Electromagnetic Shock Wave Lithotripter Research Articles

Treatment of Moderate-sized Kidney Stone with Third-generation Electromagnetic Shock Wave Lithotripter

BACKGROUND: The extracorporeal shock wave lithotripsy (ESWL) is a non-invasive method in the treatment of urinary tract stones and its discovery has led to a complete change in the therapeutic strategy for urolithiasis. Due to the low morbidity and excellent fragmentation of the stones, ESWL has proven to be an effective and non-invasive method in the treatment of renal stones.
 AIM: The aim of this retrospective study is to evaluate the efficacy and safety of the ESWL as a monotherapy in the treatment of moderate size kidney stones with stone area (SA) of 100–300 mm².
 MATERIALS AND METHODS: We made a retrospective study of 98 patients with moderate size kidney stones with SA of 100–300 mm², divided into two subgroups, into a group with a SA of 100–200 mm² and with 200–300 mm², treated with ESWL in the period of November 2018–December 2019. The patients were treated with a third-generation electromagnetic lithotripter (Lithoskop®, Siemens Medical Systems, Erlangen, Germany), with a source of electromagnetic shocks (Pulso™) and dual ultrasonographic/fluoroscopic system for detection of the stones. The stone location, size, maximum energy used, localization technique, number of shock waves, sessions, re-treatment rate, and additional procedures were reviewed. All the patients before the intervention had a complete laboratory and radiological examinations. Postoperatively, patients were monitored on the 1st, 30th, and 90th post-operative days.
 RESULTS: Ninety-eight patients with solitary kidney stone with a SA of 100–300 mm² were treated with ESWL. The study included 58 men (59.18%) and 44 women (40.81%). The average length and width of the stone were 15.47 ± 2.68 mm and 12.99 ± 2.83 mm, respectively. The average surface area of the stones in our series was 203.78 ± 72.85 mm². The mean number of treatments for the entire series of patients was 1.82 ± 0.91. The mean number of shock waves for the total series of patients was 3899.11 ± 40. The mean energy used for the overall patient series was 110106.17 ± 21489.61 mJ. The total re-treatment rate was 47.95%. The entire rate of additional procedures was 19.38%. The overall success rate (SR) in our study was 77.55%. The efficiency quotient for the upper-middle and lower calyx was 55.57, 57.15, and 30.81, respectively.
 CONCLUSION: ESWL is a safe and effective method in the treatment of renal stones, and we recommend as the first method in the treatment of moderate size kidney stone with a surface area of 100–300 mm². The treatment of each patient should be individualized and take into account all favored and non-favored factors that influence the decision to choose extracorporeal lithotripsy as a method of treatment of medium-sized stones.

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

The effects of stone size on the process and comminution efficiency of shock wave lithotripsy (SWL) were investigated in experiments, numerical simulations and scale analysis. Cylindrical BegoStone phantoms with approximately equal height and diameter of either 4, 7 or 10 mm, in a total aggregated mass of about 1.5 g, were treated in an electromagnetic shock wave lithotripter field. The resultant stone comminution was found to correlate closely with the average peak pressure, P+(avg), incident on the stones. The P+(avg) threshold necessary to initiate stone fragmentation in water increased from 7.9 to 8.8 to 12.7 MPa, respectively, as stone size decreased from 10 to 7 to 4 mm. Similar changes in the P+(avg) threshold were observed for the 7- and 10-mm stones treated in 1,3-butanediol, in which cavitation is suppressed, suggesting that the observed size dependency is due to changes in stress distribution within stones of different size. Moreover, the slope of the correlation curve between stone comminution and ln(P¯+(avg)) in water increased with decreasing stone size, whereas the opposite trend was observed in 1,3-butanediol. The progression of stone comminution in SWL exhibited size-dependence: the 7- and 10-mm stones fragmented into progressively smaller pieces, whereas a significant portion (>30%) of the 4-mm stones reached a stalemate within the size range of 2.8 ∼ 4 mm, even after 1000 shocks. Analytical scaling considerations suggest size-dependent fragmentation behavior, a hypothesis further supported by numerical model calculations that reveal changing patterns of constructive and destructive wave interference and, thus, variations in the maximum tensile stress or stress integral produced in cylindrical and spherical stone of different sizes.

