Research On Optimization Methods Of Breast Ultrasound Imaging Based On Ring Array

In recent years,with the increase of incidence rate and the emergence of a younger trend,breast cancer has become a major global female health problem.However,due to the inherent imaging drawbacks in the existing equipment at home and abroad,early screening of breast cancer is difficult.For example,the limited imaging angle results in insufficient information acquisition and the inadequate data processing methods lead to low contrast of the target information;the weak backscattered signal from biological tissue results in poor imaging quality;the high sampling rate and the efficiency of elements reuse lead to large amounts of data collection and hardware damage.To solve the above problems in breast ultrasound imaging,the main work of this paper is as follows:(1)To solve the problem of low imaging quality due to limited angle,ring array transducer is used in breast ultrasound imaging.Firstly,based on the radiated sound field characteristics of point source and rectangular source,the formula of sound pressure value at any point in the sound field of ring array ultrasonic transducer is derived,which provides theoretical basis for subsequent ring array ultrasonic imaging work.In addition,a composite signal processing method based on breast ultrasound imaging is proposed.This method is divided into two parts:radio frequency(RF)signal processing before imaging and image processing after imaging.According to the internal functions of each part,RF signal processing can be divided into filtering in frequency,time gain compensation,envelope detection,logarithmic compression and scan conversion,and image processing can be divided into median filter denoising and wavelet transform denoising.Compared with direct imaging after data processing,this method can make target information more prominent and further improve the quality of ultrasonic imaging.(2)To solve the problems of weak echo signal due to the complex anatomy of the breast and the small size of its tissues,a method of breast ultrasonic imaging based on multi-element synthetic aperture focusing(M-SAF)technology was proposed.This method uses small aperture physical elements to synthesize virtual large aperture to enhance the energy of emitted sound field and solve the problem of weak signal,so as to improve the quality of breast ultrasound imaging,which is verified by simulation data and experimental data.Firstly,1024 and 256 ring arrays are used for modeling and simulation.The results show that there are optimal sub-aperture elements in the ring arrays,and the same phenomenon of different ring arrays indicates that the results are more scientific.Secondly,nylon rope and breast phantom ultrasonic imaging were performed based on 256 ring array.The experimental results show that the optimum number of sub-aperture elements in 256 ring array is 4,and the quality of ultrasonic imaging results is the highest.(3)In order to reduce the dependence of high-quality breast ultrasound imaging on huge data,a breast ultrasound imaging method based on compressed sensing technology was proposed.This method breaks through the restriction of Nyquist-Shannon sampling theorem and indicates that if there is a high-dimensional compressible signal(a sparse transformation domain),the signal can be projected into low-dimensional space through the observation matrix(not related to the transformation basis),and a small amount of projection can reconstruct the original signal by solving the optimization problem.This can not only greatly compress the amount of data collected,but also reduce the reuse rate of the elements,so as to achieve the purpose of energy saving and loss.Experimental results show that even with only 50% of the sampled data,high-quality results can still be reconstructed.