Source effects in SWIPE: shear-wave-assisted ultrasound imaging.

SWIPE is a novel method for ultrasonic image reconstruction that uses echo phase modulation induced by traveling shear waves to decipher lateral k-space image data. Our prior experimental work has demonstrated lateral resolution with SWIPE at higher than expected sidelobe levels. Here we examine the effect of the location of the mechanical excitation source used in SWIPE. Surface and internal sources were simulated using finite element modeling. The interaction of shear and surface (Rayleigh) waves was found to degrade the SWIPE point spread function when surface excitation was employed. Internal excitation was not negatively affected and yielded near-ideal results. Regions of ideal performance, simulated point spread functions, and phase non-linearity measurements for the two methods are presented. The results indicate that internal sources, e.g. acoustic radiation force, can be expected to yield high-quality SWIPE images.