Improving the lens design and performance of a contemporary electromagnetic shock wave lithotripter

The efficiency of shock wave lithotripsy (SWL), a noninvasive first-line therapy for millions of nephrolithiasis patients, has not improved substantially in the past two decades, especially in regard to stone clearance. Here, we report a new acoustic lens design for a contemporary electromagnetic (EM) shock wave lithotripter, based on recently acquired knowledge of the key lithotripter field characteristics that correlate with efficient and safe SWL. The new lens design addresses concomitantly three fundamental drawbacks in EM lithotripters, namely, narrow focal width, nonidealized pulse profile, and significant misalignment in acoustic focus and cavitation activities with the target stone at high output settings. Key design features and performance of the new lens were evaluated using model calculations and experimental measurements against the original lens under comparable acoustic pulse energy (E+) of 40 mJ. The -6-dB focal width of the new lens was enhanced from 7.4 to 11 mm at this energy level, and peak pressure (41 MPa) and maximum cavitation activity were both realigned to be within 5 mm of the lithotripter focus. Stone comminution produced by the new lens was either statistically improved or similar to that of the original lens under various in vitro test conditions and was significantly improved in vivo in a swine model (89% vs. 54%, P = 0.01), and tissue injury was minimal using a clinical treatment protocol. The general principle and associated techniques described in this work can be applied to design improvement of all EM lithotripters.

Success of electromagnetic shock wave lithotripter as monotherapy in large renal calculi—Our experience

ObjectivesTo evaluate the success of shock wave lithotripsy (SWL) as monotherapy for solitary renal stones larger than 2cm without ureteral stenting. Hence, if our study result demonstrates acceptable success and safety, we can recommend ESWL as a treatment option for patients with large renal calculi. Subjects and methodsThis is a prospective study conducted in the Department of Urology, Regional Institute of Medical Sciences, Imphal, India, from January 2011 to December 2012. A total of 104 patients aged between 20 and 70 years with solitary large (>2cm) renal stones underwent ESWL using the Dornier Compact Sigma Lithotripter. Stone size was calculated by measuring the largest dimension of the stone in KUB plain films. In each session, 3000–3500 shocks at frequency 60–90min−1 and intensity between 1 and 4 were given. A maximum number of six sessions were given. Successful treatment was defined as complete clearance or residual stones smaller than 4mm on KUB performed 3 months after the first session. ResultsTotal number of patients was 104. The M:F ratio was 1:1.4. The stone size ranged from 21 to 55mm. The overall success rate was 73%. For stones >30mm, the success rate was only 62.2% (n=28). The number of sessions required increased as the stone size increased. The most common complication encountered was haematuria. ConclusionESWL remains the cornerstone of therapy for renal calculi less than 2cm. Our study reveals that multiple sessions were required for solitary renal calculi, with higher rate of ancillary procedures. The success rate of ESWL for both non-staghorn and staghorn calculi with size above 2cm is low, so other treatment modalities like PCNL should be considered as the first treatment option. However, with appropriate patient selection, significant improvements in stone-free rates may be achieved.

