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Isogai M, Hamamoto S, Kawase K, Okada T, Hattori T, Chaya R, Hamakawa T, Sugino T, Taguchi K, Umemoto Y, Okada A, Yasui T. Efficacy of ultrasound monitoring during extracorporeal shock wave lithotripsy: A multi‐institutional propensity score‐matched study. Int J Urol 2022; 29:1054-1060. [DOI: 10.1111/iju.14984] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Accepted: 06/30/2022] [Indexed: 11/30/2022]
Affiliation(s)
- Masahiko Isogai
- Department of Nephro‐Urology Nagoya City University Graduate School of Medical Sciences Nagoya Japan
- Department of Urology Nagoya City University West Medical Center Nagoya Japan
| | - Shuzo Hamamoto
- Department of Nephro‐Urology Nagoya City University Graduate School of Medical Sciences Nagoya Japan
| | - Kengo Kawase
- Department of Nephro‐Urology Nagoya City University Graduate School of Medical Sciences Nagoya Japan
| | - Tomoki Okada
- Department of Nephro‐Urology Nagoya City University Graduate School of Medical Sciences Nagoya Japan
| | - Tatsuya Hattori
- Department of Nephro‐Urology Nagoya City University Graduate School of Medical Sciences Nagoya Japan
| | - Ryosuke Chaya
- Department of Nephro‐Urology Nagoya City University Graduate School of Medical Sciences Nagoya Japan
| | - Takashi Hamakawa
- Department of Urology Nagoya City University West Medical Center Nagoya Japan
| | - Teruaki Sugino
- Department of Nephro‐Urology Nagoya City University Graduate School of Medical Sciences Nagoya Japan
| | - Kazumi Taguchi
- Department of Nephro‐Urology Nagoya City University Graduate School of Medical Sciences Nagoya Japan
| | - Yukihiro Umemoto
- Department of Urology Nagoya City University West Medical Center Nagoya Japan
| | - Atsushi Okada
- Department of Nephro‐Urology Nagoya City University Graduate School of Medical Sciences Nagoya Japan
| | - Takahiro Yasui
- Department of Nephro‐Urology Nagoya City University Graduate School of Medical Sciences Nagoya Japan
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Xiang G, Ma X, Liang C, Yu H, Liao D, Sankin G, Cao S, Wang K, Zhong P. Variations of stress field and stone fracture produced at different lateral locations in a shockwave lithotripter field. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2021; 150:1013. [PMID: 34470261 PMCID: PMC8357445 DOI: 10.1121/10.0005823] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
During clinical procedures, the lithotripter shock wave (LSW) that is incident on the stone and resultant stress field is often asymmetric due to the respiratory motion of the patient. The variations of the LSW-stone interaction and associated fracture pattern were investigated by photoelastic imaging, phantom experiments, and three-dimensional fluid-solid interaction modeling at different lateral locations in a lithotripter field. In contrast to a T-shaped fracture pattern often observed in the posterior region of the disk-shaped stone under symmetric loading, the fracture pattern gradually transitioned to a tilted L-shape under asymmetric loading conditions. Moreover, the model simulations revealed the generation of surface acoustic waves (SAWs), i.e., a leaky Rayleigh wave on the anterior boundary and Scholte wave on the posterior boundary of the stone. The propagation of SAWs on the stone boundary is accompanied by a progressive transition of the LSW reflection pattern from regular to von Neumann and to weak von Neumann reflection near the glancing incidence and, concomitantly, the development and growth of a Mach stem, swirling around the stone boundary. The maximum tensile stress and stress integral were produced by SAWs on the stone boundary under asymmetric loading conditions, which drove the initiation and extension of surface cracks into the bulk of the stone that is confirmed by micro-computed tomography analysis.
