Electrohydraulic Lithotripter Research Articles

Effect of targeting and generator type on efficacy of extracorporeal shock wave lithotripsy.

Analysis of the effect of technical factors, i.e. the type of stone targeting and shock wave generator, on ESWL efficacy. Evaluation of secondary outcomes to determine an optimal strategy for performing the procedure. In the period from 01/2016 to 07/2021, we analyzed data from patients indicated for ESWL for nephrolithiasis and proximal or distal ureterolithiasis. This was a tricenter retrospective study to evaluate stone-free rates (SFR) while taking into account the number of ESWL sessions in four selected groups of patients with comparable characteristics. A patient is considered stone-free in the absence of residual lithiasis or with an asymptomatic residue of up to 2 mm. The real-time ultrasound-guided (USG) arm consisted of a group of 120 patients on the electromagnetic STORZ SLK lithotripter in the period from 02/2017 to 02/2020. A total of three comparison arms with x-ray guidance were created: A: 68 patients between 01/2016 and 03/2017 on the Medilit 7 electrohydraulic lithotripter. B: 72 patients from 04/2017 to 10/2017 on the Sonolith i-sys electroconductive lithotripter (EDAP). C: 120 patients from 03/2018 to 07/2021 on the STORZ SLK electromagnetic lithotripter. By comparing the US and x-ray guidance using the STORZ SLK lithotripter, the effect of targeting when using an identical device (electromagnetic generator) was evaluated. By comparing the arms A, B, and C, the efficacy in different types of generators - electromagnetic, electroconductive, electrohydraulic - was assessed when the same type of targeting (fluoroscopy) was used. The secondary parameters that were monitored included: the rate of use of auxiliary techniques in stone management; radiation exposure for the patient and/or operator; analgesic consumption; and the time required to perform the procedure. When US versus x-ray guidance was compared in an electromagnetic lithotripter, SFRs of 90% vs. 85% (P=0.329), i.e. statistically comparable results, were obtained. By comparing electromagnetic, electroconductive, and electrohydraulic generators with fluoroscopy, SFRs of 85%, 88.9%, and 88.2% were obtained, respectively (P=0.727). When the degree of need for intraoperative analgesic administration was assessed, the electromagnetic generator was found to have a significantly lower consumption (20.8% vs. 30.6% vs. 48.5%) (P=0.0005). Values less than 1095 HU and 108.5 mm were shown to be optimal cut-off values for stone density and skin-to-stone distance, respectively. Based on our comparative analysis, the noninferiority of US stone targeting was demonstrated compared to fluoroscopic targeting. No significant differences in ESWL efficacy were found using electrohydraulic, electroconductive or electromagnetic shock wave generators. With the electromagnetic lithotripter, there was a significantly lower analgesic consumption than with the electrohydraulic type.

Is there a place for extracorporeal shockwave lithotripsy (ESWL) in the endoscopic era?

This retrospective study aimed to evaluate whether there was still a place for ESWL therapy in the endourological era. From 1988 to 2018, ESWL therapy was performed with 3 successive types of lithotripters in our hospital. From 1988 to 1998, the electrohydraulic lithotripter NS-15 was used, and the electromagnetic lithotripter HK-V was put to use in 1999. Since 2010, the electromagnetic lithotripter HK-Vm has been used. Over the 30-year period, 16,969 urolithiasis patients underwent ESWL therapy, including 124 paediatric cases and 178 special cases. The stone clearance rate (SCR) and postoperative complications in the 3 lithotripter groups were recorded and analysed. The SCR was estimated by ultrasonography or plain X-ray, while the complications were recorded by the modified Clavien grading system. The primary stone clearance rate (pSCR) of ureteral and renal stones was significantly improved in the HK-Vm group compared with the NS-15 and HK-V groups. The final stone clearance rate (fSCR) of lower calyx stones was considerably higher in the HK-Vm group (55.9%) than in the NS-15 (41.1%) and HK-V (44.1%) groups. Most complications were grade I and II, while the incidence of grade III and above complications was less than 3%. Additionally, the fSCR in paediatric and special cases ranged from 66.5% to 83.5%, with no record of severe complications. As our data showed, ESWL was effective and safe for most urolithiasis patients, including paediatric patients and special cases. Therefore, ESWL is still the major treatment option in the current endourological era.

