Blood flow image by multi-angle composite ultrasonic Doppler vector

Abstract

Precise measurement of blood flow is of vital importance in studying the formation of thrombus and atherosclerotic plaque. However, conventional color Doppler methods are limited to obtaining the velocity component along the ultrasound beam and have poor accuracy. Several Doppler flow imaging methods based on the plane wave emission can estimate the blood velocity vectors and visualize hemodynamic parameters, which provide more detailed blood flow information and effectively improve the capability of clinical diagnosis treatment. Considering the low accuracy of the Doppler flow methods for measuring velocity in complex flow fields, an optimization technique is used to improve the imaging quality and the accuracy of velocity estimation. In this study we propose a modified vector Doppler method through combining multi-angle compound technique, to reconstruct blood velocity vectors of carotid bifurcations obtained from 3D printing. Since the multi-angle compound technology can effectively improve the quality of imaging, this technology is applied to Doppler imaging to achieve high-accuracy velocity estimation. It can significantly reduce the velocity estimation errors. Comparing the velocity estimation accuracy of different angle compound numbers (<i>n</i> = 1, 3, 5, and 7) in the simulation, it is found that the accuracy of velocity estimation increases with angle compound increasing. Beside, the 5-angle compound method is more robust for velocity estimation and can obtain higher frames. The experiments were carried out using a programmable ultrasonic array system and a high-frequency linear array transducer L12-5c with a central frequency of 8.125 MHz. The sample rate is set to be 31.25 MHz. The imaging results of carotid bifurcation also show that the vector Doppler based on 5-angle compound can obtain a clear image of intravascular vector flow, which is beneficial to the identifying of complex flow state, and realize intravascular dynamic imaging. Especially, it can capture the vortex phenomenon in the blood stream. The quantitative results indicate that this method significantly reduces the error between the flow calculation results and the reference results, making the estimation results more accurate. In conclusion, the vector Doppler method based on multi-angle compound has the good performance of visualizing complex blood flow and calculating hemodynamic parameters. It also provides the reference for the diagnosis of cardiovascular disease and the research of flow imaging methods.