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Affiliation(s)
- Gaoming Xiang
- Department of Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina 27708, USA
| | - Xiaojian Ma
- Department of Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina 27708, USA
| | - Cosima Liang
- Department of Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina 27708, USA
| | - Hongyang Yu
- Department of Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina 27708, USA
| | - Defei Liao
- Department of Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina 27708, USA
| | - Georgy Sankin
- Department of Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina 27708, USA
| | - Shunxiang Cao
- Department of Aerospace and Ocean Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA
| | - Kevin Wang
- Department of Aerospace and Ocean Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA
| | - Pei Zhong
- Department of Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina 27708, USA
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Rassweiler JJ, Rassweiler-Seyfried MC. Therapieverfahren – extrakorporale Stoßwellentherapie. Urolithiasis 2021. [DOI: 10.1007/978-3-662-62454-8_6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Reynolds LF, Kroczak T, Pace KT. Indications and contraindications for shock wave lithotripsy and how to improve outcomes. Asian J Urol 2018; 5:256-263. [PMID: 30364729 PMCID: PMC6197584 DOI: 10.1016/j.ajur.2018.08.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Revised: 05/24/2018] [Accepted: 06/19/2018] [Indexed: 12/25/2022] Open
Abstract
For over 35 years shock wave lithotripsy has proven to be an effective, safe and truly minimally invasive option for the treatment of nephrolithiasis. Various technical factors as well as patient selection can impact the success of the procedure. We used published work focusing on outcomes of shock wave lithotripsy, risk of complications, and strategies for improving stone fragmentation to create this review. Multiple patient and technical factors have been found to impact success of treatment. Skin to stone distance, stone density and composition, size and location of the stone within the urinary system all influence stone free rates. A slower rate with a gradual increasing voltage, precise targeting, proper coupling will improve stone fragmentation and decrease risk of complications. The selection of appropriate patients through a shared decision making process and attention to the technical factors that improve stone free rates is key to providing an effective treatment and patient satisfaction.
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Affiliation(s)
| | | | - Kenneth T. Pace
- Division of Urology, St. Michael's Hospital, Toronto, Canada
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Ultrasonography Is Not Inferior to Fluoroscopy to Guide Extracorporeal Shock Waves during Treatment of Renal and Upper Ureteric Calculi: A Randomized Prospective Study. BIOMED RESEARCH INTERNATIONAL 2017; 2017:7802672. [PMID: 28589147 PMCID: PMC5447263 DOI: 10.1155/2017/7802672] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Accepted: 03/29/2017] [Indexed: 12/23/2022]
Abstract
Objective To investigate whether the visualization modality (ultrasound or fluoroscopy) used during shockwave lithotripsy (SWL) affects the clinical outcome in those instances where both imaging modalities are optional. Methods Between November 2014 and July 2016, 114 patients with radiopaque upper urinary tract calculi were randomly assigned to an ultrasound- or fluoroscopy-guided SWL group in a prospective, open-label, single-center study. A standardized SWL protocol was used. The stone-free rate and the positive outcome rate (stone-free or asymptomatic residual fragments ≤ 4 mm) were compared. Results The stone-free rate was 52% in the ultrasound-guided group compared to 42% in the fluoroscopy-guided group (p = 0.06) and the positive outcome rate was 79% in the ultrasound-guided group compared to 70% in the fluoroscopy-guided group (p = 0.28). These results were not significantly different but proved to be noninferior based on a Wilson confidence interval of independent proportions (noninferiority limit 10%). The mean number of SWL sessions was not significantly different (p = 0.4). Conclusion Our study demonstrated that the clinical results of ultrasound-guided SWL were not inferior to the results of fluoroscopy-guided SWL, while no ionizing radiation is needed.
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Neisius A, Lipkin ME, Rassweiler JJ, Zhong P, Preminger GM, Knoll T. Shock wave lithotripsy: the new phoenix? World J Urol 2014; 33:213-21. [PMID: 25081010 DOI: 10.1007/s00345-014-1369-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2014] [Accepted: 07/18/2014] [Indexed: 11/29/2022] Open
Abstract
INTRODUCTION Following its introduction in 1980, shock wave lithotripsy (SWL) rapidly emerged as the first-line treatment for the majority of patients with urolithiasis. Millions of SWL therapies have since been performed worldwide, and nowadays, SWL still remains to be the least invasive therapy modality for urinary stones. During the last three decades, SWL technology has advanced in terms of shock wave generation, focusing, patient coupling and stone localization. The implementation of multifunctional lithotripters has made SWL available to urology departments worldwide. Indications for SWL have evolved as well. Although endoscopic treatment techniques have improved significantly and seem to take the lead in stone therapy in the western countries due to high stone-free rates, SWL continues to be considered as the first-line therapy for the treatment of most intra-renal stones and many ureteral stones. METHODS This paper reviews the fundamentals of SWL physics to facilitate a better understanding about how a lithotripter works and should be best utilized. RESULTS Advances in lithotripsy technology such as shock wave generation and focusing, advances in stone localization (imaging), different energy source concepts and coupling modalities are presented. Furthermore adjuncts to improve the efficacy of SWL including different treatment strategies are reviewed. CONCLUSION If urologists make use of a more comprehensive understanding of the pathophysiology and physics of shock waves, much better results could be achieved in the future. This may lead to a renaissance and encourage SWL as first-line therapy for urolithiasis in times of rapid progress in endoscopic treatment modalities.
