title: Accurate two-dimensional cardiac strain calculation using adaptive windowed Fourier transform and Gabor wavelet transform.
abstract: OBJECTIVE
  Cardiac strain calculated from tagged magnetic resonance (MR) images provides clinicians information about abnormalities of heart-wall motion in patients. It is important to develop an accurate method to determine the cardiac strain efficiently. An adaptive windowed harmonic phase (AWHARP) method is proposed for cardiac strain calculation.
  
  
  METHODS
  AWHARP is based on adaptive windowed Fourier transform (AWFT) and 2D Gabor wavelet transform (2D-GWT). The AWFT provides a spatially varying representation of the signal spectra, which allows the harmonic phase (HARP) image to be extracted with high accuracy. Instantaneous spatial frequencies are calculated using 2D-GWT, and the widths of the adaptive windows are then determined according to the instantaneous spatial frequencies for multi-resolution analysis of phase extraction. The proposed method was studied using simulated images and patients' MR images. Both single tagged images (SPAMM) and subtracted tagged images (CSPAMM) were generated using our simulation method, and their results calculated using AWHARP and HARP methods were compared. Normal and pathological tagged MR images were also processed to evaluate the performance of our method.
  
  
  RESULTS
  Our experimental results show that the accuracies of phase and strain images calculated using the AWHARP method are higher than that calculated using the HARP method especially for large tag line deformation. The improvement in accuracies can be up to 3.2 strain (E1) and 17.3 calculation from MR images reveals that the cardiac strain in the end-systolic state is significantly reduced for patients with hypertrophic cardiomyopathy (HCM) compared to that of healthy subjects.
  
  
  CONCLUSIONS
  The proposed AWHARP is an accurate and efficient method for cardiac strain estimation from MR images. This new algorithm can help clinicians to detect left ventricle dysfunctions and myocardial diseases with accurate cardiac strain analysis.
authors.affiliation: Department of Mechanical Engineering, National University of Singapore, Singapore, Singapore. g0800248@nus.edu.sg
authors.forename: Y B
authors.initials: YB
authors.lastname: Fu
authors.forename: C K
authors.initials: CK
authors.lastname: Chui
authors.forename: C L
authors.initials: CL
authors.lastname: Teo
mesh_terms: D000465:Algorithms; D005583:Fourier Analysis; D006321:Heart / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D009200:Myocardial Contraction / Q000502:physiology*; D058067:Wavelet Analysis