Reduction of bubble cavitation by modifying the diffraction wave from a lithotripter aperture

Area of Science:

• Biomedical Engineering
• Acoustic Physics
• Nephrology

Background:

• Shockwave lithotripsy (SWL) is a common procedure for kidney stone removal.
• Bubble cavitation during SWL can cause collateral tissue damage, particularly to the renal parenchyma.
• Reducing cavitation is crucial for improving SWL safety and patient outcomes.

Purpose of the Study:

• To develop and evaluate a novel method for suppressing bubble cavitation in the focal zone of an electrohydraulic lithotripter.
• To mitigate shockwave-induced renal injury by controlling cavitation.

Main Methods:

• An edge extender was designed and attached to an electrohydraulic lithotripter's ellipsoidal reflector.
• The extender was intended to modify diffraction waves at the aperture without altering the acoustic field within the reflector.
• Bubble cavitation suppression was assessed using passive cavitation detection and blood vessel phantom rupture tests.

Main Results:

• The edge extender significantly shortened the duration of the tensile wave at the lithotripter focus.
• Bubble cavitation was effectively suppressed, as evidenced by longer bubble collapse times.
• Blood vessel phantom rupture required 300 shocks with the extender versus only 30 shocks with the original configuration.
• Stone comminution efficiency with the extender was comparable to the original lithotripter.

Conclusions:

• Modifying diffraction waves at the lithotripter aperture is an effective strategy to suppress bubble cavitation.
• This approach significantly reduces the damage potential of SWL on surrounding tissues.
• The developed method offers a promising way to enhance the safety of lithotripsy without compromising stone fragmentation efficacy.