Research On Pulse Doppler Ultrasound Blood Flow Measurement Device

Ultrasound without injury to our body has high sensitivity, good reproducibility and many other advantages, which is used to measure the blood flow parameters for the target to achieve the prevention, diagnosis and treatment of cardiovascular diseases. The measurement of blood flow velocity is based on the medical ultrasound Doppler technology. By detecting the ultrasound Doppler frequency-shift signals from blood, we can see whether the blood flow is normal or not. At present, this kind of technology, with broad prospects for development and application, has been widely used at home and abroad with a lot of advantages, such as the cheaper equipment and the low Physical examination cost.Based on the Doppler effect, the speed of blood flow is detected by pulse Doppler ultrasound system, which has the ability to identify the depth of blood in one's body. By using Doppler technique combined with pulse echo technique, echo Doppler information can be obtained at the selected depth with different time delay. Blood flow measurement system consists of ultrasound emission circuit, ultrasound receiver circuit and high-speed data acquisition circuit. The disposure circuits of analog signals contain isolation and low-noise preamplifier, band-pass filter and variable gain amplifier. FPGA, as the core of this system, is used to complete the excitation pulse generator, the system timing control, echo signal amplitude extraction and data transmission tasks. Finally, the data are saved into the high-speed buffer memory in FPGA, and then are transferred to PC by USB. The Doppler frequency-shift signals at the selected depth, the spectrum and the results of blood velocities will be displayed intuitively by the interface designed by.NET.By simulation and debugging, the testing platform is correct. The experiment results show that the high-speed sampling can retain the echo information completely and the high-speed buffer memory, as a bridge between A/D and MCU, can achieve data buffer effectively, ensuring the reliability of data acquisition. FPGA used in this system, makes the design and debugging cycles reduced greatly. In addition, the hardware structure is simple and the software control is flexible. This kind of design reduces the cost and power consumption of the whole system. However, in the experiment, blood flow echo signal is so week that the impact of noise and interference is greater, therefore, further improvements are needed from both hardware and software.