Study On Key Technologies Of Elasticity Imaging Based On Acoustic Radiation Force

To achieve the non-contact detection for the elastic properties of viscoelastic material in a low SNR environment, a kind of elasticity imaging technique based on acoustic radiation force was proposed in this dissertation by using acoustic radiation force as the driving force source to non-contactly act on the tested viscoelastic material and time delay estimator to process the ultrasonic echo signals. On the basis of establishing the theoretical model of acoustic radiation force and analyzing its impact factors, an ultrasonic flexible transmitter module was developed to effectively control the acoustic radiation force by using CPLD as the central control unit. Meanwhile, the maximum likelihood correlation time delay estimator technique was used to process the ultrasound echo signals to resolve the low resolution problem of the traditional time delay estimator algorithm in the low SNR environment. In addition, the idea of parallel processing was adopted to study on the real-time elasticity imaging technique based on the acoustic radiation force by using FPGA as the central processing unit. On these bases, an experimental platform used for the elasticity imaging based on acoustic radiation force was developed, and the platform was used to carry out the experimental study to validate the feasibility and effectiveness of the proposed methods in this dissertation. The detail contents of this dissertation are presented as below:Chapter 1, a survey of the importance of research on the elasticity imaging technology based on acoustic radiation force was given and the review of current research status and future developing trend of elasticity imaging and its key technology were summarized. Then the research content of this dissertation was presented and each chapter of this dissertation was arranged.Chapter 2, on basis of establishing the theoretical model of acoustic radiation force and analyzing its impact factors, an ultrasound flexible transmitter module was developed by using CPLD as the central control unit, which can effectively control the acoustic radiation force by adjusting related parameters of the exciting pulse.Chapter 3, on the basis of establishing the ultrasound echo model and determining the performance evaluation criteria of time delay estimators, a kind of maximum likelihood correlation time delay estimator technology was proposed to realize the multi-resolution deformation detection of the tested materials, and resolve the low resolution problem of the traditional time delay estimator algorithm in the low SNR environment.Chapter 4, in order to solve the drawback of the current traditional elasticity imaging technology based on acoustic radiation force that it is difficult to achieve the real-time detection of tested materials, the idea of parallel processing was adopted to carry out the preliminary study on the real-time processing system of ultrasound echo signals by using FPGA as the central processing unit. The study provides a solid foundation for a further research on the real-time elasticity imaging technology based on ultrasound radiation force.Chapter 5, based on designing the experimental system general scheme, developing a kind of ultrasonic echo conditioning module with high signal to noise ratio performance, and combining with the ultrasound flexible transmitter module in chapter 2, an experimental platform used for the acoustic radiation force elasticity imaging was integrated. Then, biological tissues were used as the tested objects to carry out the experimental research by means of this platform, and the results validated the feasibility and effectiveness of the technique proposed in this dissertation.Chapter 6, as the last chapter, the main work and conclusions in this dissertation were summarized and the prospect for further research objects was put forward.