Research On Adaptive Beamforming Algorithm And Ultrasonic Imaging Based On Compressed Sensing Technology

Ultrasound imaging is widely used in clinical diagnosis and industrial detection because of its safety,real time,painless and low cost.But comparing with MRI,CT,X ray imaging technology,the ultrasound imaging has a low spatial resolution,easy to be disturbed,and the image frame rate is not high enough.Moreover,the demand of the quality of ultrasound imaging is becoming higher and higher with the improvement of technology.Therefore it is urgent to solve the problems in ultrasound imaging.The following 2 aspects of adaptive digital beamforming and ultrasonic imaging based on compressed sensing technology are studied in this paper.?1?Beamforming is one of the key factors affect the output of imaging in ultrasonic imaging.The traditional Minimum Variance adaptive beamforming algorithm can improve the imaging resolution in a certain extent,but the contrast improvement is not obvious,and the robustness to noise decreasing in strong correlation interference.In view of the problem,a signal to noise ratio dependent postfilter combined with eigenspacebased Minimum Variance algorithm is proposed.This method is based on the separability of the ultrasonic echo signal to improve the image contrast by projecting the weight vector of the Minimum Variance into the signal subspace.And then,design the postfilter based on the signal coherence and introduce the noise weighting coefficients based on SNR to improve the performance of noise reduction caused by covariance matrix estimation error.To verify the effectiveness of the algorithm,the contrast experiment of point targets,speckle objects and geabr₀ experimental data of the Michigan University was carried out based on the Field II platform.The experimental results showed that the proposed algorithm can improve the resolution,contrast and the robustness to noise.?2?The technology of high frequency sampling,Synthetic Aperture and expanded array can also improve the imaging quality by increasing the echo data in ultrasonic imaging system,but a large number of echo data will make the complexity of the sampling,transmission and storage increasing.In this regard,a sparse dictionary design for ultrasonic imaging is proposed in this paper.The sparse dictionary makes full use of the characteristic of the ultrasonic echo,which is the emission pulse's attenuate,delay and superpose.So it enhances the sparse representation capability of the echo data,and can make the sparsity of the signal equal to the number of received echo in theory.Such high compression rate can make the reality of the reconstruction of original data in high precision and reduce the complexity of ultrasonic imaging system.In the end,by the comparison and simulation experiments,it is verified that,in the same condition,the reconstructed signal is closer to the original by using the proposed sparse dictionary,the reconstruction accuracy is higher,and the needed time is the least,comparing with the traditional sparse transformations.