Treatment efficacy and outcomes using a third generation shockwave lithotripter

To evaluate the clinical efficiency of a third generation electromagnetic shock wave lithotripter, the Lithoskop(®) (Siemens, Erlangen, Germany), regarding outcomes, stone disintegration, retreatment and complication rates. To compare the results of the Lithoskop with other currently available systems and the reference standard lithotripter, the HM-3 (Dornier MedTech Europe GmbH, Wessling, Germany). We analysed the data from 183 patients, including 13 children, undergoing extracorporeal shock wave lithotripsy (ESWL) for renal and ureteric calculi collected from a prospectively populated database. Outcomes were assessed by plain abdominal film of kidney, ureter and bladder and renal ultrasonography for radiopaque and computerized tomography for radiolucent stones 1 day after treatment and after 3 months. We analysed stone size and location before and after treatment, stone disintegration rate, retreatment rate, stone-free and residual fragment rates after 3 months, along with auxiliary procedures and complications. The mean (range) patient age was 48.6 (1.3-81.4) years, including 13 children with a mean (range) age of 8.4 (1.3-16.7) years, and 77% of the patients were male. In all, 46% of the calculi were localized in the kidney and 54% in the ureter. Renal stones were localized in the upper, middle and lower calyx and in the renal pelvis in 9, 29, 30 and 32% of patients, respectively. Ureteric stones were localized in the upper, mid- and distal ureter in 29, 19 and 52% of patients, respectively. The median (range) stone size before ESWL was 10 (4-25) mm in the kidney and 8 (4-28) mm in the ureteric calculi. The overall stone-free rate after 3 months was 91% (88% for renal and 93% for ureteric calculi); the mean number of sessions to achieve these rates was 1.3. Stone-free rates and the required number of sessions were determined only by stone size. In 7.1% of the patients (n = 13) post-interventional auxiliary procedures were necessary. We observed one perirenal haematoma as a major complication (0.5%), but this did not require any further therapy. Clinical stone-free rates with the Lithoskop are high and similar to those of other available systems, including the reference standard HM-3 lithotripter. Retreatment and complication rates are low, supporting the use of ESWL as first-line therapy for urinary calculi <10 mm, independent of stone location.

Assessment of a Modified Acoustic Lens for Electromagnetic Shock Wave Lithotripters in a Swine Model

The acoustic lens of the Modularis electromagnetic shock wave lithotripter (Siemens, Malvern, Pennsylvania) was modified to produce a pressure waveform and focal zone more closely resembling that of the original HM3 device (Dornier Medtech, Wessling, Germany). We assessed the newly designed acoustic lens in vivo in an animal model. Stone fragmentation and tissue injury produced by the original and modified lenses of the Modularis lithotripter were evaluated in a swine model under equivalent acoustic pulse energy (about 45 mJ) at 1 Hz pulse repetition frequency. Stone fragmentation was determined by the weight percent of stone fragments less than 2 mm. To assess tissue injury, shock wave treated kidneys were perfused, dehydrated, cast in paraffin wax and sectioned. Digital images were captured every 120 μm and processed to determine functional renal volume damage. After 500 shocks, the mean ± SD stone fragmentation efficiency produced by the original and modified lenses was 48% ± 12% and 52% ± 17%, respectively (p = 0.60). However, after 2,000 shocks, the modified lens showed significantly improved stone fragmentation compared to the original lens (mean 86% ± 10% vs 72% ± 12%, p = 0.02). Tissue injury caused by the original and modified lenses was minimal at a mean of 0.57% ± 0.44% and 0.25% ± 0.25%, respectively (p = 0.27). With lens modification the Modularis lithotripter demonstrates significantly improved stone fragmentation with minimal tissue injury at a clinically relevant acoustic pulse energy. This new lens design could potentially be retrofitted to existing lithotripters, improving the effectiveness of electromagnetic lithotripters.

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

To investigate the roles of lithotripter shock wave (LSW) parameters and cavitation in stone comminution, a series of in vitro fragmentation experiments have been conducted in water and 1,3-butanediol (a cavitation-suppressive fluid) at a variety of acoustic field positions of an electromagnetic shock wave lithotripter. Using field mapping data and integrated parameters averaged over a circular stone holder area (Rh=7mm), close logarithmic correlations between the average peak pressure (P+(avg)) incident on the stone (D=10mm BegoStone) and comminution efficiency after 500 and 1000 shocks have been identified. Moreover, the correlations have demonstrated distinctive thresholds in P+(avg) (5.3MPa and 7.6MPa for soft and hard stones, respectively), that are required to initiate stone fragmentation independent of surrounding fluid medium and LSW dose. These observations, should they be confirmed using other shock wave lithotripters, may provide an important field parameter (i.e., P+(avg)) to guide appropriate application of SWL in clinics, and facilitate device comparison and design improvements in future lithotripters.

