title: Shared velocity encoding: a method to improve the temporal resolution of phase-contrast velocity measurements.
abstract: Phase-contrast magnetic resonance imaging (PC-MRI) is used routinely to measure fluid and tissue velocity with a variety of clinical applications. Phase-contrast magnetic resonance imaging methods require acquisition of additional data to enable phase difference reconstruction, making real-time imaging problematic. Shared Velocity Encoding (SVE), a method devised to improve the effective temporal resolution of phase-contrast magnetic resonance imaging, was implemented in a real-time pulse sequence with segmented echo planar readout. The effect of SVE on peak velocity measurement was investigated in computer simulation, and peak velocities and total flow were measured in a flow phantom and in volunteers and compared with a conventional ECG-triggered, segmented k-space phase-contrast sequence as a reference standard. Computer simulation showed a 36% reduction in peak velocity error from 8.8 to 5.6% with SVE. A similar reduction of 40% in peak velocity error was shown in a pulsatile flow phantom. In the phantom and volunteers, volume flow did not differ significantly when measured with or without SVE. Peak velocity measurements made in the volunteers using SVE showed a higher concordance correlation (0.96) with the reference standard than non-SVE (0.87). The improvement in effective temporal resolution with SVE reconstruction has a positive impact on the precision and accuracy of real-time phase-contrast magnetic resonance imaging peak velocity measurements.
authors.affiliation: Department of Biomedical Engineering, The Ohio State University, Columbus, Ohio, USA.
authors.forename: Hung-Yu
authors.initials: HY
authors.lastname: Lin
authors.forename: Jacob A
authors.initials: JA
authors.lastname: Bender
authors.forename: Yu
authors.initials: Y
authors.lastname: Ding
authors.forename: Yiu-Cho
authors.initials: YC
authors.lastname: Chung
authors.forename: Alice M
authors.initials: AM
authors.lastname: Hinton
authors.forename: Michael L
authors.initials: ML
authors.lastname: Pennell
authors.forename: Kevin K
authors.initials: KK
authors.lastname: Whitehead
authors.forename: Subha V
authors.initials: SV
authors.lastname: Raman
authors.forename: Orlando P
authors.initials: OP
authors.lastname: Simonetti
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology; D003326:Coronary Circulation / Q000502:physiology*; D003331:Coronary Vessels / Q000033:anatomy & histology* / Q000502:physiology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D018810:Magnetic Resonance Angiography / Q000379:methods*; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D008297:Male; D008875:Middle Aged; D055414:Myocardial Perfusion Imaging / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D055815:Young Adult