title: Convex gradient optimization for increased spatiotemporal resolution and improved accuracy in phase contrast MRI.
abstract: OBJECTIVE
  To evaluate convex gradient optimization (CVX) for increased spatiotemporal resolution and improved accuracy for phase-contrast MRI (PC-MRI).
  
  
  METHODS
  A conventional flow-compensated and flow-encoded (FCFE) PC-MRI sequence was compared with a CVX PC-MRI sequence using numerical simulations, flow phantom experiments, and in vivo experiments. Flow measurements within the ascending aorta, main pulmonary artery, and right/left pulmonary arteries of normal volunteers (N = 10) were acquired at 3T and analyzed using a conventional FCFE sequence and a CVX sequence with either higher spatial resolution or higher temporal resolution. All sequences mitigated chemical shift-induced phase errors and used equivalent breath-hold durations.
  
  
  RESULTS
  Chemical shift-optimized PC-MRI has increased sequence efficiency when using CVX, which can provide either higher spatial or higher temporal resolution compared with conventional FCFE PC-MRI. Numerical simulations, flow phantom experiments, and in vivo experiments indicate that CVX measurements of total flow and peak velocity are increased and more accurate when compared with FCFE.
  
  
  CONCLUSIONS
  CVX PC-MRI increases sequence efficiency while reducing chemical shift-induced phase errors. This can be used to provide either higher spatial or higher temporal resolution than conventional chemical shift-mitigated PC-MRI methods to provide more accurate measurements of blood flow and peak velocity.
authors.affiliation: Department of Radiological Sciences, University of California, Los Angeles, Los Angeles, California, USA; Biomedical Physics Interdepartmental Program, University of California, Los Angeles, Los Angeles, California, USA.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Middione
authors.forename: Holden H
authors.initials: HH
authors.lastname: Wu
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Ennis
mesh_terms: D000328:Adult; D000465:Algorithms; D001011:Aorta / Q000033:anatomy & histology / Q000502:physiology*; D001783:Blood Flow Velocity / Q000502:physiology*; D003198:Computer Simulation; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D008955:Models, Cardiovascular; D011651:Pulmonary Artery / Q000033:anatomy & histology / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D062211:Spatio-Temporal Analysis
keywords: convex gradient optimization; flow quantification; phase contrast MRI