Ultra-fast Ultrasound Vector Blood Imaging Technology Based On Plane-wave

Medical ultrasound blood flow imaging system becomes an important reference, while diagnosing the cardiovascular disease. Conventional ultrasound Doppler flow imaging system uses focused ultrasound to scan line by line, which leads to very low imaging frame rate, usually around a dozen frames. Luckily, plane wave method overcome this drawback and enhance the framerate, so that one can observe some special phenomenon when blood flow very fast. Vector flow imaging technology could express both the scale and direction of flow velocity. Therefore, this article mainly investigates plane wave ultra-fast vector flow imaging method, together with critical technology relatively.First of all, this thesis describes the basic theory of ultrasound vector imaging in detail. Then plane wave Doppler flow imaging was introduced. In order to analysis the resolution, contrast, Signal to Noise Ratio, flow velocity estimation and frame rate, simulation experiment was executed. The results show that compound plane wave imaging could keep the uniform imaging quality and accuracy of velocity estimation compared to focused imaging method. Moreover, compound plane wave can provide very high frame rate (5 plane wave,10 kHz pulse repletion frequency, around 2000fps).Secondly, Because of the limitation of the order when designing wall filter on traditional Doppler system, the image quality decreases. However, plane wave method does not have this defects. This paper designed phantom experiment to compare performance of IIR, FIR and polynomial regression wall filter on plane wave flow imaging system. The results show that FIR wall filter is the best choice in practical application.Finally, a new high frame-rate two-dimensional vector flow imaging method was described in order to overcome the lack of imaging frames and directional information on traditional ultrasound flow imaging. The method combined the plane wave imaging technology, multi-synthetic aperture method,2-D auto-correlation method and compound imaging technology. The beamforming steering was achieved only in the receiving mode on two independent subapertures, left and right respectively. Ultimately, horizontal and axial flow velocity were obtained. Its effectiveness was verified through the Field II simulation experiments, vitro- and vivo-experiments. Simulation results show that the bias of axial velocity is around 0.035m/s and the standard variance is about 0.0013m/s; at the same time, that of horizontal estimates achieves about 0.08m/s and 0.009m/s respectively. Compared with the recent published method, the horizontal estimate bias decreases 0.02m/s, and axial estimate bias decreases 0.003m/s. The stability of the estimates are extremely enhanced by tilting the emitting plane wave at each transmission and compound processing. Finally, the design of vitro- and vivo- experiments prove that this method has application prospect.