title: 3D left ventricular strain from unwrapped harmonic phase measurements.
abstract: OBJECTIVE
  To validate a method for measuring 3D left ventricular (LV) strain from phase-unwrapped harmonic phase (HARP) images derived from tagged cardiac magnetic resonance imaging (MRI).
  
  
  METHODS
  A set of 40 human subjects were imaged with tagged MRI. In each study the HARP phase was computed and unwrapped in each short-axis and long-axis image. Inconsistencies in unwrapped phase were resolved using branch cuts manually placed with a graphical user interface. 3D strain maps were computed for all imaged timeframes in each study. The strain from unwrapped phase (SUP) and displacements were compared to those estimated by a feature-based (FB) technique and a HARP technique.
  
  
  RESULTS
  3D strain was computed in each timeframe through systole and mid-diastole in approximately 30 minutes per study. The standard deviation of the difference between strains measured by the FB and the SUP methods was less than 5% of the average of the strains from the two methods. The correlation between peak circumferential strain measured using the SUP and HARP techniques was over 83%.
  
  
  CONCLUSIONS
  The SUP technique can reconstruct full 3D strain maps from tagged MR images through the cardiac cycle in a reasonable amount of time and user interaction compared to other 3D analysis methods.
authors.affiliation: Electrical and Computer Engineering Department, Auburn University, Auburn, Alabama 36849-5201, USA.
authors.forename: Bharath Ambale
authors.initials: BA
authors.lastname: Venkatesh
authors.forename: Himanshu
authors.initials: H
authors.lastname: Gupta
authors.forename: Steven G
authors.initials: SG
authors.lastname: Lloyd
authors.forename: Louis
authors.initials: L
authors.lastname: Dell 'Italia
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Denney
mesh_terms: D000465:Algorithms; D016022:Case-Control Studies; D015331:Cohort Studies; D006352:Heart Ventricles / Q000473:pathology*; D006801:Humans; D006973:Hypertension / Q000473:pathology; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008944:Mitral Valve Insufficiency / Q000473:pathology; D015233:Models, Statistical; D009203:Myocardial Infarction / Q000473:pathology; D013997:Time Factors; D016277:Ventricular Function, Left