Research On Beamforming Algorithm Of Plane Wave Ultrasound Imaging

Plane Wave imaging(PWI) can achieve high temporal resolution, and have become the most commonly used imaging mode in ultrafast ultrasound imaging. Now be widely used in new ultrasound technology such as elastography. However, due to the wide transmit beam width, PWI suffers from low SNR in echo signal, which resulting poor image quality and limiting its development. Beamformer is the key component of ultrasound imaging system and directly determines the image quality. So the research on beamforming algorithm can play an important role on improving the image quality of PWI.Firstly, the basic theory of ultrasound imaging, the methods of beam control and delay-and-sum algorithm are been introduced and analyzed, an point target simulation experiment illustrates that traditional beamforming method cannot improve the resolution and contrast in the same time.Then the study have been made on the adaptive beamforming and spatial compound imaging(SCI) which are commonly used in PWI, and proposed two new algorithms to solve the shortcomings of adaptive beamforming and SCI:(1) A adaptive bemforming method which combines the eigenspace-based minimum variance (ESBMV) with sign coherence factor (SCF) is proposed to solve the drawbacks in ESBMV which cannot improve resolution and contrast in the same time. Simulations of point target and cyst target are used to verify the effectiveness of the improved algorithm. Simulation results show that:compare to ESBMV, the proposed algorithm made an improvement of 42% in resolution and 6.7% in contrast.(2) In order to reduce the compounding times while maintain the high image quality,a SCI algorithm based on minimum variance(MV) is proposed. Such algorithms can combine the high resolution of MV and high contrast of SCI to achieved a high quality, Point target and cyst target simulation result shows that:the proposed method made an improvement of 39.4% in resolution compare to SCI; when in the same compounding time,the proposed method have higher CR; In 5 times compounding,CR of the proposed method is higher than that of SCI in 21.Finally, in order to verify if the two proposed methods have the practical feasibility, a point t phantom and carotid artery are used as imaging target. The results show the same conclusions as in the simulation experiment, which illustrate that the proposed methods can be used in actual PWI system to improve the image quality.