Stone technology: intracorporeal lithotripters.

Intracorporeal lithotripsy is becoming the most commonly used surgical method of stone treatment in Urology. The five major types of intracorporeal lithotripters are ultrasonic, ballistic, and combination lithotripters as well as laser and electrohydraulic lithotripters. The advantages and disadvantages of choosing each of these treatment modalities are reviewed. Extensive review of literature was performed to identify the types of intracorporeal lithotripters. An investigation was undertaken of the early development of each modality of intracorporeal lithotripsy and/or the mechanism of action. Challenges of each technique were identified and presented. Finally, a determination was made of how these lithotripters compare on the basis of effectiveness of action and cost based on information provided in primary literature as well as previous reviews of these modalities. Contemporary lithotripters have found widespread use in the management of urinary lithiasis. Holmium laser lithotripsy has become one of the most commonly used tools for intracorporeal lithotripsy. There is a wide variety of intracorporeal lithotripters which can be chosen based on the characteristics of each modality and the requirements of the urologist.

The Respiratory Induced Kidney Motion: Does It Really Effect the Shock Wave Lithotripsy?

To investigate the effect of respiratory induced kidney mobility on success of shock wave lithotripsy (SWL) with an electrohydraulic lithotripter. Between May 2013 and April 2015, 158 patients underwent SWL treatment for kidney stones with an electrohydraulic lithotripter. The exclusion criteria were presence of a known metabolic disease (such as cystinuria), non-opaque stones, need for focusing with ultrasonography, abnormal habitus, urinary tract abnormalities, and inability to tolerate SWL until the end of the procedure. Stones greater than 20 mm, and lower pole stones were also excluded. The movement of the kidneys were measured with fluoroscopy guidance. The procedure was successful in 66.7% of the males, and 56.9% of the females. The mean stone size was 11 ± 3 mm in the successful group, and it was 14 ± 4 mm in the unsuccessful group. The mean stone mobility rate was 32 ± 10 in the successful group and 40 ± 11 in the unsuccessful group. Multivariate analysis showed that stone size and kidney mobility affected the success rate significantly, however Hounsfield Unit (HU) did not. The current study shows the significant effect of kidney motion on the success of SWL. Further studies with different lithotripters are needed to determine the significance of kidney mobility.

Multiphase fluid-solid coupled analysis of shock-bubble-stone interaction in shockwave lithotripsy.

A novel multiphase fluid-solid-coupled computational framework is applied to investigate the interaction of a kidney stone immersed in liquid with a lithotripsy shock wave (LSW) and a gas bubble near the stone. The main objective is to elucidate the effects of a bubble in the shock path to the elastic and fracture behaviors of the stone. The computational framework couples a finite volume 2-phase computational fluid dynamics solver with a finite element computational solid dynamics solver. The surface of the stone is represented as a dynamic embedded boundary in the computational fluid dynamics solver. The evolution of the bubble surface is captured by solving the level set equation. The interface conditions at the surfaces of the stone and the bubble are enforced through the construction and solution of local fluid-solid and 2-fluid Riemann problems. This computational framework is first verified for 3 example problems including a 1D multimaterial Riemann problem, a 3D shock-stone interaction problem, and a 3D shock-bubble interaction problem. Next, a series of shock-bubble-stone-coupled simulations are presented. This study suggests that the dynamic response of a bubble to LSW varies dramatically depending on its initial size. Bubbles with an initial radius smaller than a threshold collapse within 1μs after the passage of LSW, whereas larger bubbles do not. For a typical LSW generated by an electrohydraulic lithotripter (pmax =35.0MPa, pmin =-10.1MPa), this threshold is approximately 0.12mm. Moreover, this study suggests that a noncollapsing bubble imposes a negative effect on stone fracture as it shields part of the LSW from the stone. On the other hand, a collapsing bubble may promote fracture on the proximal surface of the stone, yet hinder fracture from stone interior.

