A coherence-based correction method was proposed in order to improve the lateral resolution and enhance the contrast of medical ultrasound imaging in the presence of phase aberration. The averaged coherence factor was proposed at first and used as a metric to evaluate phase aberration correction. By maximizing the averaged coherence factor, the time delay parameter of each channel was adjusted. A new set of coherence factors was calculated and the corrected data was optimized to form the final B-mode image. The simulations on point targets and a cyst phantom showed that the proposed method outperformed the nearest neighboring cross correlation method and conventional coherence-weighting method, and the lateral resolution and contrast ratio was improved by approximately 0.24mm and 18dB respectively. The proposed method combined the advantages of phase error correction and coherence-weighting, which could improve imaging qualities effectively in medical ultrasound.
In synthetic transmit aperture medical ultrasound imaging field,a compressed sensing ultrasound imaging method based on the sparsity in frequency domain is presented in order to reduce huge amount of data and large numbers of receiving channels.First,the sparsity in frequency domain is verified.Then the echo signal is compressively sampled in time-spatial domain based on compressed sensing and the echo signal is reconstructed by solving an optimization problem.Finally the image is made by using the synthetic transmit aperture approach.The experiments based on point target and fetus target are used to verify the proposed method.The MSE,resolution and image quality of reconstructed image and those of original image are compared and analyzed.The results show that only 30%amount of data and 50%of receiving channels were used to implement ultrasound imaging without reducing the quality of image in experiment.The amount of data and the complexity of system are reduced greatly by the proposed method based on compressed sensing.
