title: Extraction of left-ventricular torsion angle from the long-axis view by block-matching algorithm: Comparison with the short-axis view.
abstract: BACKGROUND
  Due to limitations in measuring the torsion angle in the short-axis view when studying through-plane motion and so it is dependent on reference levels, in this study, we follow myocardial movement along the long-axis of the left ventricle (LV). Then, LV torsion is estimated in the long-axis view and compared with LV torsion in the short-axis view.
  
  
  METHODS
  Two dimensional echocardiographic images of healthy persons were recorded in cine loop format position throughout four cardiac cycles at basal and apical levels in the long- and short-axis views. The motion vectors for reign of interest in the horizontal and vertical directions were obtained by block matching algorithm. Correlation between the values of automated analysis and manual tracing was performed by Pearson correlation analysis. Then, the maximum rotation angles of the short- and long-axis views at basal and apical levels were assessed. Left-ventricular torsion angles in short-axis and long-axis views were calculated and compared based on rotation angles.
  
  
  RESULTS
  There was a high correlation between the measured myocardial wall displacement of automated analysis (BM algorithm) and manual tracing (R=0.96, p<0.05). The maximum rotation angles of basal and apical levels in the short-axis view are 7.96±1.57° and 9.49±1.72° and so in the long-axis view are 18.51±3.41° and 14.74±2.91°, respectively. The LV torsion angles and the time to reach peak LV torsion angles in the short-axis views are 17.26±2.53°, 293±26ms and in the long-axis view are 32.26±5.60° and 290±22ms respectively. There was a high correlation between the left-ventricular torsion angle in the short-axis view and the long-axis view (R=0.92, p<0.05). There was also a high correlation between the time to reach peak left-ventricular torsion angle in the short-axis view as compared to the long-axis view (R=0.97, p<0.05).
  
  
  CONCLUSIONS
  This study suggested that the LVtorsion angles in the short- and long-axis views were significantly correlated. It is concluded that torsion and rotation angles in the long-axis view are similar to those determined using the short-axis view.
authors.affiliation: Department of Medical Physics, Tarbiat Modares University, Tehran, Iran.
authors.forename: Zahra
authors.initials: Z
authors.lastname: Arab-Baferani
authors.forename: Manijhe
authors.initials: M
authors.lastname: Mokhtari-Dizaji
authors.forename: Farideh
authors.initials: F
authors.lastname: Roshanali
mesh_terms: D000465:Algorithms; D004452:Echocardiography; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D009200:Myocardial Contraction; D016277:Ventricular Function, Left