Extracorporeal shock wave lithotripsy in infants less than 12-month old.

There is a lack of literature on children compared to adults regarding the long-term effects of extracorporeal shock wave lithotripsy (SWL), specifically in infants. The aim of the present study was to analyze the efficacy and safety of SWL in infants and also evaluate its potential adverse effects in the mid-term. Between May 1999 and December 2013, 36 infants with 39 renal units underwent SWL treatment for kidney stones with an electrohydraulic lithotripter (Dornier MPL 9000/ELMED Multimed Classic). All children were less than 12-month old. The mid-term effects of SWL were examined at the last follow-up by measuring arterial blood pressure, random blood glucose level and ipsilateral kidney size. Evaluation of treatment and its consequences was based on clinical examination, blood tests and conventional imaging (plain abdominal radiography and ultrasound). Overall stone-free rate was 84.6% after 3-month follow-up without any major complications. Mid-term follow-up was available in 20 of 36 children with a mean follow-up of 3.2±2.8years (range 0.5-15.3). None of the infants were found to develop new onset of hypertension or diabetes. All treated infant kidneys' sizes were in the normal percentile range. SWL for management of infant kidney stones is effective and safe in the mid-term.

Renal Stones Outlet Obstructed by Pararenal Pelvic Cyst Management

s / Urological Science 26 (2015) S50eS81 S54 plane abdominal X-ray. Treatment outcomes, including disintegration rate, stone-free rate, and retreatment rate, for both groups were also compared. Results: Pre-SWL, the patient characteristics, treatment parameters, and stone-related parameter were similar for both groups. There were higher stone-free and disintegration rates in the electrohydraulic group for most stones, but the retreatment rate was higher in the electromagnetic group. There was no significant difference for stones at the middle and lower ureter and stones in the ureter bigger than 1 cm. The complication rates for pain, skin, or subcapsular hematoma were not significantly different between groups. Conclusion: The electrohydraulic lithotriptor (Medispec E3000) group has significantly higher disintegration and stone-free rates, but has similar complication rates compared to the electromagnetic lithotriptor (Medispec EM1000) group. There is no significant difference between the two groups for middle or lower ureteral stones and ureteral stones bigger than 1 cm. The electromagnetic lithotripter has the advantage of being useful for SWL even without anesthesia. NDP017: RENAL STONES OUTLET OBSTRUCTED BY PARARENAL PELVIC CYST MANAGEMENT Ping-Ju Tsai, Cheng-Chen Su, Chung-Sung Shen, Shih-Ya Hung. Division of Urology, Department of Surgery, Yuan's General Hospital, Kaohsiung, Taiwan We often incidentally indentified some renal cysts at OPD. The principles of non-obstructive simple renal cysts management is watchful waiting. However, some renal cysts need to be managed, such as malignancy tendency, renal pelvic-ureteral junction obstruction by those cysts. The management of renal cysts included aspiration combined with injection of scloerosing materials, and laparoscopic unroofing. We presented a 60-year-old male who has multiple low calyceal stones with focal hydrocalyx. The renal pelvic-ureteral junction was extrinsic compressed by one large parapelvic renal cyst. First, non-enhanced abdominal CT scan was arranged and thus we clearly know the relative locations of cyst and pelvic-ureteral junction. Laparoscopic unroofing of renal cyst was performed. After surgery, we arranged intravenous pyelogram for confirming the pelvic-ureteral junction patency. Watchful waiting for spontaneous passage of multiple small renal stones was planned. Unfortunately, stone streets formations in low third and upper third ureter were found later. Ureteroscopic lithotripsy and double-J catheter were performed smoothly. Extraperitoneal shock wave for residual renal stones was performed, too. Last, we removed the double-J catheter. The clearance of renal stone was excellent.

