调频超声脉冲驱动微气泡运动偏移的研究

提出调频超声辐射力技术驱动微泡群，以加强微泡的吸附效率.基于改进的RP方程及粒子轨迹方程研究了微泡群整体的运动位移与调频信号的中心频率、调频范围、信号声压，以及微泡半径分布关系.研究结果表明调频信号在驱动半径具有宽泛分布的气泡群，以及半径分布远离谐振半径的气泡群时，作用效果好于传统正弦波信号.例如中心频率1 MHz、调频范围0.75 MHz的调频脉冲作用高斯分布（平均半径3.5 μm、均方差为1）的微泡群200 μs，可比同等声压的正弦波多约12%的微气泡产生位移30 μm. 关键词： 超声辐射力 调频波 高斯分布

Microbubble displacement under ultrasonic chirp excitation

Ultrasound radiation force has been shown promising in facilitating ultrasonic molecular imaging and target drug delivery. A chirp excitation technique is developed to improve the translational displacement of microbubbles in this study. Based on a modified RP equation and a particle trajectory equation, we investigate the dependence of the translation of microbubble clouds on the chirp parameters （center frequency and frequency shift） and bubble radius distribution. Results demonstrate that the chirp excitation performs better than the traditional sinusoidal excitation in displacing widely distributed microbubbles and bubble clouds with radius far from resonant size. For example, for Gaussian size-distributed microbubble clouds with mean radius 3.5 μm and variance of 1, a 1 MHz center frequency chirp with frequency range 0.75 MHz induces about 12% more microbubbles displaced over a distance of 30 μm during 200 μs insonification, compared with a 1 MHz sinusoidal excitation with equal acoustic pressure.