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Pei Zhong - One of the best experts on this subject based on the ideXlab platform.
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assessing the effect of Lithotripter focal width on the fracture potential of stones in shockwave lithotripsy
Journal of the Acoustical Society of America, 2017Co-Authors: Shunxiang Cao, Pei Zhong, Ying Zhang, Defei Liao, Kevin G WangAbstract:This talk presents a combination of computational and experimental study on the effect of Lithotripter focal width on the fracture potential of stones treated at various distances from the Lithotripter focus. Two representative Lithotripter fields are considered: (1) the original Siemens Modularis with a focal width of 7.4 mm and (2) a modified version with a larger focal width of 11.0 mm with comparable acoustic pulse energy of 40 mJ. The interaction of these two Lithotripter fields with spherical and cylindrical model stones located at 0 to 12 mm from the shock wave axis is investigated. Specifically, a three-dimensional CFD (Computational Fluid Dynamics)—CSD (Computational Solid Dynamics) coupled computational framework is used to simulate the propagation of stress waves, as well as the initiation and propagation of fractures. The two-scale Tuler-Butcher fracture criterion will be employed: it will be calibrated experimentally, then applied to assessing stress-induced stone damage. An element deletion ...
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pd18 11 comparison of an electric pulse Lithotripter to the holmium laser stone fragmentation efficiency and impact on flexible ureteroscope deflection and flow
The Journal of Urology, 2016Co-Authors: Adam Kaplan, Georgy Sankin, Pei Zhong, Joanne Dale, Daniela Radvak, Richard Shin, Anika Ackerman, Tony Chen, Fernando Cabrera, Charles D. ScalesAbstract:INTRODUCTION AND OBJECTIVES: A new intracorporeal lithotriptor uses a nanosecond duration electrical discharge through a flexible coaxial probe to endoscopically fragment urinary stones. This device was compared to a holmium laser with regards to stone fragmentation efficiency and their impact on flexible ureteroscope deflection and flow of irrigation. METHODS: Using a custom bench model, stone fragmentation efficiency of the Nano-electric Pulse Lithotriptor (NPL, Lithotech Group, Israel) was evaluated with a begostone (mixture 5:2) confined under 0.9% normal saline atop sequential mesh sieves. Two NPL probe sizes (2.0 and 3.6F) and two holmium laser fibers (200 mm and 365mm) were evaluated using 6mm begostones. Time to first break, time to complete break (all fragments <3mm), and overall fragment sizes were measured. Ureteroscope deflection was tested in 5 new 4th generation flexible ureteroscopes, with an empty channel followed by placement of a 2.0F NPL probe, a 2.4F NPL probe, a 200mm laser fiber, and a 1.9F wire basket. Ureteroscope irrigation flow was measured using normal saline at 100 cm, with an empty channel and then with a 2.0F NEP probe, a 200mm laser fiber, and a 1.9F wire basket. RESULTS: The 2.0F NPL showed improved stone fragmentation efficiency compared to the 200mm laser (86 mg/min vs. 52 mg/min, p 1⁄4 0.014) as did the 3.6F NPL vs. the 365mm laser (173 mg/min vs. 80 mg/min, p1⁄40.05). The NPL created more 1-2 mm fragments, while the laser created more dust (< 1 mm fragments); the difference was more pronounced between the larger NPL and laser probes. In the 5 ureteroscopes tested, ureteroscope deflection was reduced by an average of 3.75 with the 2.0F NPL probe and 22.25 with the 2.4F NLP probe (compared to 5.25 with the laser and 2.75 with the basket). Irrigation flow through the ureteroscope was 36.5 ml/min on average, and was reduced to 18.3 ml/min with the 200mm laser fiber, and to 6.3 ml/min with the 2.0F NEP probe. CONCLUSIONS: The Nano-electric pulse Lithotripter produces improved stone fragmentation efficiency as compared to the holmium laser. However the 2.0F and 2.4F NPL probes limit flow and the 2.4F probe limits ureteroscope deflection.
