Cavitation-induced streaming in shock wave lithotripsy.

Area of Science:

• Acoustics
• Fluid Dynamics
• Biomedical Engineering

Background:

• Cavitation is a critical phenomenon in lithotripsy.
• Understanding bubble dynamics is essential for optimizing shock wave lithotripsy (SWL).

Purpose of the Study:

• To investigate cavitation dynamics induced by lithotripter shock waves.
• To analyze the effect of pulse repetition frequency (PRF) and power level (PL) on cavitation.
• To characterize microbubble migration patterns.

Main Methods:

• Utilized a Dornier DoLi-50 electromagnetic lithotripter to generate shock waves.
• Employed a 60 frames-per-second camcorder to record microbubble migration in non-degassed water.
• Varied the PRF (0.5 and 2 Hz) and power level (PL) of the lithotripter.

Main Results:

• Cavitation dynamics were significantly influenced by PRF and PL.
• At lower PRF, cavitation was sparse and bubbles moved with shock wave propagation.
• Higher PRF led to bubble cloud amplification and opposite-direction streaming.
• Increased PL expanded the cavitation field and enhanced opposing bubble flow.

Conclusions:

• Shock wave parameters critically control cavitation behavior and bubble streaming.
• The observed bubble dynamics provide insights into acoustic streaming effects in SWL.
• Findings can inform the design and application of lithotripters for improved stone fragmentation.