title: MR flow measurements for assessment of the pulmonary, systemic and bronchosystemic circulation: impact of different ECG gating methods and breathing schema.
abstract: OBJECTIVE
  Different ECG gating techniques are available for MR phase-contrast (PC) flow measurements. Until now no study has reported the impact of different ECG gating techniques on quantitative flow parameters. The goal was to evaluate the impact of the gating method and the breathing schema on the pulmonary, systemic and bronchosystemic circulation.
  
  
  METHODS
  Twenty volunteers were examined (1.5 T) with free breathing phase-contrast flow (PC-flow) measurements with prospective (free-prospective) and retrospective (free-retrospective) ECG gating. Additionally, expiratory breath-hold retrospective ECG gated measurements (bh-retrospective) were performed. Blood flow per minute; peak velocity and time to peak velocity were compared. The clinically important difference between the systemic and pulmonary circulation (bronchosystemic shunt) was calculated.
  
  
  RESULTS
  Blood flow per minute was lowest for free-prospective (6 l/min, pulmonary trunc) and highest for bh-retrospective measurements (6.9 l/min, pulmonary trunc). No clinically significant difference in peak velocity was assessed (82-83 cm/s pulmonary trunc, 109-113 cm/s aorta). Time to peak velocity was shorter for retro-gated free-retrospective and bh-retrospective than for pro-gated free-prospective. The difference between systemic and pulmonary measurements was least for the free-retrospective technique.
  
  
  CONCLUSIONS
  The type of gating has a significant impact on flow measurements. Therefore, it is important to use the same ECG gating method, especially for follow-up examinations. Retrospective ECG gated free breathing measurements allow for the most precise assessment of the bronchosystemic blood flow and should be used in clinical routine.
authors.affiliation: Department of Pediatric Radiology, Children's Hospital University Heidelberg, Im Neuenheimer Feld 153, 69120 Heidelberg, Germany. ley@gmx.net
authors.forename: Sebastian
authors.initials: S
authors.lastname: Ley
authors.forename: Julia
authors.initials: J
authors.lastname: Ley-Zaporozhan
authors.forename: Karl-Friedrich
authors.initials: KF
authors.lastname: Kreitner
authors.forename: Svitlana
authors.initials: S
authors.lastname: Iliyushenko
authors.forename: Michael
authors.initials: M
authors.lastname: Puderbach
authors.forename: Waldemar
authors.initials: W
authors.lastname: Hosch
authors.forename: Heiner
authors.initials: H
authors.lastname: Wenz
authors.forename: Jens-Peter
authors.initials: JP
authors.lastname: Schenk
authors.forename: Hans-Ulrich
authors.initials: HU
authors.lastname: Kauczor
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D011652:Pulmonary Circulation / Q000502:physiology*; D015203:Reproducibility of Results; D015656:Respiratory Mechanics; D012212:Rheology / Q000379:methods*; D012680:Sensitivity and Specificity