title: Flow volume and shunt quantification in pediatric congenital heart disease by real-time magnetic resonance velocity mapping: a validation study.
abstract: BACKGROUND
  Flow quantification in real time by phase-contrast MRI (PC-MRI) may provide unique hemodynamic information in congenital heart disease, but available techniques have important limitations. We sought to validate a novel real-time magnetic resonance flow sequence in children.
  
  
  RESULTS
  In 14 pediatric patients (mean age 5.2+/-2.0 years) with cardiac left-to-right shunt, pulmonary (Q(p)) and aortic (Q(s)) flow rates were determined by nontriggered free-breathing real-time PC-MRI with single-shot echo-planar imaging combined with sensitivity encoding, which yielded 25 phase images per second at 2.7x2.7-mm in-plane resolution (field of view 30x34 cm2). Over a 9.5-second period that included 2 to 5 respiratory cycles, 16.6+/-2.6 subsequent stroke volumes (range 13 to 22) were acquired in each vessel. Results were compared with conventional retrospectively ECG-gated PC-MRI. Mean Q(p)/Q(s) by conventional PC-MRI was 1.91+/-0.64, and it was 1.94+/-0.68 (mean+/-SD) by real-time PC-MRI. For blood flow rate through pulmonary artery and aorta, we found differences of 2% to 3% (Bland-Altman analysis), with lower limits of agreement of -11% to -13% (mean-2 SD) and upper limits of 18% to 19% (mean+2 SD), which demonstrated good agreement between both methods. Mean difference for Q(p)/Q(s) was 1%, with limits of agreement ranging between -18% and 22% (mean+/-2 SD). High repeatability but some flow overestimation was observed in vitro (pulsatile flow phantom) with real-time PC-MRI, whereas conventional PC-MRI was accurate. Beat-to-beat stroke-volume variation was 6.1+/-2.3% in vivo and 3.7+/-0.3% in vitro.
  
  
  CONCLUSIONS
  Beat-to-beat quantification of pulmonary and aortic flows and hence left-to-right shunt within a few seconds is reliable by nontriggered real-time PC-MRI with echo-planar imaging and sensitivity encoding. Good spatial/temporal resolution and a large field of view may render the sequence valuable for multiple applications in congenital heart disease.
authors.affiliation: Clinic for Congenital Heart Disease and Institute for Magnetic Resonance Imaging, Heart- and Diabetescenter Northrhine-Westfalia, Ruhr-University of Bochum, Germany.
authors.forename: Hermann
authors.initials: H
authors.lastname: Körperich
authors.forename: Jürgen
authors.initials: J
authors.lastname: Gieseke
authors.forename: Peter
authors.initials: P
authors.lastname: Barth
authors.forename: Romhild
authors.initials: R
authors.lastname: Hoogeveen
authors.forename: Hermann
authors.initials: H
authors.lastname: Esdorn
authors.forename: Andreas
authors.initials: A
authors.lastname: Peterschröder
authors.forename: Hans
authors.initials: H
authors.lastname: Meyer
authors.forename: Philipp
authors.initials: P
authors.lastname: Beerbaum
mesh_terms: D001775:Blood Circulation; D001783:Blood Flow Velocity; D002648:Child; D002675:Child, Preschool; D003326:Coronary Circulation; D017352:Echo-Planar Imaging / Q000379:methods*; D005260:Female; D006330:Heart Defects, Congenital / Q000175:diagnosis*; D006801:Humans; D007223:Infant; D008297:Male; D015588:Observer Variation; D015203:Reproducibility of Results; D013318:Stroke Volume