Scattering from red blood cells (blood noise) increases significantly as the ultrasound frequency is increased above 10 MHz. This reduces the contrast between the vessel wall and the lumen in intravascular ultrasound imaging which makes it difficult to localize the vessel wall and plaque. A blood noise filter based on beam tilting and digital lateral low pass filtering is described. Beam tilting introduces a Doppler shift from blood which results in a frequency separation of the vessel wall signal and the blood noise. The performance of the filter is investigated by simulations and by in vitro experiments. The filter is found to be effective for blood velocities exceeding approximately 50 cm s/sup -1/ at a 20 MHz ultrasound frequency with a beam tilt angle of 10 degrees and a frame rate of 15 f.p.s. By increasing the system frequency to 40 MHz, increase the beam tilt angle to 15 degrees and reduce the frame rate to 10 f.p.s., the filter is effective for blood velocities below 10 cm s/sup -1/.
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机译：随着超声频率增加到10 MHz以上，来自红细胞的散射（血液噪声）显着增加。这降低了血管内超声成像中血管壁和管腔之间的对比度，这使得难以定位血管壁和斑块。描述了基于波束倾斜和数字横向低通滤波的血液噪声滤波器。光束倾斜会引起血液中的多普勒频移，从而导致血管壁信号和血液噪声的频率分离。通过模拟和体外实验研究了过滤器的性能。发现该过滤器对于在20MHz的超声波频率下具有超过50cm s / sup -1的血流速度是有效的，其束倾斜角为10度并且帧速率为15f.p.s。通过将系统频率增加到40 MHz，将光束倾斜角增加到15度，并将帧频降低到10 f.p.s.，该滤镜对于低于10 cm s / sup -1 /的血流速度是有效的。
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