Cavitation selectively reduces the negative-pressure phase of lithotripter shock pulses

Pishchalnikov, Yuri A.; Sapozhnikov, Oleg A.; Bailey, Michael R.; Pishchalnikova, Irina V.; Williams, James C.; McAteer, James A.

doi:10.1121/1.2127115

Cited by 64 publications

(76 citation statements)

References 9 publications

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“…22 When an SW propagates through a medium containing residual cavitation nuclei, the negative phase of the waveform is attenuated as it causes these preexisting nuclei to swell. 1,16,23,24 That is, energy is extracted from the tensile…”

Section: Discussionmentioning

confidence: 99%

“…16 In this way, the energy that ultimately propagates to the stone is reduced, and the efficacy of comminution is hindered. A more pronounced effect is observed at high rates due to the fact that residual cavitation nuclei have less time to passively dissolve between successive SWs.…”

Section: Duryea Et Almentioning

confidence: 99%

“…However, the tensile component of the SW will cause bubble nuclei to grow-a process that removes energy from the negative tail of the SW and transfers it to the propagation medium in the form of kinetic and potential energy of the fluid surrounding the bubbles. 16 As such, the negative phase of the SW that ultimately reaches the stone is attenuated in both time and amplitude, leading to decreased efficacy of stone comminution. This effect is more pronounced at high shock rates, as residual cavitation nuclei have less time to passively dissolve between successive SWs.…”

Section: Introductionmentioning

confidence: 99%

“…21,22 A SW that propagates through a medium containing residual cavitation nuclei will experience selective attenuation of its negative phase. 1,16,23,24 Since the cavitation nuclei are very small (<10 lm), 24 they do not affect the compressional portion of the waveform. However, the tensile component of the SW will cause bubble nuclei to grow-a process that removes energy from the negative tail of the SW and transfers it to the propagation medium in the form of kinetic and potential energy of the fluid surrounding the bubbles.…”

Section: Introductionmentioning

confidence: 99%

“…It is well documented that SWs can generate extensive cavitation activity along their propagation path, with the size and density of the bubble population increasing with an increase in shock rate. 1,[14][15][16] The lifespan of SW-induced bubbles has been reported to be on the order of 1 ms, [17][18][19][20] implying that they will undergo inertial collapse well before the arrival of the subsequent SW. However, recent work has shown that collapse of these primary bubbles produces a large population of smaller daughter bubbles-that is, cavitation nuclei-which can persist on the order of 1 second.…”

Section: Introductionmentioning

confidence: 99%

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Acoustic Bubble Removal to Enhance SWL Efficacy at High Shock Rate: An In Vitro Study

Duryea

Roberts

Cain

et al. 2014

Journal of Endourology

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Rate-dependent efficacy has been extensively documented in shock wave lithotripsy (SWL) stone comminution, with shock waves (SWs) delivered at a low rate producing more efficient fragmentation in comparison to those delivered at high rates. Cavitation is postulated to be the primary source underlying this rate phenomenon. Residual bubble nuclei that persist along the axis of SW propagation can drastically attenuate the waveform's negative phase, decreasing the energy which is ultimately delivered to the stone and compromising comminution. The effect is more pronounced at high rates, as residual nuclei have less time to passively dissolve between successive shocks. In this study, we investigate a means of actively removing such nuclei from the field using a low-amplitude acoustic pulse designed to stimulate their aggregation and subsequent coalescence. To test the efficacy of this bubble removal scheme, model kidney stones were treated in vitro using a research electrohydraulic lithotripter. SWL was applied at rates of 120, 60, or 30 SW/min with or without the incorporation of bubble removal pulses. Optical images displaying the extent of cavitation in the vicinity of the stone were also collected for each treatment. Results show that bubble removal pulses drastically enhance the efficacy of stone comminution at the higher rates tested (120 and 60 SW/min), while optical images show a corresponding reduction in bubble excitation along the SW axis when bubble removal pulses are incorporated. At the lower rate of 30 SW/min, no difference in stone comminution or bubble excitation was detected with the addition of bubble removal pulses, suggesting that remnant nuclei had sufficient time for more complete dissolution. These results corroborate previous work regarding the role of cavitation in rate-dependent SWL efficacy, and suggest that the effect can be mitigated via appropriate control of the cavitation environment surrounding the stone.

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