Lithotripter Outcomes in a Community Practice Setting: Comparison of an Electromagnetic and an Electrohydraulic Lithotripter

We assessed patient outcomes using 2 widely different contemporary lithotripters. We performed a consecutive case series study of 355 patients in a large private practice group using a Modulith® SLX electromagnetic lithotripter in 200 patients and a LithoGold LG-380 electrohydraulic lithotripter (TRT, Woodstock, Georgia) in 155. Patients were followed at approximately 2 weeks. All preoperative and postoperative films were reviewed blindly by a dedicated genitourinary radiologist. The stone-free rate was defined as no residual fragments remaining after a single session of shock wave lithotripsy without an ancillary procedure. Patients with multiple stones were excluded from analysis, leaving 76 and 142 treated with electrohydraulic and electromagnetic lithotripsy, respectively. The stone-free rate was similar for the electrohydraulic and electromagnetic lithotripters (29 of 76 patients or 38.2% and 69 of 142 or 48.6%, p = 0.15) with no difference in the stone-free outcome for renal stones (20 of 45 or 44.4% and 33 of 66 or 50%, p = 0.70) or ureteral stones (9 of 31 or 29% and 36 of 76 or 47.4%, respectively, p = 0.08). The percent of stones that did not break was similar for the electrohydraulic and electromagnetic devices (10 of 76 patients or 13.2% and 23 of 142 or 16.2%) and ureteroscopy was the most common ancillary procedure (18 of 22 or 81.8% and 30 of 40 or 75%, respectively). The overall mean number of procedures performed in patients in the 2 groups was similar (1.7 and 1.5, respectively). We present lithotripsy outcomes in the setting of a suburban urology practice. Stone-free rates were modest using shock wave lithotripsy alone but access to ureteroscopy provided satisfactory outcomes overall. Although the acoustic characteristics of the electrohydraulic and electromagnetic lithotripters differ substantially, outcomes with these 2 machines were similar.

Comparable clinical outcomes with two lithotripters having substantially different acoustic characteristics

A consecutive case study was conducted to assess the clinical performance of the Lithogold, an electrohydraulic lithotripter having a relatively low P + and broad focal width (FW) (~20 MPa, ~20 mm), and the electromagnetic Storz-SLX having higher P + and narrower FW (~50 MPa, 3–4 mm). Treatment was at 60 SW/min with follow-up at ~2 weeks. Stone free rate (SFR) was defined as no residual fragments remaining after single session SWL. SFR was similar for the two lithotripters (Lithogold 29/76 = 38.2%; SLX 69/142 = 48.6% p = 0.15), with no difference in outcome for renal stones (Lithogold 20/45 = 44.4%; SLX 33/66 = 50%, p = 0.70) or stones in the ureter (Lithogold 9/31 = 29%; SLX 36/76 = 47.4%, p = 0.08). Stone size did not differ between the two lithotripters for patients who were not stone free (9.1±3.7 mm for Lithogold vs. 8.5±3.5 mm for SLX, P = 0.42), but the stone-free patients in the Lithogold group had larger stones on average than the stone-free patients treated with the SLX (7.6±2.5 mm vs. 6.2±3.2 mm, P = 0.005). The percentage of stones that did not break was similar (Lithogold 10/76 = 13.2%; SLX 23/142 = 16.2%). These data present a realistic picture of clinical outcomes using modern lithotripters, and although the acoustic characteristics of the Lithogold and SLX differ considerably, outcomes were similar. [NIH-DK43881.]

Pediatric Extracorporeal Shock Wave Lithotripsy: Multi-Institutional Results

To evaluate the efficacy, auxiliary procedures and complications of pediatric extracorporeal shock wave lithotripsy (ESWL) performed with electrohydraulic lithotripters. Children with urolithiasis, aged between 0 and 15, were retrospectively evaluated. ESWL was performed by using two different electrohydraulic lithotripters, Elmed Multimed Classic (Elmed Medical Systems, Ankara, Turkey) and E-1000 (EMD Medical Systems, Ankara, Turkey), between January 2008 and December 2012 in four different referral centers in Turkey. 85.5% of patients were stone-free at 3 months. Further ESWL treatment was needed in 33.7% of the cases (one session, n = 55; two sessions, n = 15; three sessions, n = 13). Steinstrasse occurred in 10 patients but 8 of them cleared completely during the follow-up period. Urinary tract infection was detected in 3 (3.9%), fever in 3 (3.9%) and a small subcapsular hematoma in one (1.3%) patient, respectively. When the stones were divided into two groups as those with diameters <10 mm and ≥10 mm, it was found that the stone-free rate was associated with stone diameter, and that the smaller diameters had higher but statistically insignificant stone-free rates (P = 0.196). ESWL yields favorable results with low rates of complication and auxiliary procedures in selected pediatric patients.

