Electromagnetic Lithotripter Research Articles

Low‐frequency extracorporeal shock wave lithotripsy improves renal pelvic stone disintegration in a pig model

To compare disintegration rates for renal stones treated by 60 vs 120 shock waves (SW)/min at the same energy settings, using standardized validated artificial stones in a pig model. Gypsum artificial stones (13 x 6 mm) were inserted into the renal pelvis on either side of 12 anaesthetized pigs by open surgery. Extracorporeal SW lithotripsy (ESWL) was applied using a new electromagnetic lithotripter (Lithoskop, Siemens AG Healthcare, Munich, Germany) at 60 and 120 SW/min; 3000 SW were applied to each kidney with the same energy settings. Stone fragments were collected after nephrectomy, passed through calibrated test sieves, and weighed. Fragment size categories were stratified according to the sieve hole size as set by the manufacturer. Fragments of < or =4.75 mm were defined as capable of spontaneous passage. For each pig the number of stone fragments of the respective size categories was counted and weighed. The results were analysed statistically using the Mann-Whitney U-test. For fragments of >4.75 mm, the median (range) fragment counts were 0 (0-1) for 60 and 1 (0-3) for 120 SW/min (P = 0.006). For small fragments of 2.0-2.8 mm, the median fragment counts were 15 (4-24) for 60 and 10 (2-25) for 120 SW/min (P = 0.033); for fragments of 1.0-2.0 mm the respective values were 42.5 (9-81) and 21.5 (6-56) (P = 0.004). Of the total stone fragment mass in the 60 and 120 SW/min groups, 4.34% and 31.31% were >4.75 mm. There was complete disintegration yielding fragments capable of spontaneous passage in 10 of 12 renal units at 60 and in three of 12 renal units at 120 SW/min. The mean treatment time was 55.4 min for therapy at 60 and 34.3 min for therapy at 120 SW/min (P = 0.001). One parenchymal haematoma of 15 x 10 mm developed in the 60 SW/min group and another of 20 x 10 mm developed in the 120 SW/min group. ESWL fragmentation with equal energy application yields significantly smaller fragments at 60 than at 120 SW/min. The theoretical stone passage rate could therefore be approximately 80% for 60 vs 25% for 120 SW/min ESWL. Renal haematoma formation was comparable in both groups.

Improved impulse response for hydrophone measurements in therapeutic ultrasound fields.

The accurate measurement of pressure waveforms in high intensity focused ultrasound (HIFU) fields is complicated by the fact that many devices operate at output levels where shock waves can form in the focal region. In tissue ablation applications, the accurate measurement of the shock amplitude is important for predicting tissue heating since the absorption at the shock is proportional to the shock amplitude cubed. To accurately measure shocked pressure waveforms, not only must a hydrophone with a broad bandwidth (>100 MHz) be used, but the frequency response of the hydrophone must be known and used to correct the measured waveform. In this work, shocked pressure waveforms were measured using a fiber optic hydrophone and a frequency response for the hydrophone was determined by comparing measurements with numerical modeling using a KZK‐type equation. The impulse response was separately determined by comparing a measured and an idealized shock pulse generated by an electromagnetic lithotripter. The frequency responses determined by the two methods were in good agreement. Calculations of heating using measured HIFU waveforms that had been deconvolved with the determined frequency response agreed well with measurements in tissue phantom. [Work supported by NIH DK43881, NSBRI SMST01601, NIH EB007643, and RFBR.]

External shock waves therapy in dystonia: preliminary results

Extracorporeal shock wave therapy (ESWT) has been shown to reduce hypertonia in patients with upper motor neuron syndrome without any side effect. The aim of the present study is to investigate whether ESWT could be useful also in patients with dystonia. We evaluated three patients with secondary dystonia and three patients with idiopathic writer's cramp. Placebo treatment was performed in each patient. ESWT was administered during four sessions (once weekly) to the target muscles of hand and forearm using an electromagnetic lithotripter (Modulith SLK--Storz Medical). Clinical evaluation was performed using the Unified Dystonia Rating Scale in patients with secondary dystonia and the Arm Dystonia Disability Scale in patients with writer's cramp. After treatment, the three patients with secondary dystonia showed a marked improvement which lasted at least until 1 month after the last session. In the patients with writer's cramp, the improvement after ESWT was less consistent being effective only in two subjects. There were no associated adverse effects. Extracorporeal shock wave therapy is probably an effective and safe treatment for upper limb dystonia, particularly for the secondary forms. Larger randomized studies are needed to confirm these preliminary results.