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Affiliation(s)
- Andreas Neisius
- Department of Urology, Universitätsmedizin Mainz, Johannes Gutenberg University, Langenbeckstrasse 1, Mainz, Germany,
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Abstract
Even 32 years after its first introduction shockwave lithotripsy (SWL) remains a matter of discussion and controversy. Since the first SWL in 1980, millions of treatments have been performed worldwide. To this day SWL remains the least invasive of all stone treatments and is considered the treatment modality of first choice for the majority of urinary stones. Despite the massive scale on which SWL is performed in a wide range of indications, complication rate has always remained very low and usually limited to minor side effects and complications. The introduction of affordable multifunctional lithotripters has made SWL available to more and more departments of urology worldwide. Still many centers are disappointed with the treatment results and concerned about the adverse tissue effects. In this SWL proves to be the victim of its uninvasiveness and its apparent ease of practice. Urologists need proper skill and experience; however, to adequately administer shockwaves in order to improve outcome. This aspect is too often minimized and neglected. Apart from this the power of shockwaves often is underestimated by operators of shockwave machines. Basic knowledge of the physics of shockwaves could further reduce the already minimal adverse tissue effects. Good training and coaching in the administration of shockwaves would no doubt lead to a renaissance of SWL with better treatment results and minimal adverse tissue effects.
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Affiliation(s)
- Geert G Tailly
- Department of Urology, AZ klina, Augustijnslei, Brasschaat, Belgium
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Chang CC, Pu YR, Manousakas I, Liang SM, Yu FM, Tong YC, Lin SH. In vitro study of the revised ultrasound based real-time tracking of renal stones for shock wave lithotripsy: Part 1. J Urol 2012. [PMID: 23201381 DOI: 10.1016/j.juro.2012.11.111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
PURPOSE Extracorporeal shock wave lithotripsy has been popular since the 1980s. Only 30% to 50% of the shock waves of all conventional lithotripters are focused on stones. We developed an ultrasound based, real-time stone tracking system (version 1) to improve accuracy and treatment efficiency. However, some problems remained. We revised the existing system (version 2) and tested its reliability and performance. MATERIALS AND METHODS We revised the system by adding more algorithms to decrease renal stone misidentification. We verified the advanced system by 2 tests using no tracking and tracking with 13 stone trajectories for versions 1 and 2. We performed the coincidence test to evaluate the accuracy of targeting the stone within the effective focal area and the stone fragmentation efficiency test to clarify the decrease in the number of shocks needed for stone fragmentation. RESULTS In the coincidence test the mean ± SD results of the nontracking system, and tracking versions 1 and 2 were 68.8% ± 18.8%, 89.9% ± 5.2% and 94.3% ± 4.5%, respectively. Version 2 was statistically significantly better than version 1 (p = 1.5 × 10(-4)). In the stone fragmentation efficiency test the mean results of the nontracking system, and versions 1 and 2 were 49.5% ± 14.2%, 85.1% ± 4.5% and 89.5% ± 4.2%, respectively. Version 2 was statistically significantly better than version 1 (p = 1.9 × 10(-8)). CONCLUSIONS The revised tracking system is better than version 1. It improves treatment efficiency, decreases stone misidentification and can shorten treatment time.
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Affiliation(s)
- Chien-Chen Chang
- Department of Urology, National Cheng Kung University Hospital, College of Medicine, Tainan, Taiwan
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Bhojani N, Lingeman JE. Shockwave lithotripsy-new concepts and optimizing treatment parameters. Urol Clin North Am 2012. [PMID: 23177635 DOI: 10.1016/j.ucl.2012.09.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The treatment of kidney stone disease has changed dramatically over the past 30 years. This change is due in large part to the arrival of extracorporeal shock wave lithotripsy (ESWL). ESWL along with the advances in ureteroscopic and percutaneous techniques has led to the virtual extinction of open surgical treatments for kidney stone disease. Much research has gone into understanding how ESWL can be made more efficient and safe. This article discusses the parameters that can be used to optimize ESWL outcomes as well as the new concepts that are affecting the efficacy and efficiency of ESWL.
