title: Improved cardiovascular flow quantification with time-resolved volumetric phase-contrast MRI.
abstract: BACKGROUND
  Cardiovascular flow is commonly assessed with two-dimensional, phase-contrast MRI (2-D PC-MRI). However, scan prescription and acquisition over multiple planes is lengthy, often requires direct physician oversight and has inconsistent results. Time-resolved volumetric PC-MRI (4-D flow) may address these limitations.
  
  
  OBJECTIVE
  We assess the degree of agreement and internal consistency between 2-D and 4-D flow quantification in our clinical population.
  
  
  METHODS
  Software enabling flow calculation from 4-D flow was developed in Java. With IRB approval and HIPAA compliance, 18 consecutive patients without shunts were identified who underwent both (1) conventional 2-D PC-MRI of the aorta and main pulmonary artery and (2) 4-D flow imaging. Aortic and pulmonary flow rates were assessed with both techniques.
  
  
  RESULTS
  Both methods showed general agreement in flow rates (ρ: 0.87-0.90). Systemic and pulmonary arterial flow rates were well-correlated (ρ: 4-D 0.98-0.99, 2-D 0.93), but more closely matched with 4-D (P < 0.05, Brown-Forsythe). Pulmonary flow rates were lower than systemic rates for 2-D (P < 0.05, two-sample t-test). In a sub-analysis of patients without pulmonary or aortic regurgitation, 2-D showed improved correlation of flow rates while 4-D phase-contrast remained tightly correlated (ρ: 4-D 0.99-1.00, 2-D 0.99).
  
  
  CONCLUSIONS
  4-D PC-MRI demonstrates greater consistency than conventional 2-D PC-MRI for flow quantification.
authors.affiliation: Department of Radiology, 725 Welch Road, Stanford, CA 94305-5654, USA.
authors.forename: Albert
authors.initials: A
authors.lastname: Hsiao
authors.forename: Marcus T
authors.initials: MT
authors.lastname: Alley
authors.forename: Payam
authors.initials: P
authors.lastname: Massaband
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Herfkens
authors.forename: Frandics P
authors.initials: FP
authors.lastname: Chan
authors.forename: Shreyas S
authors.initials: SS
authors.lastname: Vasanawala
mesh_terms: D000293:Adolescent; D000328:Adult; D000465:Algorithms; D055424:Cardiac-Gated Imaging Techniques / Q000379:methods*; D002648:Child; D002675:Child, Preschool; D003326:Coronary Circulation; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D018810:Magnetic Resonance Angiography / Q000379:methods*; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D008297:Male; D011652:Pulmonary Circulation; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity