A synthetic aperture focusing technique with optimized beamforming for high-frequency ultrasound

At last year's conference, we presented a synthetic aperture image reconstruction technique (PSF-SAFT) for fixed-focus single-element ultrasound transducers. It is based on the correlation of the recorded echo signals with the simulated depth-dependent point spread function (PSF) of the ultrasound imaging system. Compared to conventional delay-and-sum (DAS) methods, it results in a higher signal-to-noise-ratio (SNR) but lower axial and lateral resolution. In this contribution the synthetic aperture focusing technique is further developed by inverse filtering of the simulated PSFs and coherence factor (CF) weighting for increased resolution and suppression of side lobes, respectively. The proposed method was evaluated using a 20 MHz ultrasound system with a spherically-focused transducer. With measurements on a wire phantom the transducer's resolution in focus was determined and compared to DAS-SAFT and PSF-SAFT processed datasets, with and without CF-weighting. While the spatial resolution does not differ significantly, PSF-SAFT with CF-weighting results in the highest reduction of noise and side lobes.