Adaptive scaled Wiener postfilter beamformer for ultrasound imaging

In ultrasound imaging Wiener postfilter and coherent factor (CF) concepts were combined with minimum variance (MV) and eigenspace-based MV (ESBMV) beamformers to future suppress sidelobes and to improve the imaging contrast and the spatial resolution. CF, which can be considered as a scaled Wiener postfilter with high noise power weighting, provides high imaging resolution. The high resolution, however, is achieved with the contrast as a sacrifice. On other hand, Wiener postfilter, provides better signal intensity restoration and imaging contrast than CF but with lower imaging resolution. To pursue the optimal imaging contrast of Wiener postfilter and the high resolution of CF at the same time, an adaptive scaled Wiener postfilter beamformer (ASC-Wiener) is proposed. In proposed method, the noise power weighting of Wiener postfilter is adjusted adaptively so that related to the output SNR inversely needless to estimate the input SNR. Simulation and real data experiment for target point imaging show the high performance of the proposed beamformer in terms of the imaging resolution and sidelobes suppression. Cyst phantom imaging also shows that the ASC-Wiener preserves the speckle intensity and improves the imaging contrast. The contrast ratio (CR) and the contrast-to-noise ratio (CNR) are improved by 6.2/0.35 dB over ESBMV-Wiener and by 20.7/0.65 over ESBMV-CF. These results solidly prove that the imaging contrast and the imaging resolution are improved significantly and simultaneously.