Investigation of Differences Between Nanosecond Electropulse and Electrohydraulic Methods of Lithotripsy: A ComparativeIn VitroStudy of Efficacy

To compare the effectiveness of novel nanosecond electropulse lithotripsy with standard electrohydraulic lithotripsy to demonstrate and authenticate their differences because both modalities appear to be similar. An in vitro fragmentation study was conducted using cuboid BegoStone phantoms, which mimic hard and soft stones, based on an established model. Three different stone sizes were used in the testing having volumes of 100, 256, and 320 mm(3). A nanosecond electropulse lithotripter (NEPL) and an electrohydraulic lithotripter (EHL) were operated using a range of probe sizes at comparable energy settings and pulse rates with the objective of obtaining a stone fragment <2 mm. To compare the efficacy of these two lithotripters, the number of pulses needed for stone phantom fragmentation was recorded according to probe size and energy setting, which were then converted into units of cumulative energy. The results clearly demonstrated that, for all operating modes and stone phantom types, the NEPL device needs much less cumulative energy and thus fewer pulses and consequently less time to achieve stone fragmentation than the EHL device. The disparity in the results is explained by the dissimilar mechanisms at work in the compared lithotripters during destruction of the stone. The electropulse stone disintegration mechanism transfers energy directly into the stone because of discharge penetration into a solid body. This contrasts with the electrohydraulic mechanism in EHL in which energy is transferred through the liquid medium, which also creates a damaging shockwave. The findings demonstrate that, for all operating modes and stone types, the NEPL device needs much less cumulative energy and thus fewer pulses for stone fragmentation than the EHL device. The disparity in the results is explained by the dissimilar mechanisms at work in the compared lithotripters during destruction of the stone.

Acoustic characterization and assessment of renal injury with a broad focal width electrohydraulic lithotripter

This study provides an independent assessment of a novel lithotripter (LG-380, Tissue Regeneration Technologies), marketed as having a long-life self-adjusting spark gap electrode and producing a low-pressure, broad-focal-zone acoustic field. For acoustic characterization we coupled the therapy head of the lithotripter to a water tank and mapped the field using a fiber-optic hydrophone (FOPH-500, RP Acoustics). At the target point of the lithotripter, the peak positive pressure (P +) remained relatively stable (~19±5 MPa at power level 9) during the 6000 shock waves (SWs) lifetime of the electrode. The position of maximum P + (~35 MPa at PL9) was 35mm distal to target point and shifted progressively toward the therapy head as the electrode aged, reaching the target point (while reducing to P + ~20 MPa) after ~5000 SWs. This was likely due to a slight movement in position of the self-adjusting spark gap—changing the focus of the shock wave and the dimensions of the focal volume of the lithotripter. Kidney injury was assessed using an established pig model by routine measures of renal function and quantitation of lesion size. Simulated clinical treatments (3000 SWs dose) damaged &amp;lt;0.1% functional renal volume, suggesting minimal potential for adverse effects with low-pressure broad-focal-zone lithotripters. [NIH DK43881.]

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

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.

Critical Analysis of a New Generation Electrohydraulic Lithotripter: A Single Institution Experience with the Medispec E3000

