Phase Modulation Beamforming for Ultrafast Plane-Wave Imaging.

In order to improve the spatial resolution for high-frame-rate imaging, a new image formation approach is proposed based on introducing very weak aberration into received data, then combining the multiple results by taking the pixel-wise standard deviation of multiple aberrated images and subtracting the result from the delay-and-sum image. This approach is demonstrated in simulations, tissue-mimicking phantom experiments, and in vivo imaging. Simulations indicate the lateral full-width half-maximum (FWHM) of targets decreases by 38.24% ± 6.38%. In imaging wire targets in a tissue-mimicking phantom at 7.8 MHz, wire target FWHM decreases by 35.91% ± 5.39%. However, contrast was observed to decrease by 1.23 dB and contrast-to-noise ratio (CNR) by 18.5% in phantom studies due to the subtraction of similar images, which increases the number of dark pixels in the image. Finally, the proposed technique is tested in vivo, with images showing improvements similar to those in tissue-mimicking phantoms, including increased separation between closely spaced targets.