Comparison of Efficacy of German and Chinese Electromagnetic Shock Wave Lithotripters: Dornier Compact S vs Huikang MZ-SWL-V

To compare the treatment efficacy of Dornier Compact S and a Chinese electromagnetic shock wave lithotripter (Huikang MZ-SWL-V) in a large series. We retrospectively reviewed the outcome of shock wave lithotripsy (SWL) in 13,954 consecutive patients with upper urinary tract stones from December 1996 to December 2008 with Dornier Compact S (9124 cases) and Huikang MZ-SWL-V (4830 cases). An intramuscular injection of 50 mg pethidine was given to the patients with Dornier Compact S but not to those with Huikang MZ-SWL-V. Treatment outcomes were assessed by the stone-free rate at three months, the retreatment rate, the auxiliary procedure rate, and the effectiveness quotient. The pain scores were evaluated by visual analog scales, where 0 = pain and 10 = unbearable pain. The overall stone-free rate at 3 months, retreatment rate, and ancillary procedure rate for Dornier Compact S were 95.9%, 13.4%, and 2.2%, respectively, and they were 85%, 29.6%, and 10.2%, respectively, for Huikang MZ-SWL-V. The overall efficiency quotients of Dornier Compact S and Huikang MZ-SWL-V were 83% and 60.8%, respectively. However, the pain scores in the Dornier group (6-10) were higher than those in the Huikang group (1-5). Three clinically significant subcapsular hematomas were detected in the Dornier group but there were none in the Huikang group. Dornier Compact S is more effective than Huikang MZ-SWL-V, but SWL with Huikang machine could be performed with milder pain and without analgesia, and a lower significant hematoma rate was observed in Huikang group.

Comparison of efficacy between emergency ESWL and elective ESWL in management of ureteral stones

Objective To compare the efficacy of the emergency ESWL within 24 hours after the onset of renal colic and elective ESWL at 5 - 7 days after the onset of renal colic in the treatment for ureteral stones.Method From January 2008 to October 2009, 365 patients in the Second Hospital of Nanchang, with ureteral stones were admitted to our department for renal colic. They underwent emergency ESWL or elective ESWL with HK. ESWL- 108 energy electromagnetic shock wave lithotripter. Success rate of fragmentation, stone-free rate after 2 weeks of operation, pain recurrence rate, and complications were evaluated. The data were analyzed using SPSS 15.0. Results The success rate of fragmentation and the stone-free rate after 2 weeks of emergency ESWL were 96.76% and96.21%, respectively, which were higher than those (88.33% and 87.22%, respectively) of elective ESWL ( P ＜ 0. 05). The postoperative pain recurrence rate of emergency ESWL ( 4.32 % ) was lower than that (9.44%) of elective ESWL ( P ＜0.05). There was no difference of total complications between emergency ESWL (3.24%) and elective ESWL (2.78%) group (P ＞0.05). Conclusions Emergency ESWL is superior to selective ESWL and is the safe and effective method for the management of ureteral stones. Key words: Emergency; Elective; Extracorporeal shock wave lithotripsy; Ureteral stones; Effect

Extracorporeal Shock Wave Lithotripsy for Prevention of Recurrent Pancreatitis Caused by Obstructive Pancreatic Stones

