School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0405, USA.
J Acoust Soc Am. 2011 Sep;130(3):1735-47. doi: 10.1121/1.3623749.
A technique has been developed to demodulate periodic broadband ultrasonic interrogation signals that are returned from multiple scattering sites to simultaneously determine the low-frequency displacement time histories of each individual site. The technique employs a broadband periodic transmit signal. The motions of scattering sites are separately determined from the echoed receive signal by an algorithm involving comb filtering and pulse synthesis. This algorithm permits spatial resolution comparable to pulse-echo techniques and displacement sensitivities comparable to pure-tone techniques. A system based on this technique was used to image transient audio-frequency displacements on the order of 1-10 μm peak (≥ 50 nm/√Hz) that were produced by propagating shear waves in a tissue phantom. The system used concentric transmitting and receiving transducers and a carrier signal centered at 2.5 MHz with an 800 kHz bandwidth. The system was self-noise-limited and capable of detecting motions of strongly reflecting regions on the order of 1 nm/√Hz. System performance is limited by several factors including signal selection, component hardware, and ultrasonic propagation within the media of interest.
已经开发出一种技术来解调从多个散射点返回的周期性宽带超声询问信号，以同时确定每个散射点的低频位移时间历史。该技术采用宽带周期性发射信号。通过涉及梳状滤波和脉冲合成的算法，从回波接收信号中分别确定散射点的运动。该算法允许与脉冲回波技术相当的空间分辨率和与纯音技术相当的位移灵敏度。基于该技术的系统用于对组织模拟体中传播的剪切波产生的 1-10 μm 峰（≥50nm/√Hz）量级的瞬态音频位移进行成像。该系统使用同心发射和接收换能器以及中心频率为 2.5MHz、带宽为 800kHz 的载波信号。该系统受自身噪声限制，能够检测到强反射区域的运动，其量级为 1nm/√Hz。系统性能受到多种因素的限制，包括信号选择、组件硬件以及感兴趣介质中的超声传播。
