高频超声成像中的编码激励研究

本论文实现了基于编码激励的高频超声成像实验系统并对编码激励在实际应用中的性质进行了定量实验研究.以中心频率为10 MHz的眼科B超为实验平台,实现了一个适用于各种二进制编码激励的超声成像系统.系统使用FPGA实现了编码激励实时成像处理,并通过数据采集卡获得射频回波数据.实验表明,采用编码激励可以显著增加系统信噪比,降低发射电压.在单反射面情况下,15 V发射电压的编码激励回波的信噪比与70 V发射电压的单脉冲激励回波的信噪比相当,脉冲压缩的旁瓣水平在-30 dB以下.在超声体模实验中,20 V发射电压的编码激励回波的信噪比水平及穿透深度与60 V发射电压的单脉冲激励系统相当.编码激励实验结果为实现低发射电压的便携式超声诊断系统提供了实验基础.

Study of coded excitation in high frequency ultrasound imaging

An experimental system of high frequency ultrasound imaging using coded excitation is implemented, and the quantitative study of practical applications for coded excitation is performed. Based on a 10MHz ophthalmic ultrasound imaging system, an experimental system for binary coded excitation is implemented. Real time coded excitation imaging is carried out using FPGA, and RF echo signal is acquired using data acquisition card. Experiment results show that signal to noise ratio is greatly improved using coded excitation, and excitation voltage can be reduced significantly. In the single reflector situation, the SNR of 15V-excitation-voltage coded system is comparable with that of 70V-excitation-voltage pulse excitation system, and the sidelobe level is below-30dB. In the phantom experiment, the SNR and penetration of 20V-excitation-voltage coded system are comparable with those of 60V-excitation-voltage pulse excitation system. The results give experimental support to the implementation of low excitation voltage portable ultrasound systems.