title: [Flow quantification in coronary and bypass vessels with MR phase contrast technique].
abstract: OBJECTIVE
  To evaluate accuracy of velocity encoded cine MR imaging for determination of blood flow in coronary arteries and coronary bypass grafts.
  
  
  METHODS
  12 patients with 22 coronary bypass grafts underwent intraoperative flow quantification using the transit time ultrasound method. These values were compared to postoperative MR phase shift measurements. Flow measurements were performed preoperatively in 28 coronary arteries of 20 patients. For flow measurement, we used a velocity-encoded k-space segmented gradient echo sequence with a temporal resolution of 110 or 125 ms, respectively. 6-8 pase shift images could be acquired during one cardiac cycle.
  
  
  RESULTS
  There was a significant correlation between intraoperative and flow measurements using velocity-encoded MR imaging (r = 0.74, p < 0.0001, t-test). Flow volumes determined by MR imaging were systematically larger than those determined by the transit time ultrasound method. Mean flow in coronary arteries was reduced in severely stenosed vessels (> 70%) compared to normal vessels. Intra- and interobserver variability were 10.5 and 15% (coronary bypass grafts), and 12.3 and 15.8% (coronary arteries), respectively.
  
  
  CONCLUSIONS
  Velocity-encoded MR imaging enables determination of flow in coronary artery bypass grafts and coronary arteries. Future developments should aim at the improvement of spatial and temporal resolution of the method.
authors.affiliation: Klinik und Poliklinik für Radiologie, Johannes-Gutenberg-Universität Mainz. kreitner@radiologie.klinik.uni-mainz.de
authors.forename: K F
authors.initials: KF
authors.lastname: Kreitner
authors.forename: T
authors.initials: T
authors.lastname: Voigtländer
authors.forename: T
authors.initials: T
authors.lastname: Wittlinger
authors.forename: M
authors.initials: M
authors.lastname: Dahm
authors.forename: P
authors.initials: P
authors.lastname: Kalden
authors.forename: J
authors.initials: J
authors.lastname: Meyer
authors.forename: M
authors.initials: M
authors.lastname: Thelen
mesh_terms: D000328:Adult; D000368:Aged; D001026:Coronary Artery Bypass; D003326:Coronary Circulation / Q000502:physiology*; D003936:Diagnosis, Computer-Assisted / Q000295:instrumentation; D005260:Female; D006083:Graft Occlusion, Vascular / Q000175:diagnosis* / Q000503:physiopathology; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation*; D018810:Magnetic Resonance Angiography / Q000295:instrumentation*; D008297:Male; D008875:Middle Aged; D012212:Rheology / Q000295:instrumentation*; D012680:Sensitivity and Specificity