feasibility Studies; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009880:Ophthalmic Artery / Q000502:physiology*; D011446:Prospective Studies; D012016:Reference Values; D012039:Regional Blood Flow / Q000502:physiology*; D055815:Young Adult