Comparison of the effectiveness and safety of MPL 9000 and Lithostar Modularis shockwave lithotriptors: treatment results of 263 children

In this study, we aimed to compare the treatment results of two different shock wave lithotripsy (SWL) machines used in the management of pediatric urolithiasis. Between January 1993 and October 2004, Dornier MPL 9000 (electrohydraulic) had been used, and since then Siemens Lithostar Modularis (electromagnetic) has been used. The last evaluation was done 3 months after SWL treatment in terms of the success rate, use of anesthesia and complications. A total of 263 children (171 boys and 92 girls), with an age range of 9 months-14 years (mean age 8.1 +/- 3.8 years) were included in this study. Of the patients treated with the Dornier MPL 9000, 60.1% (173/104) required general anesthesia and 69 needed sedation. In contrast, for all patients treated with the Lithostar Modularis necessitated only sedo-analgesia (90 children). The hospital stay was shorter for Siemens Lithostar Modularis than those of Dornier MPL 9000 (26.2 vs. 35.5 h, P = 0.03). The success rate for the electromagnetic unit (86.5%) was almost identical that achieved with the electrohydraulic unit (85.2%) in the stones for the different location. Success rates were compared for stone burden subsets, the differences were insignificant for both lithotriptors (P > 0.05, for all). The electromagnetic unit had a significantly higher success rate for distal ureteral calculi (86.2 vs. 54.5%, P = 0.034). The efficiency quotients (EQ) for distal ureteral calculi were significantly different in favor of electromagnetic machine (56 vs. 40%). The complication rates for SWL were not significantly different for electrohydraulic and electromagnetic lithotriptors (8.7 and 6.2%, respectively). This study showed that SWL treatment was effective and safe in pediatric urolithiasis using both electrohydraulic and electromagnetic machines. Electromagnetic machine was more effective than electrohydraulic one for distal ureteral calculi. Additionally, the electromagnetic lithotriptor has significant clinical advantages over the electrohydraulic lithotriptor in terms of anesthesia requirements, hospitalization duration and fluoroscopic targeting.

Does the Type of Lithotripter Affect Outcomes in Children with Upper Tract Urolithiasis?

To compare the treatment outcome and short-term safety of electrohydraulic and electromagnetic lithotripters in children. Comparative analysis of children undergoing shockwave lithotripsy (SWL) with a Dornier MPL 9000 electrohydraulic lithotripter (EHL) and a Siemens Modularis electromagnetic lithotripter (EML) was performed. All SWL treatments were performed by a single operator under the supervision of an admitting urologist. The demographic features, stone, and treatment-related parameters, including complications, were analyzed for both groups. Stone-free (SF) rates, re-treatment rate, and efficiency quotient (EQ) were calculated and compared for the two groups. Ninety-eight children had SWL for renal and proximal ureteral stones. There were 58 children in the EHL group and 40 in the EML group. There were no statistically significant differences between the groups in terms of age, sex, type of anesthesia, diagnostic modality, site, side, and size of the stones. Number of shockwaves used with EML was greater than with EHL (P < 0.00). SF rate was 95% and 77% for EHL and EML, respectively, with a statistically significant difference (P < 0.00). The re-treatment rate was equal in either group. The complication rate was higher with the EHL compared with the EML, although it did not reach statistical significance. Steinstrasse was the most common complication noted. EQ was 66% for the EHL, in comparison with 53% for the EML. The EHL has a better SF and EQ than the EML; however, short-term safety is marginally better with the EML.

