Diffuse targets for improved contrast in beamforming adapted to target
Adaptive beamforming (ABF) algorithms reduce the contribution of undesired off-axis signals, while maintaining a desired response along a specific look direction. Previously, we have described a novel ABF that can be applied to medical ultrasound, entitled Time-domain Optimized Near-field Estimator (TONE) and demonstrated its ability to achieve significant gains in spatial resolution when compared to conventional, delay-and-sum beamforming (CBF). However, several characteristics of TONE hinder its adoption into medical ultrasound, including the discretized appearance of its images as well as clouds surrounding bright targets, which reduce the overall image contrast. Here, we have altered the system model of TONE from a grid of discrete hypothetical targets to a grid of diffuse hypothetical targets in order to suppress these clouds and the discretized appearance of the image. This modification imposes no additional computational cost at the time of beamforming. We performed a series of simulations and experiments, using both point targets and anechoic regions within speckle backgrounds, to test the performance of diffuse-TONE (dTONE) and compare it to both TONE and CBF. In all instances, dTONE showed a reduced appearance of these clouds and improved image contrast. We also analyzed the performance of dTONE in the presence of varying amounts of electronic noise, finding dTONE to be more robust than TONE to decreases in signal-to-noise ratio (SNR). © 2007 IEEE.