Xu Xiaochen, Sun Lei, Cannata Jonathan M, Yen Jesse T, Shung K Kirk
NIH Resource on Medical Ultrasonic Transducer Technology, Department of Biomedical Engineering, University of Southern California, Los Angeles, CA 90089, USA.
Ultrasound Med Biol. 2008 Apr;34(4):638-46. doi: 10.1016/j.ultrasmedbio.2007.09.012. Epub 2007 Nov 12.
In this paper, we report the development of the first high-frequency (HF) pulsed-wave Doppler system using a 30-MHz linear array transducer to assess the cardiovascular functions in small animals. This array-based pulsed-wave Doppler system included a 16-channel HF analog beamformer, a HF pulsed-wave Doppler module, timing circuits, HF bipolar pulsers and analog front ends. The beamformed echoes acquired by the 16-channel analog beamformer were fed directly to the HF pulsed-wave Doppler module. Then the in-phase and quadrature-phase (IQ) audio Doppler signals were digitized by either a sound card or a Gage digitizer and stored in a personal computer. The Doppler spectrogram was displayed on a personal computer in real time. The two-way beamwidths were determined to be 160 microm to 320 microm when the array was electronically focused at different focal points at depths from 5 to 10 mm. A micro-flow phantom, consisting of a polyimide tube with an inner diameter of 127 microm and the wire phantom were used to evaluate and calibrate the system. The results show that the system is capable of detecting motion velocity of the wire phantom as low as 0.1 mm/s, and detecting blood-mimicking flow velocity in the 127-microm tube lower than 7 mm/s. The system was subsequently used to measure the blood flow in vivo in two mouse abdominal superficial vessels, with diameters of approximately 200 microm, and a mouse aorta close to the heart. These results demonstrated that this system may become an indispensable part of the current HF array-based imaging systems for small animal studies.
在本文中，我们报告了首个使用30兆赫线性阵列换能器来评估小动物心血管功能的高频（HF）脉冲波多普勒系统的研发情况。这个基于阵列的脉冲波多普勒系统包括一个16通道高频模拟波束形成器、一个高频脉冲波多普勒模块、定时电路、高频双极脉冲发生器和模拟前端。由16通道模拟波束形成器采集的波束形成回波被直接馈送到高频脉冲波多普勒模块。然后，同相和正交（IQ）音频多普勒信号通过声卡或盖奇数字转换器进行数字化，并存储在个人计算机中。多普勒频谱图实时显示在个人计算机上。当阵列在5至10毫米深度的不同焦点处进行电子聚焦时，双向波束宽度确定为160微米至320微米。使用一个由内径为127微米的聚酰亚胺管组成的微流模型和线模型来评估和校准该系统。结果表明，该系统能够检测低至0.1毫米/秒的线模型运动速度，并能检测内径127微米的管内模拟血流速度低于7毫米/秒。该系统随后被用于测量两只小鼠腹部直径约为200微米的浅表血管以及靠近心脏的小鼠主动脉中的体内血流。这些结果表明，该系统可能会成为当前用于小动物研究的基于高频阵列的成像系统中不可或缺的一部分。