Extracorporeal shock wave lithotripsy in children: equivalent clearance rates to adults is achieved with fewer and lower energy shock waves

To compare the outcome, safety and efficiency of extracorporeal shock wave lithotripsy (ESWL) using an electromagnetic lithotripter for upper urinary tract stones in children and adults. We retrospectively reviewed data over a 5-year period for patients with solitary, renal and upper ureteric stones measuring <2 cm in whom ESWL was the treatment method. Group A consisted of 44 children (mean [SD] age 5.9 [4.4] years) and group B of 562 adults (mean [SD] age 40.9 [13.1] years). The number and energy of SWs used was not predetermined and was tailored until adequate fragmentation was achieved. Initial stone reassessment was performed at 48 h and monthly thereafter. The number of SWs, intensity of SWs, stone-free rate, auxiliary procedure rate, re-treatment rate, complication rate and effectiveness quotient (EQ) were assessed in each group. The stone-free rate with ESWL was 84% in children and 87% in adults (P = 0.78). The EQ was 77% and 75% in children and adults, respectively (P = 0.56). The mean (sd) number of SWs and energy required per session was 950 (349) and 11.83 (0.48) kV in children and 1262 (454) and 12.36 (0.34) kV in adults (P < 0.001). The re-treatment, auxiliary procedure and complication rates were similar in both groups. ESWL is as safe and effective in children as in adults for solitary renal and upper ureteric stones that are <2 cm. Children required significantly fewer and lower energy SWs to achieve equivalent results.

Efficacy and Treatment Outcome of a New Electromagnetic Lithotripter for Upper Urinary Tract Calculi

To evaluate the efficacy and treatment outcome of a new electromagnetic lithotripter-The Siemens Lithoskop-in the treatment of upper urinary tract stones. Data of 218 consecutively treated patients for upper urinary tract stones between August 2006 and December 2007 with complete follow-up was collected from a prospectively maintained data-base. All patients underwent outpatient based extracorporeal SWL with the shock wave system Pulso integrated into the Siemens Lithoskop platform. Mean surface areas of renal and ureteral stones were 65 +/- 59 mm(2) and 32 +/- 18 mm(2) respectively. Overall, 95% of urinary stones demonstrated fragmentation post SWL. After three months follow-up 84% and 88% of patients harboring renal and ureteral stones were regarded as treatment success. Patients harboring renal or ureteral stones <10 mm were successful treated in 95%. Auxiliary measures in renal and ureteral stones were necessary in 7.8 and 18.8% of patients respectively. Mean number of sessions performed for renal and ureteral stones were 1.6 +/- 1 and 1.4 +/- 0.8, respectively. No major complications as sepsis or renal hematoma were observed. Outpatient based electromagnetic SWL using the Lithoskop achieves high fragmentation and success rates with minimal analgesia requirements and a low complication rate.

Single Center, Single Operator Comparative Study of the Effectiveness of Electrohydraulic and Electromagnetic Lithotripters in the Management of 10- to 20-mm Single Upper Urinary Tract Calculi

This study compared the efficacy and safety profile of electrohydraulic (EH) and electromagnetic (EM) lithotriptors in the treatment of 10- to 20-mm renal and proximal ureteric stones at a single center and by a single operator. Between January 2001 and December 2006, we sequentially treated patients meeting study inclusion criteria with MPL 9000 Dornier EH for the first 3 years, followed by the EM Siemens Modularis shockwave lithotripsy (SWL) unit. A single operator performed all SWL treatments under the supervision of an admitting urologist. We analyzed the demographic features and stone- and treatment-related parameters including complications for both groups. In each group, the stone-free rate and efficiency quotient was determined at 1-3 months. Of 274 patients, we sequentially treated 112 using the EH lithotriptor, and 162 the EM lithotriptor. The pre-SWL patients and stone-related parameters were similar in the two groups, except for diagnostic imaging modalities. The mean number of SWL sessions, need for ancillary procedure, retreatment rate, stone location, stone-free rate, and efficiency quotient were not significantly different between groups. The mean number of shockwaves required for complete fragmentation was 2977 and 6044 (P < .000) for the EH and EM groups, respectively. Single center, single operator experience with two types of lithotriptor indicated that both are equally efficacious, with similar safety profiles. The only significant difference was that the EH lithotriptor required fewer shockwaves for fragmentation.

Editorial Comment

Any urologist would like an opportunity to improve stone free rates when using SWL, particularly when there is no significantly added cost or morbidity. These authors correlated SF outcomes from 200 patients undergoing SWL using an electromagnetic lithotripter with Hounsfield unit density (HUD), skin-to-stone distance (SSD), and body mass index (BMI). They also assessed the old standards, stone size, and intrarenal location. SF status was measured once at 6 weeks, with the use of only plain abdominal films.

