title: The influence of frame rate on two-dimensional speckle-tracking strain measurements: a study on silico-simulated models and images recorded in patients.
abstract: OBJECTIVE
  Ultrasound-derived myocardial strain can render valuable diagnostic and prognostic information. However, acquisition settings can have an important impact on the measurements. Frame rate (i.e. temporal resolution) seems to be of particular importance. The aim of this study was to find the optimal range of frame rates needed for most accurate and reproducible 2D strain measurements using a 2D speckle-tracking software package.
  
  
  RESULTS
  Synthetic two dimensional (2D) ultrasound grey-scale images of the left ventricle (LV) were generated in which the strain in longitudinal, circumferential, and radial direction were precisely known from the underlying kinematic LV model. Four different models were generated at frame rates between 20 and 110 Hz. The resulting images were repeatedly analysed. Results of the synthetic data were validated in 66 patients, where long- and short-axis recordings at different frame rates were analysed. In simulated data, accurate strain estimates could be achieved at >30 frames per cycle (FpC) for longitudinal and circumferential strains. Lower FpC underestimated strain systematically. Radial strain estimates were less accurate and less reproducible. Patient strain displayed the same plateaus as in the synthetic models. Higher noise and the presence of artefacts in patient data were followed by higher measurement variability.
  
  
  CONCLUSIONS
  Standard machine settings with a FR of 50-60 Hz allow correct assessment of peak global longitudinal and circumferential strain. Correct definition of the region of interest within the myocardium as well as the reduction of noise and artefacts seem to be of highest importance for accurate 2D strain estimation.
authors.affiliation: Division of Cardiothoracic and Respiratory Medicine, Department of Cardiology, University Hospital of Northern Norway, 9038 Tromsø, Norway assami.rosner@unn.no.
authors.forename: Assami
authors.initials: A
authors.lastname: Rösner
authors.affiliation: Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium Life and Health Sciences Research Institute, University of Minho, Minho, Portugal.
authors.forename: Daniel
authors.initials: D
authors.lastname: Barbosa
authors.affiliation: Department of Clinical Medicine, Arctic University of Norway, Tromsø, Norway.
authors.forename: Erling
authors.initials: E
authors.lastname: Aarsæther
authors.affiliation: Division of Cardiothoracic and Respiratory Medicine, Department of Cardiology, University Hospital of Northern Norway, 9038 Tromsø, Norway.
authors.forename: Didrik
authors.initials: D
authors.lastname: Kjønås
authors.affiliation: Division of Cardiothoracic and Respiratory Medicine, Department of Cardiology, University Hospital of Northern Norway, 9038 Tromsø, Norway Department of Clinical Medicine, Arctic University of Norway, Tromsø, Norway.
authors.forename: Henrik
authors.initials: H
authors.lastname: Schirmer
authors.affiliation: Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium.
authors.forename: Jan
authors.initials: J
authors.lastname: D'hooge
mesh_terms: D002318:Cardiovascular Diseases / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D003198:Computer Simulation; D004452:Echocardiography / Q000379:methods*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D009200:Myocardial Contraction / Q000502:physiology*; D015203:Reproducibility of Results; D012984:Software
keywords: Frame rate; Imaging quality; Simulated model; Strain imaging