Acoustic cavitation generated by an extracorporeal shockwave lithotripter

Area of Science:

• Acoustics and Fluid Dynamics
• Biomedical Engineering
• Medical Physics

Background:

• Extracorporeal shockwave lithotripsy (ESWL) is a common procedure for kidney stone treatment.
• The precise mechanisms of tissue interaction and stone disintegration during ESWL are not fully understood.
• Acoustic cavitation is a suspected contributor to ESWL's biological effects.

Purpose of the Study:

• To provide direct evidence of acoustic cavitation generated by a Dornier extracorporeal shockwave lithotripter.
• To investigate the physical characteristics and potential impact of cavitation bubble collapse.
• To correlate observed cavitation phenomena with known biological effects of ESWL.

Main Methods:

• Utilized a Dornier extracorporeal shockwave lithotripter as the shockwave source.
• Employed various targets including x-ray film, thin aluminum sheets, and metal plates to detect cavitation effects.
• Analyzed target deformation and perforation to infer the violence of cavitation bubble collapse and associated liquid jet impacts.

Main Results:

• Observed direct evidence of acoustic cavitation generated by the lithotripter.
• Documented violent liquid jet impacts resulting from cavitation bubble collapse, capable of puncturing thin foils and deforming metal plates.
• Demonstrated that these cavitation events occurred over a significant volume (greater than 200 cm3).

Conclusions:

• The study confirms that extracorporeal shockwave lithotripsy generates significant acoustic cavitation.
• The observed liquid jet impacts are sufficiently violent to cause physical damage, suggesting a primary mechanism for ESWL's effects.
• It is highly probable that similar cavitation damage occurs in biological tissues, contributing to renal calculus disintegration and potential tissue trauma.