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stone comminution correlates with the average peak pressure incident on a stone during shock wave lithotripsy
Journal of Biomechanics, 2012Co-Authors: Nathan Smith, Pei ZhongAbstract:Abstract 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 ( R h =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 1000 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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a comparison of light spot hydrophone and fiber optic probe hydrophone for Lithotripter field characterization
Review of Scientific Instruments, 2012Co-Authors: Nathan Smith, Ralf Nanke, Jens Fehre, Walter Neal Simmons, Georgy Sankin, Pei ZhongAbstract:The performance of a newly developed light spot hydrophone (LSHD) in Lithotripter field characterization was compared to that of the fiber optic probe hydrophone (FOPH). Pressure waveforms produced by a stable electromagnetic shock wave source were measured by the LSHD and FOPH under identical experimental conditions. In the low energy regime, focus and field acoustic parameters matched well between the two hydrophones. At clinically relevant high energy settings for shock wave lithotripsy, the measured leading compressive pressure waveforms matched closely with each other. However, the LSHD recorded slightly larger |P–| (p < 0.05) and secondary peak compressive pressures (p < 0.01) than the FOPH, leading to about 20% increase in total acoustic pulse energy calculated in a 6 mm radius around the focus (p = 0.06). Tensile pulse durations deviated ∼5% (p < 0.01) due to tensile wave shortening from cavitation activity using the LSHD. Intermittent compression spikes and laser light reflection artifacts have been correlated to bubble activity based on simultaneous high-speed imaging analysis. Altogether, both hydrophones are adequate for Lithotripter field characterization as specified by the international standard IEC 61846.
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effect of Lithotripter focal width on stone comminution in shock wave lithotripsy
Journal of the Acoustical Society of America, 2010Co-Authors: Neal W Simmons, Georgy Sankin, Pei ZhongAbstract:Using a reflector insert, the original HM-3 Lithotripter field at 20 kV was altered significantly with the peak positive pressure (p+) in the focal plane increased from 49 to 87 MPa while the −6 dB focal width decreased concomitantly from 11 to 4 mm. Using the original reflector, p+ of 33 MPa with a −6 dB focal width of 18 mm were measured in a pre-focal plane 15-mm proximal to the Lithotripter focus. However, the acoustic pulse energy delivered to a 28-mm diameter area around the Lithotripter axis was comparable (∼120 mJ). For all three exposure conditions, similar stone comminution (∼70%) was produced in a mesh holder of 15 mm after 250 shocks. In contrast, stone comminution produced by the modified reflector either in a 15-mm finger cot (45%) or in a 30-mm membrane holder (14%) was significantly reduced from the corresponding values (56% and 26%) produced by the original reflector (no statistically significant differences were observed between the focal and pre-focal planes). These observations suggest...
Olivier Traxer - One of the best experts on this subject based on the ideXlab platform.
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update on lasers in urology 2014 current assessment on holmium yttrium aluminum garnet ho yag laser Lithotripter settings and laser fibers
World Journal of Urology, 2015Co-Authors: Peter Kronenberg, Olivier TraxerAbstract:The purpose of the study was to review the existing literature on holmium:yttrium–aluminum–garnet laser lithotripsy regarding Lithotripter settings and laser fibers. An online search of current and past peer-reviewed literature on holmium laser lithotripsy was performed on several databases, including PubMed, SciElo, and Google Scholar. Relevant studies and original articles about Lithotripter settings and laser fibers were examined, and the most important information is summarized and presented here. We examine how the choice of Lithotripter settings and laser fibers influences the performance of holmium laser lithotripsy. Traditional laser Lithotripter settings are analyzed, including pulse energy, pulse frequency, and power levels, as well as newly developed long-pulse modes. The impact of these settings on ablation volume, fragment size, and retropulsion is also examined. Advantages of small- and large-diameter laser fibers are discussed, and controversies are highlighted. Additionally, the influence of the laser fiber is examined, specifically the fiber tip preparation and the Lithotripter settings’ influence on tip degradation. Many technical factors influence the performance of holmium laser lithotripsy. Knowing and understanding these controllable parameters allows the urologist to perform a laser lithotripsy procedure safely, efficiently, and with few complications.
