Spatial and spectral anisotropy in HARP images: An automated approach
Strain and related tensors play a major role in cardiac function characterization, so correct estimation of the local phase in tagged images is crucial for quantitative myocardial motion studies. We propose an Harmonic Phase related procedure that is adaptive in the spatial and the spectral domains: as for the former, we use an angled-steered analysis window prior to the Fourier Transform; as for the latter, the bandpass filter is also angle-adaptive. Both of them are narrow in the modulation direction and wide in the orthogonal direction. Moreover, no parameters are manually set since their values are partially based on the information available at the DICOM headers and additional information is estimated from data. The procedure is tested in terms of accuracy (on synthetic data) and reproducibility (on real data) of the deformation gradient tensor, measured by means of the distribution of the Frobenius norm differences between two tensor datasets.