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Affiliation(s)
- Naeem Bhojani
- Department of Urology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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Sorensen MD, Bailey MR, Shah AR, Hsi RS, Paun M, Harper JD. Quantitative assessment of shockwave lithotripsy accuracy and the effect of respiratory motion. J Endourol 2012; 26:1070-4. [PMID: 22471349 DOI: 10.1089/end.2012.0042] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND AND PURPOSE Effective stone comminution during shockwave lithotripsy (SWL) is dependent on precise three-dimensional targeting of the shockwave. Respiratory motion, imprecise targeting or shockwave alignment, and stone movement may compromise treatment efficacy. The purpose of this study was to evaluate the accuracy of shockwave targeting during SWL treatment and the effect of motion from respiration. PATIENTS AND METHODS Ten patients underwent SWL for the treatment of 13 renal stones. Stones were targeted fluoroscopically using a Healthtronics Lithotron (five cases) or Dornier Compact Delta II (five cases) shockwave lithotripter. Shocks were delivered at a rate of 1 to 2 Hz with ramping shockwave energy settings of 14 to 26 kV or level 1 to 5. After the low energy pretreatment and protective pause, a commercial diagnostic ultrasound (US) imaging system was used to record images of the stone during active SWL treatment. Shockwave accuracy, defined as the proportion of shockwaves that resulted in stone motion with shockwave delivery, and respiratory stone motion were determined by two independent observers who reviewed the ultrasonographic videos. RESULTS Mean age was 51 ± 15 years with 60% men, and mean stone size was 10.5 ± 3.7 mm (range 5-18 mm). A mean of 2675 ± 303 shocks was delivered. Shockwave-induced stone motion was observed with every stone. Accurate targeting of the stone occurred in 60% ± 15% of shockwaves. CONCLUSIONS US imaging during SWL revealed that 40% of shockwaves miss the stone and contribute solely to tissue injury, primarily from movement with respiration. These data support the need for a device to deliver shockwaves only when the stone is in target. US imaging provides real-time assessment of stone targeting and accuracy of shockwave delivery.
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Affiliation(s)
- Mathew D Sorensen
- Department of Urology, University of Washington School of Medicine, Seattle, Washington 98195, USA.
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Shock wave technology and application: an update. Eur Urol 2011; 59:784-96. [PMID: 21354696 DOI: 10.1016/j.eururo.2011.02.033] [Citation(s) in RCA: 166] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2011] [Accepted: 02/15/2011] [Indexed: 11/22/2022]
Abstract
CONTEXT The introduction of new lithotripters has increased problems associated with shock wave application. Recent studies concerning mechanisms of stone disintegration, shock wave focusing, coupling, and application have appeared that may address some of these problems. OBJECTIVE To present a consensus with respect to the physics and techniques used by urologists, physicists, and representatives of European lithotripter companies. EVIDENCE ACQUISITION We reviewed recent literature (PubMed, Embase, Medline) that focused on the physics of shock waves, theories of stone disintegration, and studies on optimising shock wave application. In addition, we used relevant information from a consensus meeting of the German Society of Shock Wave Lithotripsy. EVIDENCE SYNTHESIS Besides established mechanisms describing initial fragmentation (tear and shear forces, spallation, cavitation, quasi-static squeezing), the model of dynamic squeezing offers new insight in stone comminution. Manufacturers have modified sources to either enlarge the focal zone or offer different focal sizes. The efficacy of extracorporeal shock wave lithotripsy (ESWL) can be increased by lowering the pulse rate to 60-80 shock waves/min and by ramping the shock wave energy. With the water cushion, the quality of coupling has become a critical factor that depends on the amount, viscosity, and temperature of the gel. Fluoroscopy time can be reduced by automated localisation or the use of optical and acoustic tracking systems. There is a trend towards larger focal zones and lower shock wave pressures. CONCLUSIONS New theories for stone disintegration favour the use of shock wave sources with larger focal zones. Use of slower pulse rates, ramping strategies, and adequate coupling of the shock wave head can significantly increase the efficacy and safety of ESWL.
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Bohris C, Bayer T, Gumpinger R. Ultrasound monitoring of kidney stone extracorporeal shockwave lithotripsy with an external transducer: does fatty tissue cause image distortions that affect stone comminution? J Endourol 2010; 24:81-8. [PMID: 19961334 DOI: 10.1089/end.2009.0158] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
INTRODUCTION Ultrasound imaging, using either an inline or an external transducer, is a standard method for extracorporeal shockwave lithotripsy (SWL) monitoring. This study investigates whether image distortions caused by the low sound speed of fatty tissue could lead to incorrect stone positioning such that disintegration is affected. MATERIALS AND METHODS To define the accuracy needed for SWL monitoring, the dependency of fragmentation efficiency on the distance between stone center and SWL focus was examined by in vitro model stone tests. In a clinical study, 15 patients with kidney stones were treated with a Dornier Sigma FarSight. This lithotripter was equipped with both an inline and an external transducer. They were operated alternately to check for inconsistencies, which would indicate ultrasound image distortions. In addition, the ultrasound paths from the transducer to the SWL focus were analyzed for error estimation. RESULTS AND DISCUSSION In the model stone tests, the number of shock waves required for complete fragmentation doubled if the stone was about 7.5 to 10 mm off focus in lateral direction. In the clinical trial, the stone positions obtained from an inline and an external transducer coincided within a 5 mm range of tolerance, but that approach suffered from some practical difficulties, resulting in measurement imprecision. The sound path analysis showed that the lengths through fatty tissue were too short to result in significant image distortion. The body mass index (20-31 kg/m(2)) was representative, except for very obese patients. Additional confirmation of correct stone positioning could be achieved quite easily by looking for pixel movement in the B-mode image or employing Doppler hit/miss monitoring. CONCLUSION Within the study group, no image distortion caused by fatty tissue that could be clinically relevant for SWL was observed.
