Bubble Proliferation in Shock Wave Lithotripsy Occurs during Inertial Collapse

Pishchalnikov, Yuri A.; McAteer, James A.; Pishchalnikova, Irina V.; Williams, James C.; Bailey, Michael R.; Sapozhnikov, Oleg A.; Enflo, B. O.; Hedberg, Claes; Kari, Leif

doi:10.1063/1.2956259

Cited by 14 publications

(21 citation statements)

References 3 publications

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“…The residual pressure oscillations are understood to be due to fading oscillations of electric current during the discharge of the high-voltage capacitor through the coil of the SW generator. 6 …”

Section: Methodsmentioning

confidence: 99%

“…2,3 Even though the growth-collapse cycle of cavitation bubbles is short compared to the interval between SWs, more bubbles are generated at fast PRFs resulting in a reduction in delivery of SW energy to the stone. 1,2,[4][5][6] We sought to characterize the growth of bubble clouds produced by lithotripter SWs and looked for evidence that bubble proliferation at fast PRF is due to SWs interacting with cavitation nuclei generated by previous SWs.…”

Section: Introductionmentioning

confidence: 99%

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Bubble proliferation in the cavitation field of a shock wave lithotripter

Pishchalnikov

Williams

McAteer

2011

The Journal of the Acoustical Society of America

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Lithotripter shock waves (SWs) generated in non-degassed water at 0.5 and 2 Hz pulse repetition frequency (PRF) were characterized using a fiber-optic hydrophone. High-speed imaging captured the inertial growth-collapse-rebound cycle of cavitation bubbles, and continuous recording with a 60 fps camcorder was used to track bubble proliferation over successive SWs. Microbubbles that seeded the generation of bubble clouds formed by the breakup of cavitation jets and by bubble collapse following rebound. Microbubbles that persisted long enough served as cavitation nuclei for subsequent SWs, as such bubble clouds were enhanced at fast PRF. Visual tracking suggests that bubble clouds can originate from single bubbles.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Bubble proliferation in the cavitation field of a shock wave lithotripter

Pishchalnikov

Williams

McAteer

2011

The Journal of the Acoustical Society of America

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“…21,22 It was found that inertial collapse and jetting of primary SW-induced bubbles produces a cloud of smaller daughter nuclei, with a single primary bubble giving rise to dozens of residual daughters. Furthermore, as bubbles proliferated from shot to shot, the amplitude of the negative phase of the SWs was observed to decline.…”

Section: Duryea Et Almentioning

confidence: 99%

“…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. 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.…”

Section: Introductionmentioning

confidence: 99%

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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“…However, the residual micron-sized bubbles following a cavitation cloud collapse have a longer lifespan on the order of 1 second and thus a large fraction would be expected to persist between subsequent SWs, particularly at higher firing rates. 2,[16][17][18] On subsequent pulses, these nuclei absorb energy from the negative pressure phase of the lithotripter waveform, reducing cavitation on the surface of the stone, which in turn reduces the efficacy of stone comminution. 2 In our previous studies, low-amplitude acoustic bursts were used with in vitro models to actively remove residual cavitation bubbles through forced coalescence.…”

Section: Introductionmentioning

confidence: 99%

Enhanced High-Rate Shockwave Lithotripsy Stone Comminution in an In Vivo Porcine Model Using Acoustic Bubble Coalescence

Tamaddoni

Roberts

Duryea³

et al. 2016

Journal of Endourology

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Cavitation plays a significant role in the efficacy of stone comminution during shockwave lithotripsy (SWL). Although cavitation on the surface of urinary stones helps to improve fragmentation, cavitation bubbles along the propagation path may shield or block subsequent shockwaves (SWs) and potentially induce collateral tissue damage. Previous in vitro work has shown that applying low-amplitude acoustic waves after each SW can force bubbles to consolidate and enhance SWL efficacy. In this study, the feasibility of applying acoustic bubble coalescence (ABC) in vivo was tested. Model stones were percutaneously implanted and treated with 2500 lithotripsy SWs at 120 SW/minute with or without ABC. Comparing the results of stone comminution, a significant improvement was observed in the stone fragmentation process when ABC was used. Without ABC, only 25% of the mass of the stone was fragmented to particles <2 mm in size. With ABC, 75% of the mass was fragmented to particles <2 mm in size. These results suggest that ABC can reduce the shielding effect of residual bubble nuclei, resulting in a more efficient SWL treatment.

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Bubble Proliferation in Shock Wave Lithotripsy Occurs during Inertial Collapse

Cited by 14 publications

References 3 publications

Bubble proliferation in the cavitation field of a shock wave lithotripter

Bubble proliferation in the cavitation field of a shock wave lithotripter

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

Enhanced High-Rate Shockwave Lithotripsy Stone Comminution in an In Vivo Porcine Model Using Acoustic Bubble Coalescence

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