In the aim of limiting the destructive effects of collapsing bubbles, the regime of stable cavitation activity is currently targeted for sensitive therapeutic applications such as blood-brain barrier opening by ultrasound. This activity is quantified through the emergence of the subharmonic component of the fundamental frequency. Due to the intrinsically stochastic behavior of the cavitation phenomenon, a better control of the different (stable or inertial) cavitation regimes is a key requirement in the understanding of the mechanisms involving each bubble-induced mechanical effect. Current strategies applied to stable cavitation control rely on the use of either seeded microbubbles or a long-lasting pulse to reinitiate subharmonic emission. The present work aims at developing an ultrafast (inferior to 250μs$250\mu s$) monitoring and control of subharmonic emissions during long-pulsed (50 ms) sonication. The use of a FPGA-based feedback loop provides reproducibile level of subharmonic emissions combined with temporal stability during the sonication duration. In addition, stable cavitation events are differentiated from the broadband noise characterizing inertial cavitation activity, with perspectives in the discrimination of the involved mechanisms underlying bubble-mediated therapeutic applications.

为了限制破裂的气泡的破坏作用，稳定的气蚀活性方案目前针对敏感的治疗应用，例如通过超声打开血脑屏障。通过基频次谐波分量的出现可以量化这种活动。由于空化现象的内在随机行为，对不同（稳定或惯性）空化状态的更好控制是理解涉及每个气泡引起的机械效应的机制的关键要求。用于稳定气穴控制的当前策略依赖于使用播种的微气泡或长脉冲来重新启动次谐波发射。目前的工作旨在开发超快（低于250μs的$250\mu s$）在长脉冲（50 ms）超声处理过程中监视和控制次谐波发射。基于FPGA的反馈回路的使用可提供可再现的亚谐波发射水平，并在超声处理期间具有时间稳定性。此外，稳定的空化事件与表征惯性空化活动的宽带噪声有所区别，并具有辨别涉及气泡介导的治疗应用的相关机制的观点。