The Medispec E3000(™) is a new generation electrohydraulic lithotripter with a wider focal width comparable to the Dornier HM3(™). We evaluate the efficacy of this machine for management of urinary stones at our institution by shockwave lithotripsy (SWL). There were 168 urinary calculi managed using the Medispec E3000 lithotripter over a 14-month period (10/2010-12/2011). During the first 6 months (10/2010-6/2011), a low power ramping protocol of 11-12-17 kV was used, and for the remaining 6 months (6/2011-12/2011), stones were managed with a higher power ramping protocol of 15-17-22.5 kV. A subanalysis of these groups was performed, as well as for stone location. The major end point was stone-free rate (SFR), defined as fragments <4 mm on follow-up imaging. Data were analyzed using the Fisher exact test and two-tailed Student t test. The study included 102 males and 66 females with an average age of 52.8 years. Mean stone size was 6.9 × 7.2 mm, which was significantly associated with SFR (P<0.0010). The overall SFR was 64.9%, with no significant difference between stones managed with the low power protocol (61.3%) and the high power protocol (70%). SFR varied by location across the upper pole (64.9%), midpolar area (57.1%), lower pole (68.4%), renal pelvis (79.2%), proximal ureter (66.6%), midureter (83.3%), and distal ureter (53.8%), but these differences were not significant (P=0.59). Efficiency quotient for the Medispec E3000™ was 54%. Overall, we achieved SFR of 64.9% in our initial experience with the Medispec E3000™. Optimizing treatment parameters may further improve success rates, and further outcomes follow-up may allow a more comprehensive evaluation of the lithotripter's overall efficacy.

Single-shot measurements of the acoustic field of an electrohydraulic lithotripter using a hydrophone array

Piezopolymer-based hydrophone arrays consisting of 20 elements were fabricated and tested for use in measuring the acoustic field from a shock-wave lithotripter. The arrays were fabricated from piezopolymer films and were mounted in a housing to allow submersion into water. The motivation was to use the array to determine how the shot-to-shot variability of the spark discharge in an electrohydraulic lithotripter affects the resulting focused acoustic field. It was found that the dominant effect of shot-to-shot variability was to laterally shift the location of the focus by up to 5 mm from the nominal acoustic axis of the lithotripter. The effect was more pronounced when the spark discharge was initiated with higher voltages. The lateral beamwidth of individual, instantaneous shock waves were observed to range from 1.5 mm to 24 mm. Due to the spatial variation of the acoustic field, the average of instantaneous beamwidths were observed to be 1 to 2 mm narrower than beamwidths determined from traditional single-point measurements that average the pressure measured at each location before computing beamwidth.

Evaluation of the LithoGold LG-380 Lithotripter:In VitroAcoustic Characterization and Assessment of Renal Injury in the Pig Model

Conduct a laboratory evaluation of a novel low-pressure, broad focal zone electrohydraulic lithotripter (TRT LG-380). Mapping of the acoustic field of the LG-380, along with a Dornier HM3, a Storz Modulith SLX, and a XiXin CS2012 (XX-ES) lithotripter was performed using a fiberoptic hydrophone. A pig model was used to assess renal response to 3000 shockwaves (SW) administered by a multistep power ramping protocol at 60 SW/min, and when animals were treated at the maximum power setting at 120 SW/min. Injury to the kidney was assessed by quantitation of lesion size and routine measures of renal function. SW amplitudes for the LG-380 ranged from (P(+)/P(-)) 7/-1.8 MPa at PL-1 to 21/-4 MPa at PL-11 while focal width measured ~20 mm, wider than the HM3 (8 mm), SLX (2.6 mm), or XX-ES (18 mm). For the LG-380, there was gradual narrowing of the focal width to ~10 mm after 5000 SWs, but this had negligible effect on breakage of model stones, because stones positioned at the periphery of the focal volume (10 mm off-axis) broke nearly as well as stones at the target point. Kidney injury measured less than 0.1% FRV (functional renal volume) for pigs treated using a gradual power ramping protocol at 60 SW/min and when SWs were delivered at maximum power at 120 SW/min. The LG-380 exhibits the acoustic characteristics of a low-pressure, wide focal zone lithotripter and has the broadest focal width of any lithotripter yet reported. Although there was a gradual narrowing of focal width as the electrode aged, the efficiency of stone breakage was not affected. Because injury to the kidney was minimal when treatment followed either the recommended slow SW-rate multistep ramping protocol or when all SWs were delivered at fast SW-rate using maximum power, this appears to be a relatively safe lithotripter.

