Cloud cavitation control for lithotripsy using high intensity focused ultrasound

Area of Science:

• Acoustics
• Biomedical Engineering
• Medical Physics

Background:

• Cloud cavitation, a destructive phenomenon, can generate high pressures upon collapse.
• Controlling cloud cavitation is crucial for therapeutic applications like kidney stone treatment.

Purpose of the Study:

• To investigate a novel two-frequency ultrasound waveform for controlled cloud cavitation collapse.
• To assess the efficacy of this method for fragmenting kidney stones in vitro.

Main Methods:

• Utilized a high-frequency pulse (1-4 MHz) to induce cloud cavitation and a low-frequency pulse (545 kHz) to trigger its collapse.
• Employed high-speed photography, shadowgraphy, and hydrophone measurements to observe cavitation dynamics.
• Conducted in vitro erosion tests on model and natural kidney stones.

Main Results:

• High-frequency ultrasound localized cloud cavitation near a surface.
• The two-frequency cavitation control (C-C) waveform successfully induced shock waves.
• The C-C waveform demonstrated superior stone erosion rates compared to single frequencies.
• Natural stones were eroded into fragments predominantly smaller than 1 mm.

Conclusions:

• The developed C-C waveform effectively controls cloud cavitation for potential lithotripsy.
• Further optimization of ultrasound parameters and in vivo studies are warranted for clinical application.