title: Deformation analysis of 3D tagged cardiac images using an optical flow method.
abstract: BACKGROUND
  This study proposes and validates a method of measuring 3D strain in myocardium using a 3D Cardiovascular Magnetic Resonance (CMR) tissue-tagging sequence and a 3D optical flow method (OFM).
  
  
  METHODS
  Initially, a 3D tag MR sequence was developed and the parameters of the sequence and 3D OFM were optimized using phantom images with simulated deformation. This method then was validated in-vivo and utilized to quantify normal sheep left ventricular functions.
  
  
  RESULTS
  Optimizing imaging and OFM parameters in the phantom study produced sub-pixel root-mean square error (RMS) between the estimated and known displacements in the x (RMSx = 0.62 pixels (0.43 mm)), y (RMSy = 0.64 pixels (0.45 mm)) and z (RMSz = 0.68 pixels (1 mm)) direction, respectively. In-vivo validation demonstrated excellent correlation between the displacement measured by manually tracking tag intersections and that generated by 3D OFM (R >or= 0.98). Technique performance was maintained even with 20% Gaussian noise added to the phantom images. Furthermore, 3D tracking of 3D cardiac motions resulted in a 51% decrease in in-plane tracking error as compared to 2D tracking. The in-vivo function studies showed that maximum wall thickening was greatest in the lateral wall, and increased from both apex and base towards the mid-ventricular region. Regional deformation patterns are in agreement with previous studies on LV function.
  
  
  CONCLUSIONS
  A novel method was developed to measure 3D LV wall deformation rapidly with high in-plane and through-plane resolution from one 3D cine acquisition.
authors.affiliation: Department of Radiology, 1 Silverstein, 3400 Spruce Street, Philadelphia, PA 19104, USA.
authors.forename: Chun
authors.initials: C
authors.lastname: Xu
authors.forename: James J
authors.initials: JJ
authors.lastname: Pilla
authors.forename: Gamaliel
authors.initials: G
authors.lastname: Isaac
authors.forename: Joseph H
authors.initials: JH
authors.lastname: Gorman
authors.forename: Aaron S
authors.initials: AS
authors.lastname: Blom
authors.forename: Robert C
authors.initials: RC
authors.lastname: Gorman
authors.forename: Zhou
authors.initials: Z
authors.lastname: Ling
authors.forename: Lawrence
authors.initials: L
authors.lastname: Dougherty
mesh_terms: D000818:Animals; D016477:Artifacts; D003198:Computer Simulation; D007090:Image Interpretation, Computer-Assisted; D021621:Imaging, Three-Dimensional; D019028:Magnetic Resonance Imaging, Cine / Q000295:instrumentation*; D009200:Myocardial Contraction; D019047:Phantoms, Imaging; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012756:Sheep; D013997:Time Factors; D018487:Ventricular Dysfunction, Left / Q000175:diagnosis* / Q000503:physiopathology; D016277:Ventricular Function, Left