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update on lasers in urology 2014 current assessment on holmium yttrium aluminum garnet ho yag laser Lithotripter settings and laser fibers
World Journal of Urology, 2015Co-Authors: Peter Kronenberg, Olivier TraxerAbstract:Purpose The purpose of the study was to review the existing literature on holmium:yttrium–aluminum–garnet laser lithotripsy regarding Lithotripter settings and laser fibers.
Peter Kronenberg - One of the best experts on this subject based on the ideXlab platform.
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update on lasers in urology 2014 current assessment on holmium yttrium aluminum garnet ho yag laser Lithotripter settings and laser fibers
World Journal of Urology, 2015Co-Authors: Peter Kronenberg, Olivier TraxerAbstract:The purpose of the study was to review the existing literature on holmium:yttrium–aluminum–garnet laser lithotripsy regarding Lithotripter settings and laser fibers. An online search of current and past peer-reviewed literature on holmium laser lithotripsy was performed on several databases, including PubMed, SciElo, and Google Scholar. Relevant studies and original articles about Lithotripter settings and laser fibers were examined, and the most important information is summarized and presented here. We examine how the choice of Lithotripter settings and laser fibers influences the performance of holmium laser lithotripsy. Traditional laser Lithotripter settings are analyzed, including pulse energy, pulse frequency, and power levels, as well as newly developed long-pulse modes. The impact of these settings on ablation volume, fragment size, and retropulsion is also examined. Advantages of small- and large-diameter laser fibers are discussed, and controversies are highlighted. Additionally, the influence of the laser fiber is examined, specifically the fiber tip preparation and the Lithotripter settings’ influence on tip degradation. Many technical factors influence the performance of holmium laser lithotripsy. Knowing and understanding these controllable parameters allows the urologist to perform a laser lithotripsy procedure safely, efficiently, and with few complications.
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update on lasers in urology 2014 current assessment on holmium yttrium aluminum garnet ho yag laser Lithotripter settings and laser fibers
World Journal of Urology, 2015Co-Authors: Peter Kronenberg, Olivier TraxerAbstract:Purpose The purpose of the study was to review the existing literature on holmium:yttrium–aluminum–garnet laser lithotripsy regarding Lithotripter settings and laser fibers.
Andrew J Szeri - One of the best experts on this subject based on the ideXlab platform.
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dynamics of bubbles near a rigid surface subjected to a Lithotripter shock wave part 2 reflected shock intensifies non spherical cavitation collapse
Journal of Fluid Mechanics, 2008Co-Authors: Michael L Calvisi, Jonathan Iloreta, Andrew J SzeriAbstract:In this paper we use the boundary integral method to model the non-spherical collapse of bubbles excited by Lithotripter shock waves near a rigid boundary. The waves we consider are representative of those developed by shock wave lithotripsy or shock wave therapy devices, and the rigid boundaries we consider are representative of kidney stones and reflective bony tissue. This study differs from previous studies in that we account for the reflection of the incident wave and also the asymmetry of the collapse caused by the presence of the rigid surface. The presence of the boundary causes interference between reflected and incident waves. Quantities such as kinetic energy, Kelvin impulse and centroid translation are calculated in order to illuminate the physics of the collapse process. The main finding is that the dynamics of the bubble collapse depend strongly on the distance of the bubble relative to the wall when reflection is taken into account, but much less so when reflection is omitted from the model. The reflection enhances the expansion and subsequent collapse of bubbles located near the boundary owing to constructive interference between incident and reflected waves; however, further from the boundary, the dynamics of collapse are suppressed owing to destructive interference of these two waves. This result holds regardless of the initial radius of the bubble or its initial state at the time of impact with the Lithotripter shock wave. Also, the work done by the Lithotripter shock wave on the bubble is shown to predict strongly the maximum bubble volume regardless of the standoff distance and the presence or absence of reflection; furthermore, allowing for non-sphericity, these predictions match almost exactly those of a previously developed spherical model.
