流动微泡群瞬态空化强度时域分布的比例反馈调节*

声波、血流环境及流动微泡群的稳定性都会影响焦区内瞬态空化强度(ICI)在超声作用时间内的分布，从而影响基于瞬态空化的治疗效率和生物安全性。本文在搭建仿体中流动微泡群瞬态空化发生和实时测量系统的基础上，设计了基于LabView FPGA的比例反馈控制器，在保持脉冲重复频率和脉冲长度不变的条件下，通过选择适当的比例系数，依据当前周期的声波激励下实时测量的ICI，实时调节下一周期声波信号的峰值负压，以调控ICI在时间上的分布。研究表明，在最优比例系数(1 × 107)下，和开环系统相比，ICI的稳定率提升~2.31 倍，ICI的时域下降速率减小~94.41%；在超声作用时间内总ICI也基本达到期望水平。这些结果表明该比例反馈控制器在调控脉冲超声激励下流动微泡群ICI时域分布的有效性，有望改进瞬态空化在相关疾病治疗中的效率和安全性。

Time domain distribution regulation of inertial cavitation intensity of flowing microbubbles based on proportional feedback controller

Acoustic pulse excitation, the blood flow environment and the stability of the microbubbles have influence on the distribution of inertial cavitation intensity(ICI) within the focal region during the exposure time, thus affecting the efficacy and biosafety of inertial cavitation-based therapy. Based on a real-time measurement system of inertial cavitation of the flowing microbubbles in tissue-mimicking phantom, a proportional feedback controller based on LabView FPGA was designed to regulate the temporal distribution of ICI. Under the condition of maintaining pulse repetition frequency and pulse length unchanged, via the optimal proportional coefficients, the amplitude of the next acoustic pulse (corresponding to the peak negative pressure) was real-time regulated by the measured ICI elicited by the present acoustic pulse. The results show that when using an optimal proportional coefficient (1 × 107), the stability rate of ICI was ~2.31 times that of open-loop system, the decreasing rate of ICI in time domain was ~94.41% of open-loop system, and the total ICI reached the desired level within the ultrasound exposure time. These results show the effectiveness of the presented controller in regulating the temporal distribution of ICI of the flowing microbubbles, and provide a promising method for improving the efficiency and safety of cavitation-based therapy.