An FDTD-based computer simulation platform for shock wave propagation in electrohydraulic lithotripsy

Extracorporeal Shock Wave Lithotripsy (ESWL) is based on disintegration of the kidney stone by delivering high-energy shock waves that are created outside the body and transmitted through the skin and body tissues. Nowadays high-energy shock waves are also used in orthopedic operations and investigated to be used in the treatment of myocardial infarction and cancer. Because of these new application areas novel lithotriptor designs are needed for different kinds of treatment strategies. In this study our aim was to develop a versatile computer simulation environment which would give the device designers working on various medical applications that use shock wave principle a substantial amount of flexibility while testing the effects of new parameters such as reflector size, material properties of the medium, water temperature, and different clinical scenarios. For this purpose, we created a finite-difference time-domain (FDTD)-based computational model in which most of the physical system parameters were defined as an input and/or as a variable in the simulations. We constructed a realistic computational model of a commercial electrohydraulic lithotriptor and optimized our simulation program using the results that were obtained by the manufacturer in an experimental setup. We, then, compared the simulation results with the results from an experimental setup in which oxygen level in water was varied. Finally, we studied the effects of changing the input parameters like ellipsoid size and material, temperature change in the wave propagation media, and shock wave source point misalignment. The simulation results were consistent with the experimental results and expected effects of variation in physical parameters of the system. The results of this study encourage further investigation and provide adequate evidence that the numerical modeling of a shock wave therapy system is feasible and can provide a practical means to test novel ideas in new device design procedures.

Preventing stone retropulsion during intracorporeal lithotripsy

Several studies of ureteroscopic treatment for ureteral stones have reported that most stone clearance failures can be attributed to stone fragment retropulsion. Stone retropulsion can result in increased operative time and cost-resulting from the need to change from the semi-rigid ureteroscope to a flexible instrument to chase migrated calculi-and additional procedures to treat residual migrated fragments are often required. The degree of migration depends mainly on the energy source used for lithotripsy; pneumatic and electrohydraulic lithotripters are associated with a greater degree of retropulsion than lasers. Different stone-trapping strategies and devices have been developed to minimize stone migration. Novel devices include the Lithovac(®) suction device, the Passport(™) balloon, the Stone Cone(™), the PercSys Accordion(®), the NTrap(®), and stone baskets such as the LithoCatch(™), the Parachute(™), and the Escape(®). Some authors have also reported on the use of lubricating jelly and BackStop(®) gel (a reverse thermosensitive polymeric plug); these devices are instilled proximal to the stone prior to the application of kinetic energy in order to prevent retrograde stone migration.

1842 SHOCKWAVE LITHOTRIPSY STONE-FREE RATES REMAIN POOR DESPITE DEVELOPMENT OF NEW GENERATION ELECTROHYDRAULIC LITHOTRIPTERS