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dynamics of bubbles near a rigid surface subjected to a Lithotripter shock wave part 1 consequences of interference between incident and reflected waves
Journal of Fluid Mechanics, 2008Co-Authors: Jonathan Iloreta, N M Fung, Andrew J SzeriAbstract:In this paper we consider the dynamics of bubbles near a kidney stone subjected to a Lithotripter shock wave. We address the effect of kidney stone geometry and composition on the cavitation potential near the stone in a shock wave Lithotripter. The analysis is based on the previously developed work metric in which the work done on a bubble by the Lithotripter shock wave (LSW) is used to determine the maximum radius the bubble achieves. Results of the reflection of the LSW from cylindrical kidney stones with proximal surfaces of varying geometry show that the presence of the stone enhances bubble growth near the stone and decreases growth further away, owing to constructive and destructive interference, respectively. These effects hold true regardless of the shape and curvature of the face, and are strongest for stones with concave faces and higher reflection coefficients. A consequence of the analysis is an elucidation of the mechanism for enhanced cavitation activity and creation of deep craters on the proximal side of a kidney stone, as have been observed in recent experiments.
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Interaction of Lithotripter shockwaves with single inertial cavitation bubbles
Journal of Fluid Mechanics, 2007Co-Authors: Evert Klaseboer, Georgy Sankin, Michael L Calvisi, Andrew J Szeri, Siew Wan Fong, Cary K. Turangan, Boo Cheong Khoo, Pei ZhongAbstract:: The dynamic interaction of a shockwave (modelled as a pressure pulse) with an initially spherically oscillating bubble is investigated. Upon the shockwave impact, the bubble deforms non-spherically and the flow field surrounding the bubble is determined with potential flow theory using the boundary-element method (BEM). The primary advantage of this method is its computational efficiency. The simulation process is repeated until the two opposite sides of the bubble surface collide with each other (i.e. the formation of a jet along the shockwave propagation direction). The collapse time of the bubble, its shape and the velocity of the jet are calculated. Moreover, the impact pressure is estimated based on water-hammer pressure theory. The Kelvin impulse, kinetic energy and bubble displacement (all at the moment of jet impact) are also determined. Overall, the simulated results compare favourably with experimental observations of Lithotripter shockwave interaction with single bubbles (using laser-induced bubbles at various oscillation stages). The simulations confirm the experimental observation that the most intense collapse, with the highest jet velocity and impact pressure, occurs for bubbles with intermediate size during the contraction phase when the collapse time of the bubble is approximately equal to the compressive pulse duration of the shock wave. Under this condition, the maximum amount of energy of the incident shockwave is transferred to the collapsing bubble. Further, the effect of the bubble contents (ideal gas with different initial pressures) and the initial conditions of the bubble (initially oscillating vs. non-oscillating) on the dynamics of the shockwave-bubble interaction are discussed.
Georgy Sankin - One of the best experts on this subject based on the ideXlab platform.