Prospective evaluation of acute endocrine pancreatic injury as collateral damage of shock‐wave lithotripsy for upper urinary tract stones

There has been controversy over whether extracorporeal shock wave lithotripsy (ESWL) can cause damage to the endocrine cells of the pancreas, leading to the later development of diabetes mellitus. Authors from Germany prospectively evaluated acute endocrine pancreatic injury as collateral damage caused by the ESWL for treating upper urinary tract stones. In a careful study they showed that there was no effect on serum levels of variables indicating exocrine and endocrine pancreatic tissue damage, suggesting that the idea that ESWL might lead to future diabetes mellitus is unlikely to be correct. To detect acute damage to pancreatic cells by extracorporeal shock wave lithotripsy (ESWL), with a focus on endocrine function, as recently the development of diabetes mellitus has been suggested to be a late complication of treatment of upper urinary tract stones, and injury to pancreatic tissue by ESWL, leading to insufficient endocrine function, has been proposed as an explanation of this effect. The study included 12 consecutive patients treated with ESWL for proximal ureteric or kidney stones, using a third-generation electromagnetic lithotripter. To evaluate pancreatic tissue injury caused by ESWL we determined blood variables known to indicate exocrine and endocrine pancreatic cell damage; blood samples were taken before, during, immediately after, and 1 h and 24 h after ESWL to determine the serum levels of amylase, lipase, insulin, glucose, c-peptide and glucagon. Eight patients treated with ESWL for distal ureteric stones were evaluated in the same way and served as the control group. Neither the variables indicating islet cell damage (c-peptide, insulin and glucagon), nor those indicating damage of exocrine pancreatic cells (amylase and lipase) changed significantly over the time course in both groups. We could detect no immediate effect on the serum levels of variables indicating exocrine or endocrine pancreatic tissue damage caused by ESWL for urinary tract stones. The hypothesis that ESWL leads to pancreatic trauma with consecutive development of diabetes mellitus therefore seems unlikely.

Independent assessment of a wide‐focus, low‐pressure electromagnetic lithotripter: absence of renal bioeffects in the pig

To assess the renal injury response in a pig model treated with a clinical dose of shock waves (SWs) delivered at a slow rate (27 SW/min) using a novel wide focal zone (18 mm), low acoustic pressure (<20 MPa) electromagnetic lithotripter (Xi Xin-Eisenmenger, XX-ES; Xi Xin Medical Instruments Co. Ltd., Suzhou, PRC). The left kidneys of anaesthetized female pigs were treated with 1500 SWs from either an unmodified electrohydraulic lithotripter (HM3, Dornier MedTech America, Inc., Kennesaw, GA, USA; 18 kV, 30 SW/min) or the XX-ES (9.3 kV, 27 SW/min). Measures of renal function (glomerular filtration rate, GFR, and renal plasma flow) were collected before and after SW lithotripsy, and kidneys were harvested for histological quantification of vascular haemorrhage, expressed as a percentage of the functional renal volume (FRV). A fibre-optic probe hydrophone was used to characterize the acoustic field, and the breakage of gypsum model stones was used to compare the function of the two lithotripters. Kidneys treated with the XX-ES showed no significant change in renal haemodynamic function and no detectable tissue injury. Pigs treated with the HM3 had a modest decline from baseline ( approximately 20%) in both GFR (P > 0.05) and renal plasma flow (P = 0.064) in the treated kidney, but that was not significantly different from the control group. Although most HM3-treated pigs showed no evidence of renal tissue injury, two had focal injury measuring 0.1% FRV, localized to the renal papillae. The width of the focal zone for the XX-ES was approximately 18 mm and that of the HM3 approximately 8 mm. Peak positive pressures at settings used to treat pigs and break model stones were considerably lower for the XX-ES (17 MPa at 9.3 kV) than for the HM3 (37 MPa at 18 kV). The XX-ES required fewer SWs to break stones to completion than did the HM3, with a mean (sd) of 634 (42) and 831 (43) SWs, respectively (P < 0.01). However, conditions were different for these tests because of differences in physical configuration of the two machines. The absence of renal injury with the wide focal zone XX-ES lithotripter operated at low shock pressure and a slow SW rate suggests that this lithotripter would be safe when used at the settings recommended for patient treatment. That the injury was also minimal using the Dornier HM3 lithotripter at a slow SW rate implies that the reduced tissue injury seen with these two machines was because they were operated at a slow SW rate. As recent studies have shown stone breakage to be improved when the focal zone is wider than the stone, a wide focal zone lithotripter operated at low pressure and slow rate has the features necessary to provide better stone breakage with less tissue injury.

