Air pockets trapped during routine coupling in dry head lithotripsy can significantly decrease the delivery of shock...

Area of Science:

• Biomedical Engineering
• Acoustic Physics

Background:

• Current lithotriptors require coupling agents like gel or oil for dry treatment heads.
• The efficiency of shock wave energy delivery is critical for effective stone fragmentation.

Purpose of the Study:

• To investigate the impact of coupling quality on stone breakage during simulated lithotripsy treatments.
• To quantify the effect of air pockets at the coupling interface on shock wave transmission.

Main Methods:

• Utilized a Dornier electromagnetic lithotriptor with a Mylar membrane for coupling.
• Photographed air pockets at the interface to quantify coupling quality.
• Measured acoustic pressure and assessed gypsum stone breakage under various coupling conditions.

Main Results:

• Air pockets (1.5%-19% coverage) reduced shock wave amplitude by ~20%.
• Repositioning the patient decreased acoustic pressure by 32% and energy transmission by 57%.
• 2% air coverage reduced stone breakage by 20%-40%.

Conclusions:

• Coupling quality is a critical factor in lithotripsy, affecting shock wave energy delivery.
• Air pockets at the interface significantly impair stone fragmentation.
• Recoupling during patient repositioning is disruptive and can degrade treatment efficacy, potentially explaining clinical outcome variability.