title: Frame rate required for speckle tracking echocardiography: A quantitative clinical study with open-source, vendor-independent software.
abstract: OBJECTIVE
  To determine the optimal frame rate at which reliable heart walls velocities can be assessed by speckle tracking.
  
  
  BACKGROUND
  Assessing left ventricular function with speckle tracking is useful in patient diagnosis but requires a temporal resolution that can follow myocardial motion. In this study we investigated the effect of different frame rates on the accuracy of speckle tracking results, highlighting the temporal resolution where reliable results can be obtained.
  
  
  METHODS
  27 patients were scanned at two different frame rates at their resting heart rate. From all acquired loops, lower temporal resolution image sequences were generated by dropping frames, decreasing the frame rate by up to 10-fold.
  
  
  RESULTS
  Tissue velocities were estimated by automated speckle tracking. Above 40 frames/s the peak velocity was reliably measured. When frame rate was lower, the inter-frame interval containing the instant of highest velocity also contained lower velocities, and therefore the average velocity in that interval was an underestimate of the clinically desired instantaneous maximum velocity.
  
  
  CONCLUSIONS
  The higher the frame rate, the more accurately maximum velocities are identified by speckle tracking, until the frame rate drops below 40 frames/s, beyond which there is little increase in peak velocity. We provide in an online supplement the vendor-independent software we used for automatic speckle-tracked velocity assessment to help others working in this field.
authors.affiliation: Imperial College London, National Heart and Lung Institute, Hammersmith Hospital Campus, London W12 0NN, UK. Electronic address: m.negoita@imperial.ac.uk.
authors.forename: Madalina
authors.initials: M
authors.lastname: Negoita
authors.affiliation: Imperial College London, National Heart and Lung Institute, Hammersmith Hospital Campus, London W12 0NN, UK.
authors.forename: Massoud
authors.initials: M
authors.lastname: Zolgharni
authors.affiliation: Imperial College London, National Heart and Lung Institute, Hammersmith Hospital Campus, London W12 0NN, UK.
authors.forename: Elham
authors.initials: E
authors.lastname: Dadkho
authors.affiliation: University of Verona, Department of Medicine, Section of Cardiology, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Pernigo
authors.affiliation: Imperial College London, National Heart and Lung Institute, Hammersmith Hospital Campus, London W12 0NN, UK.
authors.forename: Michael
authors.initials: M
authors.lastname: Mielewczik
authors.affiliation: Imperial College London, National Heart and Lung Institute, Hammersmith Hospital Campus, London W12 0NN, UK.
authors.forename: Graham D
authors.initials: GD
authors.lastname: Cole
authors.affiliation: Imperial College London, National Heart and Lung Institute, Hammersmith Hospital Campus, London W12 0NN, UK.
authors.forename: Niti M
authors.initials: NM
authors.lastname: Dhutia
authors.affiliation: Imperial College London, National Heart and Lung Institute, Hammersmith Hospital Campus, London W12 0NN, UK.
authors.forename: Darrel P
authors.initials: DP
authors.lastname: Francis
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004452:Echocardiography / Q000379:methods / Q000592:standards*; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods / Q000592:standards*; D008297:Male; D008875:Middle Aged; D012984:Software / Q000592:standards*; D013997:Time Factors
keywords: Frame rate; Myocardial velocity; Sampling frequency; Speckle tracking; Tissue velocity imaging