调频超声激励造影剂微气泡的次谐波响应研究

Sub-harmonic response from microbubble population under ultrasound chirp excitation

目的 研究利用调频超声激励微气泡群产生的次谐波进行血压测量的有效性。方法 选用参数相同的调频波和正弦波,通过模拟计算和实验研究比较两种激励下次谐波的幅度与激励声压之间的关系,分析次谐波幅度对过压变化的敏感度;同时探讨调频波的带宽和循环数对次谐波幅度所产生的影响。结果 调频波可以提高次谐波的幅度5~10dB,过压测量的敏感度提高3.4dB。结论适当地增大调频信号的带宽或循环数,可以提高次谐波对过压的敏感程度。

Objective To investigate the effectiveness of noninvasive blood pressure measurement by detecting the sub- harmonic response excited by chirp ultrasound scattered from microbubbles. Methods The dependence of sub-harmonic re- sponse respectively on exciting acoustic pressure and ambient pressure while utilizing chirp excitation was investigated, and comparisons were made between the results of chirp and traditional sinuous pulse. Then, in order to optimize the parame- ters of chirp signal, the effect of chirp bandwidth and pulse length on the variation sub-harmonic component were dis- cussed. Results As a superior excitation, chirp ultrasound greatly enhanced the amplitude of sub-harmonic component of 5--10 dB and its sensitivity of 3.4 dB to the ambient pressure. Conclusion In order to optimize the sensitivity of pressure measurement by chirp excitation, a wider frequency range and a longer pulse length can be utilized to increase the reduction when ambient pressure increases