Removal of residual nuclei following a cavitation event using low-amplitude ultrasound

Duryea, Alexander P.; Cain, Charles A.; Tamaddoni, Hedieh Alavi; Roberts, William W.; Hall, Timothy L.

doi:10.1109/tuffc.2014.006316

Cited by 24 publications

(46 citation statements)

References 47 publications

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“…This secondary Bjerknes force is hypothesized to be the dominant mechanism bringing the remnant bubbles from SWL cavitation together to coalesce and clear the propagation path. 1,20 In general, the degree of coalescence required for effective clearance of the propagation path to mitigate effects of bubble shielding is not known. This suggests the potential for further optimization of acoustic parameters for ABC for further improvement in fragmentation efficiency.…”

Section: Discussionmentioning

confidence: 99%

“…2 In our previous studies, low-amplitude acoustic bursts were used with in vitro models to actively remove residual cavitation bubbles through forced coalescence. 1,19,20 Significant improvement was demonstrated in the comminution efficacy of SWL at higher rates (120 and 60 SW/minute). In this study, the feasibility of SWL stone comminution at 120 SW/minute with acoustic bubble coalescence (ABC) was evaluated on a porcine model and compared to standard SWL at the same rate.…”

Section: Introductionmentioning

confidence: 96%

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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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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

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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“…The experimental setup used to investigate the effects of bubble removal pulse frequency was the same as that described previously [23], with the addition of a needle hydrophone (Müller-Platte Needle Probe 100-100-1, Dr. Müller Instruments, Oberursel, Germany) positioned adjacent to the histotripsy transducer focus at an offset distance of 2 mm, distal relative to the bubble removal module (Fig. 1).…”

Section: Methodsmentioning

confidence: 99%

“…In our previous work we have explored a strategy for the active removal of these remnant nuclei following a cavitation event [23], with the ultimate goal of mitigating the ill-effects of residual bubbles in cavitation-based ultrasound therapies. It was shown that the application of appropriately designed low amplitude ultrasound pulses can stimulate the aggregation and subsequent coalescence of residual bubble nuclei, in effect removing them from the field.…”

Section: Introductionmentioning

confidence: 99%

“…When brought into close proximity with one another, bubbles that are of similar size experience an attractive force, further promoting their consolidation (secondary Bjerknes force) [24, 25, 28, 29]. Our previous results indicate that the secondary Bjerknes force is likely the dominant facilitator of the bubble consolidation process, with a select set of acoustic parameters producing optimal aggregation and coalescence [23]. …”

Section: Introductionmentioning

confidence: 99%

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Removal of residual nuclei following a cavitation event: a parametric study

Duryea

Tamaddoni

Cain

et al. 2015

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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The efficacy of ultrasound therapies such as shock wave lithotripsy and histotripsy can be compromised by residual cavitation bubble nuclei that persist following the collapse of primary cavitation. In our previous work, we have developed a unique strategy for mitigating the effects of these residual bubbles using low amplitude ultrasound pulses to stimulate their aggregation and subsequent coalescence—effectively removing them from the field. Here, we further develop this bubble removal strategy through an investigation of the effect of frequency on the consolidation process. Bubble removal pulses ranging from 0.5 – 2 MHz were used to sonicate the population of residual nuclei produced upon collapse of a histotripsy bubble cloud. For each frequency, mechanical index (MI) values ranging from 0 to approximately 1.5 were tested. Results indicated that, when evaluated as a function of bubble removal pulse MI, the efficacy of bubble removal shows markedly similar trends for all frequencies tested. This behavior divides into three distinct regimes (with provided cutoffs being approximate): (1) MI < 0.2: Minimal effect on the population of remnant cavitation nuclei; (2) 0.2 < MI < 1: Aggregation and subsequent coalescence of residual bubbles, the extent of which trends toward a maximum; (3) MI > 1: Bubble coalescence is compromised as bubble removal pulses induce high magnitude inertial cavitation of residual bubbles. The major distinction in these trends came for bubble removal pulses applied at 2 MHz, which were observed to generate the most effective bubble coalescence of all frequencies tested. We hypothesize that this is a consequence of the secondary Bjerknes force being the major facilitator of the consolidation process, the magnitude of which increases when the bubble size distribution is far from resonance such that the phase difference of oscillation of individual bubbles is minimal.

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Novel acoustic coupling bath using magnetite nanoparticles for MR‐guided transcranial focused ultrasound surgery

et al. 2019

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Purpose Acoustic coupling baths, nominally composed of degassed water, play important roles during transcranial focused ultrasound surgery. However, this large water bolus also degrades the quality of intraoperative magnetic resonance (MR) guidance imaging. In this study, we test the feasibility of using dilute, aqueous magnetite nanoparticle suspensions to suppress these image degradations while preserving acoustic compatibility. We examine the effects of these suspensions on metrics of image quality and acoustic compatibility for two types of transcranial focused ultrasound insonation regimes: low‐duty cycle histotripsy procedures and high‐duty cycle thermal ablation procedures. Methods Magnetic resonance guidance imaging was used to monitor thermal ablations of in vitro gel targets using a coupling bath composed of various concentrations of aqueous, suspended, magnetite nanoparticles in a clinical transcranial transducer under stationary and flowing conditions. Thermal deposition was monitored using MR thermometry simultaneous to insonation. Then, using normal degassed water as a coupling bath, various concentrations of aqueous, suspended, magnetite nanoparticles were placed at the center of this same transducer and insonated using high‐duty cycle pulsing parameters. Passive cavitation detectors recorded cavitation emissions, which were then used to estimate the relative number of cavitation events per insonation (cavitation duty cycle) and the cavitation dose estimates of each nanoparticle concentration. Finally, the nanoparticle mixtures were exposed to low‐duty cycle, histotripsy pulses. Passive cavitation detectors monitored cavitation emissions, which were used to estimate cavitation threshold pressures. Results The nanoparticles reduced the MR signal of the coupling bath by 90% in T2‐ and T2*‐weighted images and also removed almost all imaging artifacts caused by coupling bath motion. The coupling baths caused <5% changes in peak temperature change achieved during sonication, as observed via MR thermometry. At low duty cycle insonations, the nanoparticles decreased the cavitation threshold pressure by about 15 ± 7% in a manner uncorrelated with nanoparticle concentration. At high duty cycle insonations, the 0.5 cavitation duty cycle acoustic power threshold varied linearly with nanoparticle concentration. Conclusions Dilute aqueous magnetite nanoparticle suspensions effectively reduced MR imaging artifacts caused by the acoustic coupling bath. They also attenuated acoustic power deposition by <5%. For low duty cycle insonation regimes, the nanoparticles decreased the cavitation threshold by 15 ± 7%. However, for high‐duty cycle regimes, the nanoparticles decreased the threshold for cavitation in proportion to nanoparticle concentration.

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Removal of residual nuclei following a cavitation event using low-amplitude ultrasound

Cited by 24 publications

References 47 publications

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

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

Removal of residual nuclei following a cavitation event: a parametric study

Novel acoustic coupling bath using magnetite nanoparticles for MR‐guided transcranial focused ultrasound surgery

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