Stone geometry and structure dependence on extracorporeal shock wave lithotripsy

Area of Science:

• Geophysics
• Materials Science
• Biomedical Engineering

Background:

• Understanding shock wave lithotripsy (SWL) fragmentation is crucial for treating kidney stones.
• The Siemens Lithostar device utilizes electromagnetic shock waves for stone disintegration.
• Previous studies have not fully elucidated the impact of shock wave energy and angle on fragmentation efficiency, especially for irregular calculi.

Purpose of the Study:

• To investigate the in vitro fragmentation effects of electromagnetic-induced shock wave lithotripsy on laminated schists.
• To analyze the influence of incoming shock wave energy and incident angle on fragmentation.
• To determine the implications for treating irregularly shaped calculi, such as staghorn stones.

Main Methods:

• In vitro experiments using parallel laminated schists as a model stone material.
• Controlled application of electromagnetic-induced shock waves from a Siemens Lithostar device.
• Systematic variation of incoming shock wave energy and incident angles.

Main Results:

• Above a threshold energy level, the total acoustic energy required for fragmentation was independent of the power setting.
• Total reflection angles significantly limited the energy transmitted to the stone, reducing the effective transmission surface.
• Cavitation induced by lithotripsy was observed but did not immediately contribute to stone disintegration.

Conclusions:

• Shock wave energy transmission and fragmentation efficiency are significantly influenced by the incident angle due to total reflection.
• These findings have direct implications for the effectiveness of SWL on irregularly shaped calculi like staghorn stones.
• Further research is needed to understand the role of lithotripsy-induced cavitation in stone fragmentation.