The physics and mechanics of lithotripters

Lubock, Paul

doi:10.1007/bf01536363

Cited by 20 publications

(6 citation statements)

References 6 publications

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“…Currently, the established mechanisms of stone failure in SWL are dynamic fatigue (Lokhandwalla and Sturtevant 2000), spallation (Chuong et al 1989; Lubock 1989; Vakil et al 1991; Dahake and Gracewski 1997; Xi and Zhong 2001), geometric superfocusing (Gracewski et al 1993; Xi and Zhong 2001), squeezing (Eisenmenger 2001), shear-induced failure (Xi and Zhong 2001; Cleveland and Sapozhnikov 2005; Sapozhnikov et al 2007), and cavitation (Coleman et al 1987; Crum 1988; Sass et al 1991; Philipp and Lauterborn 1998; Zhu et al 2002). The challenge of SWL research in recent years has been to correlate LSW parameters to fracture mechanisms in order to better guide lithotripter design and usage.…”

Section: Discussionmentioning

confidence: 99%

Stone comminution correlates with the average peak pressure incident on a stone during shock wave lithotripsy

Smith¹,

Zhong²

2012

Journal of Biomechanics

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To investigate the roles of lithotripter shock wave (LSW) parameters and cavitation in stone comminution, a series of in vitro fragmentation experiments have been conducted in water and 1,3-butanediol (a cavitation-suppressive fluid) at a variety of acoustic field positions of an electromagnetic shock wave lithotripter. Using field mapping data and integrated parameters averaged over a circular stone holder area (Rh = 7 mm), close logarithmic correlations between the average peak pressure (P+(avg)) incident on the stone (D = 10 mm BegoStone) and comminution efficiency after 500 and 1,000 shocks have been identified. Moreover, the correlations have demonstrated distinctive thresholds in P+(avg) (5.3 MPa and 7.6 MPa for soft and hard stones, respectively), that are required to initiate stone fragmentation independent of surrounding fluid medium and LSW dose. These observations, should they be confirmed using other shock wave lithotripters, may provide an important field parameter (i.e., P+(avg)) to guide appropriate application of SWL in clinics, and facilitate device comparison and design improvements in future lithotripters.

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Section: Discussionmentioning

confidence: 99%

Stone comminution correlates with the average peak pressure incident on a stone during shock wave lithotripsy

Smith¹,

Zhong²

2012

Journal of Biomechanics

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“…Multiple mechanisms of stone fragmentation have been proposed, including spalling (Chaussy et al 1980; Whelan and Finlayson 1988; Lubock 1989), cavitation (Coleman et al 1987; Crum 1988; Holmer et al 1991), compression-induced tensile failure (Chaussy et al 1980; Chaussy 1982; Lokhandwalla and Sturtevant 2000), quasi-static squeezing (Eisenmenger 2001) and dynamic squeezing with emphasis on shear wave generation (Sapozhnikov et al 2007). Among them, spalling (Xi and Zhong 2001; Mihradi et al 2004), cavitation (Zohdi and Szeri 2005) and shear wave stress (Cleveland and Sapozhnikov 2005) have been shown to depend critically on the size or geometry of the stone.…”

Section: Introductionmentioning

confidence: 99%

Effects of Stone Size on the Comminution Process and Efficiency in Shock Wave Lithotripsy

Zhang

Nault

Mitran

et al. 2016

Ultrasound in Medicine & Biology

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The effects of stone size on the process and comminution efficiency in shock wave lithotripsy (SWL) are investigated by experiments, numerical simulations, and scale analysis. Cylindrical BegoStone phantoms with approximately equal height and diameter of either 4-, or 7- or 10-mm, in a total aggregated mass of about 1.5 g, were treated in an electromagnetic shock wave lithotripter field. The resultant stone comminution (SC) was found to correlate closely with the average peak pressure, P+(avg), incident on the stones. The P+(avg) threshold to initiate stone fragmentation in water increased from 7.9 to 8.8 to 12.7 MPa, respectively, when the stone size decreased from 10 to 7 to 4 mm. Similar changes in the P+(avg) threshold were observed for the 7- and 10-mm stones treated in 1,3-butanediol where cavitation is suppressed, suggesting that the observed size dependency is due to changes in stress distribution within different size stones. Moreover, the slope of the correlation curve between SC and ln(Pfalse‒+(avg)) in water increased with decreasing stone size, while the opposite trend was observed in 1,3-butanediol. The progression of stone comminution in SWL showed a size-dependency with the 7- and 10-mm stones fragmented into progressively smaller pieces while a significant portion (> 30%) of the 4-mm stones were stalemated within the size range of 2.8 ~ 4 mm even after 1,000 shocks. Analytical scaling considerations suggest size-dependent fragmentation behaviour, a hypothesis further supported by numerical model calculations that exhibit changing patterns of constructive and destructive wave interference, and thus variations in the maximum tensile stress or stress integral produced in cylindrical and spherical stone of different sizes.

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“…Specifically, numerous studies have been conducted to dissect the role of stress waves and cavitation in stone fracture (Zhu et al, 2002;Sapozhnikov et al, 2007). Many proposed mechanisms, such as spallation (Lubock, 1989), geometric superfocusing (Gracewski et al, 1993;Xi and Zhong, 2001), circumferential squeezing (Eisenmenger, 2001), and shear-induced failure (Xi and Zhong, 2001;Cleveland and Sapozhnikov, 2005;Sapozhnikov et al, 2007) were demonstrated during the fragmentation process in the early stage of SWL, when the stones are of sufficient size to favor the development of large stress concentrations. Other proposed mechanisms, such as dynamic fatigue (Lokhandwalla and Sturtevant, 2000) and cavitation (Coleman et al, 1987;Sass et al, 1991;Philipp and Lauterborn, 1998), describe processes that influence stone fragmentation throughout the entire course of SWL.…”

Section: Introductionmentioning

confidence: 99%

A heuristic model of stone comminution in shock wave lithotripsy

Smith

Zhong

2013

The Journal of the Acoustical Society of America

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A heuristic model is presented to describe the overall progression of stone comminution in shock wave lithotripsy (SWL), accounting for the effects of shock wave dose and the average peak pressure, P þ(avg) , incident on the stone during the treatment. The model is developed through adaptation of the Weibull theory for brittle fracture, incorporating threshold values in dose and P þ(avg) that are required to initiate fragmentation. The model is validated against experimental data of stone comminution from two stone types (hard and soft BegoStone) obtained at various positions in lithotripter fields produced by two shock wave sources of different beam width and pulse profile both in water and in 1,3-butanediol (which suppresses cavitation). Subsequently, the model is used to assess the performance of a newly developed acoustic lens for electromagnetic lithotripters in comparison with its original counterpart both under static and simulated respiratory motion. The results have demonstrated the predictive value of this heuristic model in elucidating the physical basis for improved performance of the new lens. The model also provides a rationale for the selection of SWL treatment protocols to achieve effective stone comminution without elevating the risk of tissue injury.

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The physics and mechanics of lithotripters

Cited by 20 publications

References 6 publications

Stone comminution correlates with the average peak pressure incident on a stone during shock wave lithotripsy

Stone comminution correlates with the average peak pressure incident on a stone during shock wave lithotripsy

Effects of Stone Size on the Comminution Process and Efficiency in Shock Wave Lithotripsy

A heuristic model of stone comminution in shock wave lithotripsy

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