Evaluation of the Transverse Oscillation Technique for Cardiac Phased Array Imaging: A Theoretical Study
Abstract: The transverse oscillation (TO) technique can improve the estimation of tissue motion perpendicular to the ultrasound beam direction. TOs can be introduced using plane wave (PW) insonification and bilobed Gaussian apodization (BA) on receive (abbreviated ass PWTO). Furthermore, the TO frequency of PWTO can be doubled after a heterodyning demodulation process is performed (abbreviated as PWTO*). This paper is concerned with identifying the limitations of the PWTO technique in the specific context of myocardia myocardiall deformation imaging with phased arrays and investigating the conditions in which it remains advantageous over traditional focused (FOC) beamforming. For this purpose, several tissue phantoms were simulated using Field II, undergoing a wide range of displacement displ magnitudes and modes (lateral, axial, and rotational motions). The Cramer-Rao Cramer lower bound was used to optimize TO beamforming parameters and theoretically predict the fundamental tracking performance limits associated with the FOC, PWTO, and PWTO* beamforming scenarios. This framework was extended to also predict the performance for BA functions that are windowed by the physical aperture of the transducer, leading to higher lateral oscillations. It was found that windowed BA functions resulted in lo lower wer jitter errors compared with traditional BA functions. PWTO* outperformed FOC at all investigated signal signal--to-noise ratio (SNR) levels but only up to a certain displacement, with the advantage rapidly