Improving temporal stability of stable cavitation activity of circulating microbubbles using a closed-loop controller...

Area of Science:

• Acoustics
• Biomedical Engineering
• Therapeutic Ultrasound

Background:

• Stable cavitation (SC) using microbubbles shows therapeutic promise but requires precise control for uniformity and safety.
• Spatiotemporal distribution of SC activity impacts treatment efficacy and potential adverse effects.
• Controllable SC activity is crucial for enhanced therapeutic efficiency and biosafety.

Purpose of the Study:

• To develop and evaluate a closed-loop feedback controller for regulating stable cavitation (SC) activity.
• To improve the temporal stability of SC using pulse length (PL) regulation.
• To enhance therapeutic efficiency and biosafety by achieving controllable cavitation.

Main Methods:

• Utilized a 1 MHz focused transducer to expose microbubbles in a flowing phantom.
• Employed a 7.5 MHz plane transducer for real-time SC signal detection and high-speed acquisition.
• Implemented a closed-loop feedback controller adjusting pulse length (PL) and peak negative pressure (PNP) based on real-time SC intensity.

Main Results:

• The PL-regulated controller significantly improved the rise time and temporal stability of SC intensity.
• Optimized proportional coefficients enhanced SC intensity during acceleration and stable stages.
• The PL-based controller reduced transitions between stable and inertial cavitation, mitigating bioeffect risks.

Conclusions:

• The proposed pulse length (PL)-based closed-loop feedback controller effectively enhances stable cavitation (SC) temporal stability.
• This controller offers a feasible strategy for achieving controllable cavitation activity in therapeutic applications.
• PL regulation provides improved biosafety by minimizing the risk of unwanted inertial cavitation.