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Turbulent water coupling in shock wave lithotripsy
Jaclyn Lautz1, Georgy Sankin, Pei Zhong
1Department of Mechanical Engineering and Materials Science, Duke University, Durham, NC 27708, USA.
Physics in Medicine and Biology
|January 17, 2013
Summary
Removing cavitation nuclei with a degassed water jet significantly improved stone fragmentation in shock wave lithotripsy. This method enhances treatment efficacy by preventing energy loss from bubble proliferation.
Area of Science:
- Acoustics
- Biomedical Engineering
- Medical Physics
Background:
- Stone comminution in shock wave lithotripsy decreases with higher pulse repetition frequencies due to bubble proliferation.
- Cavitation nuclei in the acoustic coupling cushion absorb shock wave energy, reducing stone fragmentation efficiency.
- Existing lithotripsy methods are limited by the impact of cavitation bubbles.
Purpose of the Study:
- To investigate the effect of cavitation nuclei on stone comminution efficiency.
- To introduce and evaluate a method for removing cavitation nuclei from the acoustic coupling cushion.
- To enhance the efficacy of shock wave lithotripsy.
Main Methods:
- A degassed water jet was used to remove cavitation nuclei from the coupling cushion between shock wave pulses.
- B-mode ultrasound imaging quantified the reduction in pre-focal bubble nuclei lifetime.
- Stone fragmentation was assessed by measuring the percentage of mass less than 2 mm after shock exposure.
Main Results:
- The degassed water jet reduced bubble nuclei lifetime from 7 to 0.3 seconds.
- Stone fragmentation improved from 22 ± 6% to 33 ± 5% (p=0.007) after 250 shocks at 1 Hz.
- Stone fragmentation increased from 18 ± 6% to 28 ± 8% (p=0.04) after 500 shocks at 2 Hz with an 8 cm tissue phantom.
Conclusions:
- Cavitation bubbles critically influence stone comminution in lithotripsy.
- Removing cavitation nuclei via a water jet is a viable strategy to improve lithotripter efficacy.
- This method offers a potential enhancement for contemporary shock wave lithotripsy treatments.
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