Research And Implementation On B-mode Blood Flow Imaging Via High Frequency Ultrasound

Medical Medical ultrasound imaging systems are widely used with the advantages of non-invasive, safe, effective and real-time imaging. Also, blood flow imaging as one of the important technology in ultrasound imaging, providing reliable information for clinical diagnosis and B-mode blood flow imaging has great value for researching for its higher resolution and angle independence.This paper presents a new method for realizing the gray-scale imaging of blood flow via the high frequency ultrasound, which overcomes the shortcomings of the traditional technology such as complex, parameter dependence and non-applicable in high frequency ultrasound. Then we set up a theoretical framework which is important for the high-frequency blood flow imaging field. Firstly we analyzing the backscatter of red blood cells for high frequency ultrasound and established a comprehensive scattering model to determine the feasibility and the imaging frequency range of the blood flow imaging; then we theoretically designed the transmitting and receiving manner of the ultrasonic pulses, obtained blood flow information based on the difference between the tissue and blood flow, thus separating the weak blood echo zone and the strong tissue echo zone, and achieving the blood flow imaging under gray-scale conditions.The The project was designed based on field programmable gate array(FPGA), verified the correctness of the theoretical model and got the available frequency range. The experiments used 20MHz ultrasound probe, simulated the human blood, human blood vessels, and obtained the blood flow imaging similar to the actual results, which could distinguish the blood flow within the 0.3mm blood vessel. The image brightness was found to be related with the blood flow velocity; the linearity was better at the velocity of 7.4cm/s to 44.5cm/s, and the brightness was reached the highest level at the velocity of 51.9cm/s at. Finally we used this method to establish the venous imaging in the back of the hand, and thus got a clear intra-vascular ultrasound rheogram.By using high frequency ultrasound to detect the superficial blood vessel, abundant of blood flow signals can be obtained even using single pulse emitting. The satisfied blood flow backscatted signals can be obtained and achieve the same high resolution structural imaging, and provided a reliable reference for the diagnosis of the superficial organs.