title: Accuracy of MR phase contrast velocity measurements for unsteady flow.
abstract: The accuracy of MR phase contrast (PC) velocity measurements for unsteady flow has been quantitatively assessed. Spatially resolved velocity fields were measured in a long straight tube using a gated PC technique, and the resulting MR PC velocity data were compared with velocities derived from the analytic Womersley solution to the Navier-Stokes equations governing fluid flow. The overall root-mean-square (rms) difference between the measured and analytic velocities was 1.6 cm s-1 for nominally sinusoidal flow waveforms with peak velocities ranging from 51.6 cm s-1 to 59.8 cm s-1. This rms difference corresponded to 7.5% of the mean fluid velocity, which is similar to the cited accuracy of approximately 5% for MR PC velocimetry for steady flows. Linear regression between the PC velocity measurements and the velocities obtained using the analytic expression was highly significant (r2 = 0.997) and yielded a slope of 0.998, close to the expected value of 1. We conclude that the gated MR PC velocity measurements in unsteady flow are accurate.
authors.affiliation: Department of Radiology, University of Western Ontario, London, Canada.
authors.forename: R
authors.initials: R
authors.lastname: Frayne
authors.forename: D A
authors.initials: DA
authors.lastname: Steinman
authors.forename: C R
authors.initials: CR
authors.lastname: Ethier
authors.forename: B K
authors.initials: BK
authors.lastname: Rutt
mesh_terms: D001783:Blood Flow Velocity; D018056:Hemorheology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D016014:Linear Models; D008279:Magnetic Resonance Imaging / Q000379:methods*; D019047:Phantoms, Imaging