Methods for the estimation of sub-sample motion of digitized ultrasound echo signals in two dimensions

Motion estimation in sequences of ultrasound echo signals is essential for a wide range of modern ultrasound-based signal processing applications. Pattern matching algorithms are generally used for finding the motion within sampling accuracy. Subsequently, 1D interpolation techniques are employed to find any motion smaller than sampling accuracy. In this paper, we propose several interpolation schemes that are suited for 2D motion estimation. Simulations using Field II ultrasound simulation software and experiments using an Ultrasonix Sonix RP imaging system with a L9-4/38 linear array transducer are used to study these techniques and compare their performance to other methods reported in the literature. The results show that the proposed interpolation methods outperform other common techniques in terms of bias and jitter. The axial and the lateral bias of the proposed methods are measured to be less than 1 microm and 5 microm, respectively, in both the simulated and the experimental data.