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pd18 11 comparison of an electric pulse Lithotripter to the holmium laser stone fragmentation efficiency and impact on flexible ureteroscope deflection and flow
The Journal of Urology, 2016Co-Authors: Adam Kaplan, Georgy Sankin, Pei Zhong, Joanne Dale, Daniela Radvak, Richard Shin, Anika Ackerman, Tony Chen, Fernando Cabrera, Charles D. ScalesAbstract:INTRODUCTION AND OBJECTIVES: A new intracorporeal lithotriptor uses a nanosecond duration electrical discharge through a flexible coaxial probe to endoscopically fragment urinary stones. This device was compared to a holmium laser with regards to stone fragmentation efficiency and their impact on flexible ureteroscope deflection and flow of irrigation. METHODS: Using a custom bench model, stone fragmentation efficiency of the Nano-electric Pulse Lithotriptor (NPL, Lithotech Group, Israel) was evaluated with a begostone (mixture 5:2) confined under 0.9% normal saline atop sequential mesh sieves. Two NPL probe sizes (2.0 and 3.6F) and two holmium laser fibers (200 mm and 365mm) were evaluated using 6mm begostones. Time to first break, time to complete break (all fragments <3mm), and overall fragment sizes were measured. Ureteroscope deflection was tested in 5 new 4th generation flexible ureteroscopes, with an empty channel followed by placement of a 2.0F NPL probe, a 2.4F NPL probe, a 200mm laser fiber, and a 1.9F wire basket. Ureteroscope irrigation flow was measured using normal saline at 100 cm, with an empty channel and then with a 2.0F NEP probe, a 200mm laser fiber, and a 1.9F wire basket. RESULTS: The 2.0F NPL showed improved stone fragmentation efficiency compared to the 200mm laser (86 mg/min vs. 52 mg/min, p 1⁄4 0.014) as did the 3.6F NPL vs. the 365mm laser (173 mg/min vs. 80 mg/min, p1⁄40.05). The NPL created more 1-2 mm fragments, while the laser created more dust (< 1 mm fragments); the difference was more pronounced between the larger NPL and laser probes. In the 5 ureteroscopes tested, ureteroscope deflection was reduced by an average of 3.75 with the 2.0F NPL probe and 22.25 with the 2.4F NLP probe (compared to 5.25 with the laser and 2.75 with the basket). Irrigation flow through the ureteroscope was 36.5 ml/min on average, and was reduced to 18.3 ml/min with the 200mm laser fiber, and to 6.3 ml/min with the 2.0F NEP probe. CONCLUSIONS: The Nano-electric pulse Lithotripter produces improved stone fragmentation efficiency as compared to the holmium laser. However the 2.0F and 2.4F NPL probes limit flow and the 2.4F probe limits ureteroscope deflection.
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improving the lens design and performance of a contemporary electromagnetic shock wave Lithotripter
Proceedings of the National Academy of Sciences of the United States of America, 2014Co-Authors: Andreas Neisius, Walter Neal Simmons, Georgy Sankin, Nathan Smith, Nicholas J Kuntz, John F Madden, Daniel E Fovargue, Sorin Mitran, Michael E Lipkin, Glenn M PremingerAbstract:The efficiency of shock wave lithotripsy (SWL), a noninvasive first-line therapy for millions of nephrolithiasis patients, has not improved substantially in the past two decades, especially in regard to stone clearance. Here, we report a new acoustic lens design for a contemporary electromagnetic (EM) shock wave Lithotripter, based on recently acquired knowledge of the key Lithotripter field characteristics that correlate with efficient and safe SWL. The new lens design addresses concomitantly three fundamental drawbacks in EM Lithotripters, namely, narrow focal width, nonidealized pulse profile, and significant misalignment in acoustic focus and cavitation activities with the target stone at high output settings. Key design features and performance of the new lens were evaluated using model calculations and experimental measurements against the original lens under comparable acoustic pulse energy (E+) of 40 mJ. The −6-dB focal width of the new lens was enhanced from 7.4 to 11 mm at this energy level, and peak pressure (41 MPa) and maximum cavitation activity were both realigned to be within 5 mm of the Lithotripter focus. Stone comminution produced by the new lens was either statistically improved or similar to that of the original lens under various in vitro test conditions and was significantly improved in vivo in a swine model (89% vs. 54%, P = 0.01), and tissue injury was minimal using a clinical treatment protocol. The general principle and associated techniques described in this work can be applied to design improvement of all EM Lithotripters.
