Near-Field, Broadband Adaptive Beamforming for Ultrasound Imaging
Francesco Viola, Michael A. Ellis, William F. Walker · 2006
For over fifty years adaptive beamforming (ABF) algorithms have been applied in RADAR and SONAR signal processing. These algorithms reduce the contribution of undesired off-axis signals while maintaining a desired response along a specific look direction. Typically, ABF achieves higher resolution and contrast than conventional beamforming (CBF), at the price of an increased computational load. In this paper we describe a novel ABF designed for medical ultrasound, named the time-domain optimized near-field estimator, or TONE. We performed a series of simulations using ultrasound data to test the performance of this algorithm and compare it to conventional, data independent, delay and sum beamforming. We also performed experiments using a Philips SONOS 5500. CBF was applied using the default parameters of the Philips scanner, whereas TONE was applied on single-channel, unfocused data with plane wave transmit. TONE images were reconstructed at a sampling of 67 mum laterally and 19 mum axially. The results obtained for a series of 5 20 mum wires in a water tank show a significant improvement in spatial resolution when compared to CBF. We also analyzed the performance of TONE as a function of speed of sound errors and array sparsity, finding TONE robust to both.