Study And Implementation Of A Number Of New Medical Ultrasound Imaging Technology

The ultrasound imaging system is low-cost and injury free. And it is one of the most important imaging systems. But its image quality is poor, especially comparing with other imaging system.In order to improve the image quality, some new technology and new method are used in the ultrasound imaging system. The paper has some research in several aspects to improve the image quality.The coded excitation was used to the Color Flow Map (CFM) imaging in the thesis. Conventional CFM imaging needs to generate several (4-16) pulses for each velocity estimate. Thus the frame rate is seriously decreased. To circumvent the problem, A new method using coded excitation was proposed which used a broad band coded signal as excitation instead of a narrow band pulse in conventional CFM imaging. The received signal was divided into a number of narrow band signals which were also separated in time domain by filtering with a number of band filters and matched filters. Then an improved autocorrelation approach was applied on the several narrow band signals to obtain the flow velocity estimate. Finally, All the velocity estimates from each narrow band were averaged to obtain an improved velocity estimate. As each excitation lead to an estimated value of the velocity, This new method substantially increases the frame rate of CFM imaging. The thesis derived the theoretical formula which can be used in improving CFM imaging's frame rate for the first time.This thesis also carries out research on ultrasonic wave aberration of tissue harmonic imaging (THI). Whether tissue harmonic imaging can eliminate the aberration is still controversial.The result of the simulation validate the theory of Bjorn Agelsen, That THI doesn't solve the problem of ultrasonic wave aberration. And then an iterative method to reduce the ultrasound aberration was proposed. First, One transmit-beam iteration is defined as consisting of an estimation of arrival-time and amplitude fluctuations; Then these estimates were applied to a transmit-beam in order to obtain a corrected transmit-beam profile; And finally, Receiving scattering generated by the corrected transmit-beam. Such processes were repeated several times. Results show that only a few iterations are needed to obtain a corrected transmit-beam profiles comparable to those of ideal transmit-beam profiles without aberration.Finally, The design of all-digital ultrasound imaging system was given. Many modules' simulation was accomplished, such as dynamic focusing module, apodization module, aperture module, dynamic filter module, excitation module. The calculation method of every module's parameters and the concrete realization of the hardware structure were also given. It is not only the theoretical basis of the digital ultrasound imaging system, but also the complete utilitarian design. Dynamic focusing, dynamic apodization, dynamic aperture, dynamic filter, median filter, and digital scan conversion were accomplished in the all-digital ultrasound imaging system. Its image quality arrives the same level with abroad analogous.