title: Three- and four-dimensional freehand fetal echocardiography: a feasibility study using a hand-held Doppler probe for cardiac gating.
abstract: OBJECTIVE
  To evaluate the clinical feasibility of the signal from a hand-held Doppler probe as a real-time tracking signal for dynamic three-dimensional (3D) (so-called four-dimensional (4D)) fetal echocardiography in a random patient cohort.
  
  
  METHODS
  Seventy fetuses, with and without congenital heart disease, at various gestational ages (mean, 25 weeks; range, 18-38 weeks) were investigated using freehand 3D echocardiography. Time gating was achieved concurrently by obtaining a Doppler signal of the fetal heart without further signal averaging. In 10 fetuses, Doppler gating was compared to cardiotocogram (CTG)-gated 3D echo using signal averaging. Gray-scale and color Doppler dynamic 3D displays and multiplanar views were assessed according to their ability to accurately depict cardiac gating and cardiac morphology.
  
  
  RESULTS
  In 68/70 fetuses, valid Doppler-based trigger signals were obtained. Correct cardiac gating was achieved in 231/275 (84%) 4D datasets. Doppler tracing of the fetal heart allowed beat-to-beat triggering without the necessity for signal averaging. Doppler gating detected rapid changes in the fetal heart rate more reliably than CTG gating, but was more sensitive to acoustic interference between the gating and echo-transducer when color-coded Doppler imaging was used. Image quality was highly dependent on random motion and the acoustic window. A total of 171/231 (74%) correctly gated datasets successfully demonstrated clinically useful 4D images of the fetal heart. The reconstruction of 3D and multiplanar views provided additional views not obtainable by two-dimensional imaging.
  
  
  CONCLUSIONS
  These results show that a hand-held Doppler probe can be used as a reliable online gating source for 4D fetal echocardiography.
authors.affiliation: Division of Pediatric Cardiology, Children's Hospital, University of Bonn, Bonn, Germany. Ulrike.Herberg@ukb.uni-bonn.de
authors.forename: U
authors.initials: U
authors.lastname: Herberg
authors.forename: H
authors.initials: H
authors.lastname: Goldberg
authors.forename: J
authors.initials: J
authors.lastname: Breuer
mesh_terms: D000328:Adult; D015148:Cardiotocography / Q000379:methods; D015331:Cohort Studies; D015150:Echocardiography, Doppler / Q000295:instrumentation / Q000379:methods*; D019561:Echocardiography, Four-Dimensional / Q000295:instrumentation / Q000379:methods; D019560:Echocardiography, Three-Dimensional / Q000295:instrumentation / Q000379:methods*; D005240:Feasibility Studies; D005260:Female; D005318:Fetal Heart / Q000000981:diagnostic imaging / Q000503:physiopathology; D006330:Heart Defects, Congenital / Q000000981:diagnostic imaging / Q000503:physiopathology; D006340:Heart Rate, Fetal / Q000502:physiology*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D011247:Pregnancy; D015203:Reproducibility of Results; D016216:Ultrasonography, Prenatal / Q000295:instrumentation / Q000379:methods