You have accessJournal of UrologyStone Disease: New Technology/SWL, Ureteroscopic or Percutaneous Stone Removal III1 Apr 20121842 SHOCKWAVE LITHOTRIPSY STONE-FREE RATES REMAIN POOR DESPITE DEVELOPMENT OF NEW GENERATION ELECTROHYDRAULIC LITHOTRIPTERS Vincent Harisaran, Jessica Dai, Sammy Elsamra, Simone Thavaseelan, George Haleblian, and Gyan Pareek Vincent HarisaranVincent Harisaran Providence, RI More articles by this author , Jessica DaiJessica Dai Providence, RI More articles by this author , Sammy ElsamraSammy Elsamra Providence, RI More articles by this author , Simone ThavaseelanSimone Thavaseelan Providence, RI More articles by this author , George HaleblianGeorge Haleblian Providence, RI More articles by this author , and Gyan PareekGyan Pareek Providence, RI More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2012.02.1930AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Evidence supports that the newer generation lithotripters are not as effective as the original Dornier HM3™. Herein, we perform a critical analysis of 2 electrohydraulic lithotripters(LithoGold™ & Medispec™ E3000) utilized at our institution for the treament of urinary calculi. METHODS A total of 149 stones were treated over a 14-month period (2/2010 to 4/2011). Of these, 77 patients were treated by the LithoGold™ lithotripter (focal zone of 20 x 101 mm, penetration depth of 165mm) and 72 were treated with the Medispec E3000 (focal zone 13 x 60mm, penetration depth 135-170mm). Along with demographic data and stone characteristics, treatment outcomes were recorded for each patient. Specific endpoints included stone-free rates (SFR) defined by fragments less than 4mm on follow up imaging. Fisher's Exact test was used for analysis. RESULTS Outcomes were analyzed for 69 patients in the LithoGold group and 40 in the Medispec group. Average patient age was 53.5 (51 men, 18 women) and 55.3 (24 men, 16 women) years for the LithoGold and Medispec respectively. Average stone size was 6.7mm x 7mm and 6.6mm x 6.9mm in the LithoGold and Medispec groups respectively (P>0.05). Average shocks delivered per patient was 2660 (Lithogold) and 2453 (Medispec) (P>0.05). Stone location (LithoGold, Medispec) distribution was upper pole (7, 5), mid pole (8, 8), lower pole (20, 15), renal pelvis (20, 2), proximal ureter (9, 5), mid ureter (3, 1), and distal ureter (2,4). Overall SFR on follow-up imaging in the LithoGold group was 50%. By location, SFR revealed upper pole 71%, mid pole 86%, lower pole 20%, renal pelvis 40%, proximal ureter 33%, mid ureter 33%, and distal ureter 50%. In the Medispec group, overall SFR was 65%. By location, SFR revealed: upper pole 60%, mid pole 75%, lower pole 73%, renal pelvis 50%, proximal ureter 40%, mid ureter 100%, and distal ureter 50%. Overall SFR was NOT significant (p=0.065) between the 2 lithotripters, but there was a trend toward more overall success using the Medispec. CONCLUSIONS Despite theoretical technological advancement of newer generation electrohydraulic lithotripters, overall SFR remain poor. LithoGold™ demonstrated adequate SFR for upper and mid pole stones (71% and 86% respectively), but overall SFR were 50%. The Medispec™ demonstrated adequate SFR for lower pole stones (73%), with overall SFR of 65%. SFR for new generation lithotripters are overall poor and careful consideration for other endourological management is critical when counseling patients. © 2012 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 187Issue 4SApril 2012Page: e745 Advertisement Copyright & Permissions© 2012 by American Urological Association Education and Research, Inc.MetricsAuthor Information Vincent Harisaran Providence, RI More articles by this author Jessica Dai Providence, RI More articles by this author Sammy Elsamra Providence, RI More articles by this author Simone Thavaseelan Providence, RI More articles by this author George Haleblian Providence, RI More articles by this author Gyan Pareek Providence, RI More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Reduction of Bubble Cavitation by Modifying the Diffraction Wave from a Lithotripter Aperture

A new method was devised to suppress the bubble cavitation in the lithotripter focal zone to reduce the propensity of shockwave-induced renal injury. An edge extender was designed and fabricated to fit on the outside of the ellipsoidal reflector of an electrohydraulic lithotripter to disturb the generation of diffraction wave at the aperture, but with little effect on the acoustic field inside the reflector. Although the peak negative pressures at the lithotripter focus using the edge extender at 20 kV were similar to that of the original configuration (-11.1 ± 0.9 vs -10.6 ± 0.7 MPa), the duration of the tensile wave was shortened significantly (3.2 ± 0.54 vs 5.83 ± 0.56 μs, P<0.01). There is no difference, however, in both the amplitude and duration of the compressive shockwaves between these two configurations as well as the -6 dB beam width in the focal plane. The significant suppression effect of bubble cavitation was confirmed by the measured bubble collapse time using passive cavitation detection. At the lithotripter focus, while only about 30 shocks were needed to rupture a blood vessel phantom using the original HM-3 reflector at 20 kV, no damage could be produced after 300 shocks using the edge extender. Meanwhile, the original HM-3 lithotripter at 20 kV can achieve a stone comminution efficiency of 50.4 ± 2.0% on plaster-of-Paris stone phantom after 200 shocks, which is comparable to that of using the edge extender (46.8 ± 4.1%, P=0.005). Modifying the diffraction wave at the lithotripter aperture can suppress the shockwave-induced bubble cavitation with significant reduced damage potential on the vessel phantom but satisfactory stone comminution ability.