POS-01.104: ESWL for treatment of large ureteral stones

Dornier Compact Delta is an electromagnetic lithotripter designed with modules. It is cost-efficient. The localization of calculi with XR imaging is assisted with HOFMANN FS 2000 X-ray targeting system. Optimal treatment of large stones in ureter is still controversial. The aim of our study was to determine the efficacy and safety of ESWL in patients with ureteral stones larger than 10 mm.

A Prospective Multivariate Analysis of Factors Predicting Stone Disintegration by Extracorporeal Shock Wave Lithotripsy: The Value of High-Resolution Noncontrast Computed Tomography

ObjectiveTo assess the value of noncontrast computed tomography (NCCT) as a possible predictor of renal stone disintegration by shock wave lithotripsy (SWL). Patients and methodsThe study included 120 consecutive patients (71 males, 49 females; mean age: 42.6 yr) with a solitary renal stone of 0.5–2.5cm in length. NCCT was performed using a multidetector row CT scanner at 120KV and 240mA, with 1.25-mm collimation. A bone window was used to measure stone attenuation values. SWL was performed with an electromagnetic lithotripter. Failure of disintegration was defined as no fragmentation of the stone after three sessions. The impact of patients’ sex, age, and body mass index (BMI) and the stones’ laterality, location, volume, mean attenuation value, and the skin-to-stone distance on disintegration were evaluated by univariate and multivariate analyses. ResultsFailure of disintegration was observed in 15 patients (12.5%). BMI and stone density >1000HU were the significant independent predictors of failure (p=0.04 and 0.02, respectively). The success rate of extracorporeal SWL at 3 mo was 87.5% (105 of 120 patients); 90 patients were stone free and 15 had residual fragments <4mm. The only significant predictor of residual fragments was stone density (p<0.001). ConclusionsObesity and increased stone density as detected by NCCT are significant predictors of failure to fragment renal stones by SWL. An alternative treatment should be devised for obese patients with stone density >1000HU.

Air Pockets Trapped During Routine Coupling in Dry Head Lithotripsy Can Significantly Decrease the Delivery of Shock Wave Energy

Current lithotriptors use a dry treatment head that must be coupled to the patient with gel or oil. We determined how the quality of coupling affects stone breakage under conditions that simulated patient treatment. Experiments were performed with a Dornier (DoLi-50 electromagnetic lithotriptor. The test tank had a clear Mylar membrane for coupling with the treatment head water cushion. Thus, air pockets trapped at the coupling interface could be photographed for quantitation. Coupling efficiency was assessed using a fiberoptic hydrophone and different coupling regimes were tested for the effect on gypsum stone breakage. The quality of coupling was variable with air pockets covering 1.5% to 19% of the coupling area, resulting in a mean decrease in shock wave amplitude of approximately 20%. Breaking and reestablishing contact, as when a patient is repositioned during treatment, decreased acoustic pressure almost 32%, representing a 57% decrease in acoustic energy transmission. Stone breakage was also decreased when air was trapped in coupling and only 2% coverage by air pockets decreased stone breakage by 20% to 40%. These in vitro results suggest that coupling in lithotripsy can pose a significant barrier to the transmission of shock wave energy to the patient. Stone breakage was sensitive to air pockets at the coupling interface. Recoupling was particularly disruptive, suggesting that repositioning the patient could substantially degrade coupling quality. It seems reasonable that variability in the quality of coupling could contribute to variability in clinical outcomes.

