一种基于FPGA的高频超声灰阶血流成像系统设计

摘要

目的:研制一套基于现场可编程门阵列(field-programmable gate array,FPGA)的高频超声灰阶血流成像系统,实现浅表器官血流和组织的同时实时成像.方法:该系统主要由超声换能器、超声发射接收模块、上位机成像软件和外围设备组成.超声换能器采用20～50 MHz单阵元聚偏氟乙烯(polyvinylidene fluoride,PVDF)换能器;超声发射接收模块采用高速模数转换器(analog to digital converter,ADC)直接将射频回波信号提前数字化,再由FPGA对数字信号进行多次发射叠加、滤波、检波、对数放大及二次采样等处理,并由USB接口传输至上位机进行实时显示.结果:使用该系统对人手背部静脉距表皮1 mm的血管进行超声扫描检查,可得到各种发射频率对应的血流结果图像.结论:该系统实现了浅表器官血流的实时成像,方案结构简洁清晰,为高频超声灰阶血流成像奠定了实验基础.%Objective To develop a set of high-frequency ultrasound grayscale blood flow imaging system based on field programmable gate array (FPGA) to execute simultaneous imaging of superficial blood flow and tissues.Methods This system was mainly composed of an ultrasonic transducer,an ultrasonic transmission and receiving modules,imaging software in host computer and peripheral equipment.A PVDF transducer with the frequency between 20 and 50 MHz was used for the ultrasonic transducer.In transmission and receiving modules,the radio frequency echo signals were digitized by high-speed A/D.Then the digital signals were transmitted,added,filtered,demodulated,log amplified,double sampled,and lastly transferred to the host computer by USB interface for real-time display.Results A vascular 1 mm far form the surface of the hand skin was examined by this system.Four blood flow images were obtained in corresponding with four transmission frequencies.Conclusion Real-time superficial organ blood flow imaging is realized by this system.The solution has the architecture concise and clear,and lays an experimental foundationfor high-frequency ultrasound gray-scale blood flow imaging.