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Lingeman JE, McAteer JA, Gnessin E, Evan AP. Shock wave lithotripsy: advances in technology and technique. Nat Rev Urol 2009; 6:660-70. [PMID: 19956196 PMCID: PMC2923385 DOI: 10.1038/nrurol.2009.216] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Shock wave lithotripsy (SWL) is the only noninvasive method for stone removal. Once considered as a primary option for the treatment of virtually all stones, SWL is now recognized to have important limitations that restrict its use. In particular, the effectiveness of SWL is severely limited by stone burden, and treatment with shock waves carries the risk of acute injury with the potential for long-term adverse effects. Research aiming to characterize the renal response to shock waves and to determine the mechanisms of shock wave action in stone breakage and renal injury has begun to suggest new treatment strategies to improve success rates and safety. Urologists can achieve better outcomes by treating at slower shock wave rate using a step-wise protocol. The aim is to achieve stone comminution using as few shock waves and at as low a power level as possible. Important challenges remain, including the need to improve acoustic coupling, enhance stone targeting, better determine when stone breakage is complete, and minimize the occurrence of residual stone fragments. New technologies have begun to address many of these issues, and hold considerable promise for the future.
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Affiliation(s)
- James E Lingeman
- Methodist Hospital Institute for Kidney Stone Disease, Indianapolis, IN, USA.
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Owen NR, Bailey MR, Crum LA, Sapozhnikov OA, Trusov LA. The use of resonant scattering to identify stone fracture in shock wave lithotripsy. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2007; 121:EL41-7. [PMID: 17297825 DOI: 10.1121/1.2401266] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
There is currently little feedback as to whether kidney stones have fractured during shock wave lithotripsy. Resonant scattering of the lithotripter shock wave was used here to differentiate intact and fractured stone models in water. Scattering, including reflection and radiation due to reverberation from within the stone, was calculated numerically with linear elasticity theory and agreed well with measurements made with a focused receiver. Identification of fracture was possible through frequency analysis, where scatter from fractured stones was characterized by higher energy in distinct bands. High-speed photography concurrent with measurement indicated the effect was not due to cavitation.
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Bohris C, Jensen H, Bayer T, Liong ML. A New Integrated Ultrasound System for Shockwave Lithotripsy. J Endourol 2006; 20:863-9. [PMID: 17144852 DOI: 10.1089/end.2006.20.863] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND AND PURPOSE Inline ultrasound monitoring requires good image quality for accurate stone localization, as well as low shockwave shadowing and a robust transducer. In general, conventional transducers designed for another purpose, such as abdominal scanning, are employed. The distance between the transducer and the SWL focus can be varied by a mechanical drive. The drawback is reduced fragmentation at short distances and poor imaging at long distances. This paper introduces a new approach using a specially designed transducer without a mechanical drive. MATERIALS AND METHODS A transducer prototype with optimized beam focusing (B-K Medical, Herlev, Denmark) was integrated into a modified Compact Delta II therapy head (Dornier MedTech, Wessling, Germany). Image quality was tested at two clinical sites, where 40 kidney and 14 ureteral stones were treated. The shockwave was characterized by model stone tests and fiberoptic hydrophone measurements. RESULTS Both kidney and ureteral stone treatments could be monitored reliably. Despite the long distance to the SWL focus, the transducer could be operated with relatively high frequencies (3.5-6 MHz), so that high image resolution was obtained. Model stone tests yielded the same fragmentation as the standard Compact Delta II without a transducer. CONCLUSIONS This study shows that the concept of an integrated transducer distant from the shockwave focus is feasible. Transducer elevation, which is accompanied by shockwave shadowing and early transducer failure, is avoided by employing a dedicated transducer design.
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Affiliation(s)
- C Chaussy
- Klinik für Urologie, Klinikum Harlaching, Städtisches Klinikum München GmbH, Sanatoriumsplatz 2, 81545 München.
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