A sensitive, broadband polyvinylidine difluoride (PVDF) hydrophone for accurate characterization of shock waves

Few hydrophones are capable of measuring high‐intensity fields such as shock waves accurately. One of the more reliable is the fiber‐optic probe hydrophone. However, this system is expensive and insensitive. We created a new PVDF hydrophone and compared it with a fiber‐optic system. The hydrophone consisted of a 25‐μm‐thick PVDF membrane with a 0.5‐mm active element and a preamplifier, which were each held in separate attached polycarbonate housings. The amplifier had adjustable gain and could account for membrane resonance to flatten the frequency response. A model of the frequency response for the system was developed, which agreed well with the measured response. Shock waves were measured in two Dornier HM‐3 clones and an electromagnetic lithotripter. Measurements were also recorded using a 2‐MHz focused piezoceramic source and a broadband PVDF source. Shock‐wave measurements closely matched those recorded by the fiber‐optic hydrophone and calculations made with a KZK‐type model. Very little damage to the membrane was found after applying several thousand shock waves. This new membrane hydrophone is robust and sufficiently accurate to measure high‐intensity fields, while greatly reducing cost, increasing sensitivity, and simplifying measurements of shock waves. [Work supported by NIH DK43881, DK55674, and NSBRI SMS00402.]

Detection of Significant Variation in Acoustic Output of an Electromagnetic Lithotriptor

We describe the observation of significant instability in the output of an electromagnetic lithotriptor. This instability had a form that was not detected by routine assessment, but rather was observed only by collecting many consecutive shock waves in nonstop regimen. A Dornier DoLi-50 lithotriptor used exclusively for basic research was tested and approved by the regional technician. This assessment included hydrophone measures at select power levels with the collection of about 25 shock waves per setting. Subsequent laboratory characterization used a fiberoptic hydrophone and storage oscilloscope for data acquisition. Waveforms were collected nonstop for hundreds of pulses. Output was typically stable for greater than 1,000 shock waves but substantial fluctuations in acoustic pressures were also observed. For example, output at power level 3 (mean peak positive acoustic pressure +/- SD normally 44 +/- 2 MPa) increased dramatically to greater than 50 MPa or decreased significantly to approximately 30 MPa for hundreds of shock waves. The cause of instability was eventually traced to a faulty lithotriptor power supply. Instability in lithotriptor acoustic output can occur and it may not be detected by routine assessment. Collecting waveforms in a nonstop regimen dramatically increases sampling size, improving the detection of instability. Had the instability that we observed occurred during patient treatment, the energy delivered may well have exceeded the planned dose. Since the potential for adverse effects in lithotripsy increases as the dose is increased, it would be valuable to develop ways to better monitor the acoustic output of lithotriptors.

Single-Center Experience Using Three Shockwave Lithotripters with Different Generator Designs in Management of Urinary Calculi

We retrospectively reviewed the treatment outcomes of extracorporeal shockwave lithotripsy (SWL) in a single center using either the Wolf Piezolith 2300 (a piezoelectric lithotripter), the Dornier MPL9000 (an electrohydraulic lithotripter), or the Dornier Compact Delta (an electromagnetic lithotripter) from January 1992 to June 2002. A series of 3123 (1449 Piezolith 2300, 780 MPL9000, and 894 Compact Delta) solitary radiopaque urinary stones of < or =15 mm receiving primary SWL were identified. "Stone free" was defined as the absence of evidence of stone on plain radiography. Treatment outcomes were assessed by the stone-free rate 3 months after one treatment session, the retreatment rate, the auxiliary procedure rate, the complication rate, and the effectiveness quotient (EQ). In order to have a better assessment of the efficacy of individual lithotripters, multiple logistic regression was performed to control various factors affecting treatment outcomes, including lithotripter-type, patients' sex and age, history of previous SWL, the stone characteristics (side, site, and size), and the presence of a stent or nephrostomy tube. There were significant differences in the stone site distribution and mean stone size among the three groups. The overall EQ for the Piezolith 2300, MPL9000, and Compact Delta were 0.345, 0.303, and 0.257, respectively. However, using the multiple logistic regression model, the adjusted odds ratio (AOR) of a patient being stone-free after 3 month for the Piezolith 2300 and MPL9000 (using the Compact Delta as the referent category) were 1.38 (95% CI 1.15, 1.65) and 1.72 (95% CI 1.39, 2.11), respectively. Patients treated using the MPL9000 had significantly less re-treatment (AOR = 0.57; 95% CI 0.48, 0.69) than the other groups. No significant difference in the auxiliary procedure rate and complication rate for the three machines was observed. Based on multivariate analysis results, the Dornier MPL9000 had the best treatment outcomes in terms of stone-free rate and re-treatment rate among the three lithotripters.

