Myocardial Deformation from Local Frequency Estimation in Tagging MRI

We consider a new method to analyse deformation of the myocardial wall from tagging magnetic resonance images. The method exploits the fact that a regular pattern of stripe tags induces a timedependent frequency covector field tightly coupled to the myocardial tissue and not affected by tag fading. The corresponding local frequency can be disambiguated with the help of the Gabor transform. The transformation of the tagging frequency covector field is governed by the deformation tensor field. Reversely, the deformation (and strain) tensor field can be retrieved from local frequency estimates given at least n (independent) tagging sequences, where n denotes spatial dimension. For the sake of illustration we consider the conventional case n = 2. Moreover, we make use of an overdetermined system by exploiting 4 instead of 2 tagging directions, which contributes to the robustness of the results. The method does not require explicit knowledge of material motion or tag line extraction. Displacement estimations are compared to HARP.