双频激励超声造影剂微气泡差频特性的理论和实验研究

超声参量阵效应产生的差频超声由于具有较小的衰减系数,能够有效提高传播深度而实现深层组织的超声成像. 本文基于RPNNP方程,对双频激励超声造影剂微气泡所产生差频信号声压进行了理论推导,并用Runge-Kutta算法进行了数值模拟,对差频信号产生的条件包括激励声压、超声频率和气泡大小等进行了优化,同时用不同参数的双频信号辐射造影剂实现差频超声激发的实验研究,理论与实验结果均表明当双频信号的频率差接近气泡的共振频率时可以大幅度提高差频信号的声压(28 dB),获得高信噪比的差频信号,本研究为双频超声激励下造影剂差频成像的实际应用提供了研究基础.
The ultrasound image depth can be enhanced using the Difference-frequency(DF)ultrasound generated by the parametric effect with low attenuation coefficient. In this paper,a theoretical derivation of DF signal from contrast agents with dual-frequency excitation is proposed based on the solution of the RPNNP equation,and nμmerical simulations are performed using the Runge-Kutta algorithm. The optimization of the DF generation is discussed associated with the excite pressure,frequency difference and microbubble size and the dual-frequency excitation experiments are performed for DF geration. The favorable results demonstrate that the optimized DF ultrasound can be achieved with a pressure enhancement as high as 28 dB when the difference frequency is close to the resonance frequency of the contrast agents with improved signal-to-noise ratio,which provide the basis for potential application of DF ultrasound in medical imaging