Shock Wave Lithotripsy for Uric Acid Stones

To report our experience of extracorporeal shock wave lithotripsy (SWL) for patients with uric acid stones. From December 1987 to December 2003, a total of 443 patients with uric acid stones in the kidney or ureter accepted SWL using ultrasound-guided lithotripters together with alkali therapy. Among them, 168 patients with an average stone burden of 9.1 mm were treated using an EDAP LT-01 piezoelectric lithotripter. The other patients, with an average stone burden of 9.6 mm, were treated using a Dornier Compact S electromagnetic lithotripter. The average duration of treatment using the EDAP LT-01 device was 52.1 minutes with a pulse frequency of 1.25-2.5 shocks per second at 100% power. The average treatment parameters on the Dornier Compact S device were 3,196 shocks at 14.8 kV. For the EDAP LT-01, the 3-month stone-free rate was 86.4%, with a retreatment rate of 24.2%. For the Dornier Compact S, the 3-month stone-free rate was 90.3%, with a retreatment rate of 29.0%. Auxiliary therapy with the push-back technique was needed in 0.45% of patients with upper ureteral stones that could not be localized using ultrasound. The treatment results were best for stones smaller than 20 mm. No anaesthesia was required for any patient. SWL with ultrasound localization for uric acid stones is safe and effective. The combination of SWL with urine alkalization may further improve the stone-free rate.

Shockwave Lithotripsy: Instrumentation and Status in China

To introduce the physical background and technical characteristics of lithotripters made in China and to compare the efficacy of shockwave lithotripsy (SWL) for distal-ureteral stones between Chinese and Western lithotripters in consecutive use in our stone center. From December 1987 to December 2003, we used a series of four lithotripters to treat 1802 patients with distal-ureteral stones: the piezoelectric EDAP LT-01 with ultrasound B-mode scanning for localization (N = 179); the electrohydraulic JDPN-IV lithotripter using fluoroscopy, which is made in China (N = 294), the electromagnetic Dornier Compact S with fluoroscopy/ultrasound dual localization (N = 1105), and the Huikang MZ-SWL-V, which is an electromagnetic- and electrohydraulic-compatible machine with dual localization that is made in China (N = 224). The physical background and technical characteristics of Chinese lithotripters are different from those of Western machines, but the treatment strategies were identical in all series. In the EDAP LT-01 series, the retreatment rate was 35.2%, and the auxiliary procedure rate was 6.7%, bring the efficiency quotient (EQ) to 69%. In the JDPN-IV series, the retreatment rate was 27.6%, the auxiliary procedure rate 1.0%, and the EQ 74%. In the Dornier Compact S series, the retreatment rate was 12.9%, and auxiliary procedures were performed in 10.9%, for an EQ of 81%. In the Huikang MZ-SWL-V series, the retreatment rate was 20.1%, the auxiliary procedure rate was 4.9%, and the EQ was 80%. The fragmentation results of Chinese electrohydraulic and electromagnetic lithotripters are superior to those of the EDAP LT-01. Chinese lithotripters are inferior to the Dornier Compact S in the efficacy of stone fragmentation, but Chinese machines cause less pain than this lithotripter.

Low-frequency ultrasonic piezoceramic sandwich transducer

This paper presents an ultrasonic piezoceramic sandwich transducer (UPST), utilised for ultrasonic field generation in water and cavitational effect achievement. This device will be used to produce enlargement of the bubbles, initiated by the incident shock wave on the calculus in the lithotripsy process. The piezoceramic sandwich transducer powered by a function/pulse generator type IWATSU SG-4511 converts the electrical signal in mechanical vibrations, which are propagated in water. A PZT disc sensor converts the underwater waves in electrical signals, displayed by LeCroy 9310 AM oscilloscope. The purpose was to realise an ultrasonic piezoceramic sandwich transducer with low resonance frequency, tuneable energy and broad bandwidth. The UPST transducer, integrated to an ESWL electromagnetic lithotripter, yields enhancement of the cavitation effects, utilised in the comminution of kidney stones.