调频激励增强微气泡的次谐波理论和实验研究

超声造影剂的次谐波成像可以提高造影组织比，提供更好的图像质量. 提出一种利用调频脉冲激励以增强造影剂微气泡产生的次谐波新方法. 基于修正的Church方程，从理论上讨论了次谐波的产生与调频激励声压的关系及产生阈值，并且实验证实了优化调频信号的带宽及调频时间可以提高次谐波信号幅度及改善主瓣和旁瓣特性. 理论与实验表明，与传统脉冲信号激励相比，调频信号激励产生的次谐波幅度可提高约22dB. 关键词： 调频激励 超声造影剂 微气泡 次谐波

Theoretical and experimental study of enhanced subharmonic emission from microbubbles with chirp excitation

Subharmonic contrast imaging provides improved ultrasound imaging quality by taking advantage of increased contrast to tissue ratio. This article presents a novl approach to enhance the subharmonic emission from microbubbles by using a chip excitation technique. The chirp excitation pressure threshold and the sound pessure dependence of subharmonic are theoretically evaluated based on the Churc's model. Measurements validate that the optimized bandwidth and time duration of the chirp excitation can improve subharmonic amplitude and reduce side-lobe level. Both theoretical and experimental results demonstrate that the chirp excitation can improve the amplitude up to 22dB over the pulse excitation at the subharmonic frequency when comparing the coded excitation with traditional pulse excitation.