title: Accuracy, reproducibility, and comparability of Doppler tissue imaging by two high-end ultrasound systems.
abstract: BACKGROUND
  Doppler tissue imaging is a new technology for quantitative evaluation of myocardial motion and contractility, and is available in several ultrasound systems. This study evaluates the comparability, accuracy, and reproducibility of measurements of velocity, strain rate, and strain by two high-end ultrasound systems.
  
  
  METHODS
  Accuracy was assessed by imaging a tissue-mimicking gelatin phantom, and the comparability of measurements in the right ventricular free wall and interventricular septum was assessed in 20 healthy participants. Reproducibility was evaluated by repeated recordings in vitro and in a random subset of patients.
  
  
  RESULTS
  In vitro, a high degree of accuracy was found in both systems, with one system measuring slightly lower values than the reference values (mean difference 0.35 +/- 0.18 cm/s, P < .001). Values higher than the reference values were measured by both systems for strain and strain rate. In vivo, no systematic differences in measured velocities, strain rate, and strain were found; however, wide limits of agreement were seen for strain and strain rate. Measurements of tissue velocity, strain, and strain rate were well reproducible, nevertheless wide variation was found in both systems (coefficient of variation = 9%-19%).
  
  
  CONCLUSIONS
  For clinical purposes, both systems have sufficient accuracy for measurements of tissue velocity. The variation in measurements of strain rate and strain by Doppler tissue imaging should be taken into account when designing studies using this new technology. Approaches to potentially reduce this variation should be addressed in future studies.
authors.affiliation: Mayo Clinic College of Medicine, Rochester, Minnesota, USA. jesper.kjaergaard@dadlnet.dk
authors.forename: Jesper
authors.initials: J
authors.lastname: Kjaergaard
authors.forename: Josef
authors.initials: J
authors.lastname: Korinek
authors.forename: Marek
authors.initials: M
authors.lastname: Belohlavek
authors.forename: Jae K
authors.initials: JK
authors.lastname: Oh
authors.forename: Peter
authors.initials: P
authors.lastname: Sogaard
authors.forename: Christian
authors.initials: C
authors.lastname: Hassager
mesh_terms: D015150:Echocardiography, Doppler / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005260:Female; D006352:Heart Ventricles / Q000000981:diagnostic imaging*; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation* / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation* / Q000379:methods; D008297:Male; D008875:Middle Aged; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013314:Stress, Mechanical; D013318:Stroke Volume; D016276:Ventricular Function; D016277:Ventricular Function, Left / Q000502:physiology*