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a comparison of light spot hydrophone and fiber optic probe hydrophone for Lithotripter field characterization
Review of Scientific Instruments, 2012Co-Authors: Nathan Smith, Ralf Nanke, Jens Fehre, Walter Neal Simmons, Georgy Sankin, Pei ZhongAbstract:The performance of a newly developed light spot hydrophone (LSHD) in Lithotripter field characterization was compared to that of the fiber optic probe hydrophone (FOPH). Pressure waveforms produced by a stable electromagnetic shock wave source were measured by the LSHD and FOPH under identical experimental conditions. In the low energy regime, focus and field acoustic parameters matched well between the two hydrophones. At clinically relevant high energy settings for shock wave lithotripsy, the measured leading compressive pressure waveforms matched closely with each other. However, the LSHD recorded slightly larger |P–| (p < 0.05) and secondary peak compressive pressures (p < 0.01) than the FOPH, leading to about 20% increase in total acoustic pulse energy calculated in a 6 mm radius around the focus (p = 0.06). Tensile pulse durations deviated ∼5% (p < 0.01) due to tensile wave shortening from cavitation activity using the LSHD. Intermittent compression spikes and laser light reflection artifacts have been correlated to bubble activity based on simultaneous high-speed imaging analysis. Altogether, both hydrophones are adequate for Lithotripter field characterization as specified by the international standard IEC 61846.
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effect of Lithotripter focal width on stone comminution in shock wave lithotripsy
Journal of the Acoustical Society of America, 2010Co-Authors: Neal W Simmons, Georgy Sankin, Pei ZhongAbstract:Using a reflector insert, the original HM-3 Lithotripter field at 20 kV was altered significantly with the peak positive pressure (p+) in the focal plane increased from 49 to 87 MPa while the −6 dB focal width decreased concomitantly from 11 to 4 mm. Using the original reflector, p+ of 33 MPa with a −6 dB focal width of 18 mm were measured in a pre-focal plane 15-mm proximal to the Lithotripter focus. However, the acoustic pulse energy delivered to a 28-mm diameter area around the Lithotripter axis was comparable (∼120 mJ). For all three exposure conditions, similar stone comminution (∼70%) was produced in a mesh holder of 15 mm after 250 shocks. In contrast, stone comminution produced by the modified reflector either in a 15-mm finger cot (45%) or in a 30-mm membrane holder (14%) was significantly reduced from the corresponding values (56% and 26%) produced by the original reflector (no statistically significant differences were observed between the focal and pre-focal planes). These observations suggest...
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Interaction of Lithotripter shockwaves with single inertial cavitation bubbles
Journal of Fluid Mechanics, 2007Co-Authors: Evert Klaseboer, Georgy Sankin, Michael L Calvisi, Andrew J Szeri, Siew Wan Fong, Cary K. Turangan, Boo Cheong Khoo, Pei ZhongAbstract:: The dynamic interaction of a shockwave (modelled as a pressure pulse) with an initially spherically oscillating bubble is investigated. Upon the shockwave impact, the bubble deforms non-spherically and the flow field surrounding the bubble is determined with potential flow theory using the boundary-element method (BEM). The primary advantage of this method is its computational efficiency. The simulation process is repeated until the two opposite sides of the bubble surface collide with each other (i.e. the formation of a jet along the shockwave propagation direction). The collapse time of the bubble, its shape and the velocity of the jet are calculated. Moreover, the impact pressure is estimated based on water-hammer pressure theory. The Kelvin impulse, kinetic energy and bubble displacement (all at the moment of jet impact) are also determined. Overall, the simulated results compare favourably with experimental observations of Lithotripter shockwave interaction with single bubbles (using laser-induced bubbles at various oscillation stages). The simulations confirm the experimental observation that the most intense collapse, with the highest jet velocity and impact pressure, occurs for bubbles with intermediate size during the contraction phase when the collapse time of the bubble is approximately equal to the compressive pulse duration of the shock wave. Under this condition, the maximum amount of energy of the incident shockwave is transferred to the collapsing bubble. Further, the effect of the bubble contents (ideal gas with different initial pressures) and the initial conditions of the bubble (initially oscillating vs. non-oscillating) on the dynamics of the shockwave-bubble interaction are discussed.