基于临界角侧波原理的一种轴向传输超声骨密度仪

An ultrasound bone densitometer of axial transmission based on critical angle and lateral wave

目的为实现高便携性、高精度、高检测效率的骨密度测量,介绍了基于临界角侧波原理的轴向透射技术的原理和应用,并基于该原理设计了一种以FPGA为核心的前端超声采集单元和PC机端信号处理的检测系统。方法系统使用现场可编程门阵列(Field Programmable Gate Array,FPGA)Spartan-6(XC6SLX9)为核心,控制14 bit的AD6645以100 MHz进行高速采样,并通过USB2.0高速转换芯片FT232H进行数据传输。供电部分采用USB 5V供电并控制开关电源芯片LM3674和低压差线性电源芯片(LDO)WDY05D0505分别对数字和模拟电路供电。结果在Windows7系统下利用C#测试软件测得USB传输速率可达到40 Mb/s,每次采集数据的传输时间仅为12.5 ms。结论基于临界角侧波原理的轴向传输超声骨密度仪的高采样率和高USB传输速率可提升骨密度测量重复性与速度。

Objective In order to achieve high portability, high accuracy and high detection efficiency of bone density measurement, this paper describes the principles and applications of axial transmission technology based on critical angle and lateral wave and designs a detection system including the ultrasound signal collection using field programmable gate array （FPGA） as the core and signal processing in PC. Methods The system uses FPGA Spartan-6（XC6SLXg） as the core, the 14 bit AD6645 to control 100 MHz high-speed sampling and USB2.0 high-speed conversion chip FT232H to transfer data. USB 5 V power supplies the power and controls the switching of power supply chip LM3674 and low dropout linear power chip （LDO） WDY05D0505 to power digital and analog circuits, respectively. Results USB transmission rate of the system can reach 40 MB/s, data acquisition and transmission is only 12.5 ms each time, making the system collection efficient. Conclusions Sampling rate and USB transfer rate are the core of bone density measurement.