title: Estimation of radial strain and rotation using a new algorithm based on speckle tracking.
abstract: BACKGROUND
  The aim of this study was to test the ability of a new algorithm to accurately measure point-to-point Lagrangian strain (LS) and local rotation (ROT). Change in distance between 2 separate regions of interest (ROIs) can theoretically be computed with speckle tracking (SpT) and used to calculate LS in any tissue location with angle independence and high spatial resolution. Similarly, tracking an ROI relative to a fixed point should provide an estimate of ROT.
  
  
  METHODS
  Two dynamic phantoms (60 beats/min) were scanned in short axis at frame rates of 30, 60, and 90 Hz. To estimate LS, 2 ROIs were positioned immediately beneath the inner and outer borders of the superior wall of the first phantom and tracked using SpT. LS derived from SpT (SpT-LS) was compared with LS measured by sonomicrometers placed on the inner and outer walls of the phantom (SN-LS). To estimate ROT, the rotational vectors around the centroid of a second phantom were calculated for 3 epicardial bead targets imaged with gated computed tomography (CT) and compared with measurements derived from SpT.
  
  
  RESULTS
  There was a significant correlation between SpT-LS and SN-LS at 30 Hz (R(2) = 0.99; P < .0001), 60 Hz (R(2) = 0.98; P < .0001), and 90 Hz (R(2) = 0.99; P < .0001). There was also a significant correlation between ROT derived from SpT and ROT derived from CT: R(2) = 0.97 (P < .0001) at 30 Hz, R(2) = 0.95 (P < .0001) at 60 Hz, and R(2) = 0.98 (P < .0001) at 90 Hz.
  
  
  CONCLUSIONS
  Point-to-point SpT permits the determination of LS between 2 distinct tissue regions as well as ROT measurement of specific tissue regions without the need for border detection.
authors.affiliation: Cardiac Ultrasound Laboratory, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA. ftournoux@gmail.com
authors.forename: François
authors.initials: F
authors.lastname: Tournoux
authors.forename: Raymond C
authors.initials: RC
authors.lastname: Chan
authors.forename: Mark D
authors.initials: MD
authors.lastname: Handschumacher
authors.forename: Ivan S
authors.initials: IS
authors.lastname: Salgo
authors.forename: Robert
authors.initials: R
authors.lastname: Manzke
authors.forename: Scott
authors.initials: S
authors.lastname: Settlemier
authors.forename: J Luis
authors.initials: JL
authors.lastname: Guerrero
authors.forename: Ricardo C
authors.initials: RC
authors.lastname: Cury
authors.forename: Arthur E
authors.initials: AE
authors.lastname: Weyman
authors.forename: Michael H
authors.initials: MH
authors.lastname: Picard
mesh_terms: D000465:Algorithms; D004452:Echocardiography / Q000379:methods*; D055119:Elastic Modulus; D054459:Elasticity Imaging Techniques / Q000379:methods*; D006321:Heart / Q000502:physiology*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D019047:Phantoms, Imaging; D012399:Rotation; D013314:Stress, Mechanical