The effect of PSF spatial-variance and nonlinear transducer geometry on motion estimation from echocardiography

Two-dimensional echocardiography continues to be the most widely used modality for the assessment of cardiac function due to its effectiveness, ease of use, and low costs. Echocardiographic images are derived from the mechanical interaction between the ultrasound field and the contractile heart tissue. Previously, in [6], based on B-mode echocardiographic simulations, we showed that motion estimation errors are significantly higher in shift-varying simulations when compared to shift-invariant simulations. In order to ascertain the effect of the spatial variance of the Ultrasonic field point spread function (PSF) and the transducer geometry on motion estimation, in the current paper, several simple canonical cardiac motions such as translation in axial and horizontal direction, and out-of-plane motion were simulated and the motion estimation errors were calculated. For axial motions, the greatest angular errors occurred within the lateral regions of the image, irrespective of the motion estimation technique that was adopted. We hypothesize that the transducer geometry and the PSF spatial-variance were the underlying sources of error for the motion estimation methods. No similar conclusions could be made regarding motion estimation errors for azimuthal and out-of-plane ultrasound simulations.