The effect of polypropylene vials on lithotripter shock waves

Area of Science:

• Biophysics
• Acoustics
• Nephrology

Background:

• Shock wave lithotripsy (SWL) is a common treatment for kidney stones.
• Understanding SWL mechanisms is crucial for improving treatment efficacy and minimizing cell injury.
• Previous studies have not fully explored the influence of experimental setup geometry on SWL outcomes.

Purpose of the Study:

• To investigate the effect of specimen vial shape on shock wave (SW) propagation and kidney cell injury during SWL.
• To quantify acoustic field differences within vials of varying shapes.
• To determine the role of vial geometry in SWL-induced cellular damage.

Main Methods:

• Kidney cells were treated with SWs in a Dornier HM3 lithotripter using polypropylene vials with flat and round ends.
• Acoustic fields within vials were measured using both lithotripter SWs and pulsed ultrasound (US).
• Pressure amplitudes and spatial pressure distributions were analyzed for both vial types.

Main Results:

• Lytic injury to kidney cells was significantly higher (p < 0.0001) when SWs entered through the flat end of the vial.
• The average peak positive pressure inside the flat vial was double that of the round vial.
• Ultrasound experiments revealed sound field focusing induced by the round vial's curved interface, creating acoustic 'hot spots' and 'cold spots'.

Conclusions:

• The shape of the specimen vial is a critical factor influencing the acoustic field and cell injury during SWL.
• Flat-ended vials result in higher peak pressures and greater cell injury compared to round-ended vials.
• These findings underscore the need to consider vial geometry in SWL modeling and experimental design to ensure accurate and reproducible results.