title: Coronary MR imaging: navigator echo biofeedback increases navigator efficiency--initial experience.
abstract: OBJECTIVE
  The aim of this study was to investigate whether a respiratory biofeedback system could increase navigator efficiency and maintain image quality compared to conventional respiratory-gated magnetic resonance coronary angiography (MRCA).
  
  
  METHODS
  Eighteen healthy volunteers underwent MRCA using three different respiratory-gating protocols. A conventional expiratory free-breathing (FB) sequence was compared to two approaches using navigator echo biofeedback (NEB), a midinspiratory approach (NEBin) and an expiratory approach (NEBex). Navigator data reflecting the position of the diaphragm relative to a 3-mm gating window were made available to the subject using a video projector in combination with a Plexiglas screen and mirror goggles. Image quality was graded by two radiologists in consensus using a visual score ranging from 1 (not visible) to 4 (excellent vessel depiction).
  
  
  RESULTS
  The NEB approaches improved navigator efficiency (71.1% with NEBex and 68.0% with NEBin vs 42.2% with FB), thus reducing total imaging time. This difference was statistically significant (P(NEBin)=.007; P(NEBex)=.001). Image quality in the NEBex group was comparable to that in the FB group (median score, 2.44 vs 2.52), but it proved to be significantly lower (median score, 1.94 vs 2.52) for the right coronary artery and the left anterior descending coronary artery in the NEBin group.
  
  
  CONCLUSIONS
  NEB maintains image quality and significantly increases navigator efficiency, thereby decreasing total imaging time by about 40% compared to a conventional FB acquisition strategy.
authors.affiliation: Department of Diagnostic and Interventional Radiology, University of Ulm, Steinhoevelstrasse 9, 89075 Ulm, Germany. sfeuerlein@yahoo.com
authors.forename: Sebastian
authors.initials: S
authors.lastname: Feuerlein
authors.forename: Oliver
authors.initials: O
authors.lastname: Klass
authors.forename: Alberto
authors.initials: A
authors.lastname: Pasquarelli
authors.forename: Hans-Juergen
authors.initials: HJ
authors.lastname: Brambs
authors.forename: Arthur
authors.initials: A
authors.lastname: Wunderlich
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Duerk
authors.forename: Andrik J
authors.initials: AJ
authors.lastname: Aschoff
authors.forename: Martin H K
authors.initials: MH
authors.lastname: Hoffmann
mesh_terms: D000328:Adult; D001676:Biofeedback, Psychology / Q000379:methods*; D003331:Coronary Vessels / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D010865:Pilot Projects; D015203:Reproducibility of Results; D015656:Respiratory Mechanics; D012680:Sensitivity and Specificity; D055815:Young Adult