Obstructive pancreatic duct stones can cause recurrent attacks of acute pancreatitis and chronic abdominal pain. Use of extracorporeal shock wave lithotripsy (ESWL) for treatment of abdominal pain associated with obstructive pancreatic duct stones has been well documented. However, its effect on prevention of recurrent pancreatitis in this group of patients has not been studied. Patients with recurrent episodes of acute pancreatitis due to obstructive pancreatic duct stones not amenable to endoscopic removal were prospectively examined. All patients underwent ESWL by a pancreatologist using an electromagnetic shock wave lithotripter. After ESWL, the patients were followed up for recurrence of acute pancreatitis. Ten patients underwent 13 sessions of ESWL. Complete and partial ductal clearances were achieved in 7 and 3 patients, respectively. The mean length of follow-up was 20 months (range, 12-36 months). Three patients had recurrent attacks of acute pancreatitis during the follow-up period, caused by recurrence of obstructive stones in 2 and presence of main duct stricture in 1 patient. Extracorporeal shock wave lithotripsy of obstructive pancreatic duct stones in patients with recurrent attacks of acute pancreatitis can prevent further attacks. New episodes of acute pancreatitis in this group of patients may indicate stone recurrence or presence of strictures. CT - computed tomography, ERCP - endoscopic retrograde cholangiopancreatography, ESWL - extracorporeal shock wave lithotripsy.

Clinical Experience with Ultrasound-Based Real-Time Tracking Lithotripsy in the Single Renal Stone Treatment

An ultrasound-based real-time tracking system has been shown to improve the efficacy of lithotripsy in animal studies. This system has been implemented into an electromagnetic shockwave lithotripter (LM-9200 ELMA), and the treatment outcomes were prospectively evaluated. A total of 1332 patients with one renal stone were treated with LM-9200 ELMA lithotripter between December 2004 and November 2007. Fluoroscopy and ultrasound were alternately used for calculus localization and focusing first. After the calculus was focused and displayed clearly by ultrasound, the ultrasound-based real-time tracking system was applied for calculus monitoring and shockwave trigger control. All patients were followed for up to 3 months. Data regarding stone location, stone size, shockwave number, treatment time, stone free rate, and possible complications were obtained. Of the 865 males and 467 females treated (mean stone size = 12.3 mm), the stone-free rate in 3 months was 80.0%. For all patients, neither anesthetics nor analgesics were necessary. The incidence of blood pressure and microscopic hematuria grading increment at 2 weeks after treatment was 6.8% and 13.8%, respectively. There were no subcapsular hematoma or prolonged hematuria observed. Stone size was an important factor predicting stone-free rate (9.1 +/- 2.1 mm in the successful group vs. 22.0 +/- 3.1 mm in the failed group, p < 0.001). The calculated efficiency quotient of this machine was 0.67. An electromagnetic shockwave lithotripter using ultrasound-based real-time tracking system showed efficient crushing of renal calculi in vivo. Our experience has shown that patients treated by this lithotripter are safe with slight microscopic hematuria and having 80% chance of stone clearance.

Extracorporeal Shock Wave Lithotripsy (ESWL) for Obstructive Pancreatic Stones Causing Recurrent Acute Pancreatitis

Purpose: Obstructive pancreatic duct stones may cause recurrent acute pancreatitis and chronic abdominal pain. The use of ESWL for treatment of abdominal pain has been well documented; however, its effect on prevention of recurrent acute pancreatitis has not been studied. We evaluated the utility of ESWL for treatment of patients with recurrent acute pancreatitis caused by obstructive stones not amenable to endoscopic removal. Methods: Consecutive patients with recurrent acute pancreatitis due to obstructive pancreatic duct stones not amenable to endoscopic removal were prospectively evaluated. Stones were obstructive if during ERCP the duct proximal (upstream) to the stone could not be opacified by contrast or if opacification could be achieved only under pressure using an inflated extraction balloon. ESWL was performed by a pancreatologist (M.P.) using an electromagnetic shockwave lithotripter (Modulith SLX2, Storz Medical AG, Kreuzlingen, Switzerland). After ESWL, the patients were followed for recurrence of acute pancreatitis. Diagnosis of acute pancreatitis was based on guidelines proposed by the American College of Gastroenterology (Am J Gastroenterol 2006; 101:2379-2400). Results: Ten patients underwent 13 sessions of ESWL (range 1-3). The mean age was 54 years (range 44-72). The cause of chronic pancreatitis was alcohol abuse in 7 and idiopathic in 3 patients. Ductal calcifications were limited to the head of the gland in 4 patients. In 6 patients, the ductal calcifications were more extensive with involvement of the head, body and tail. The mean size of the largest stone in each patient was 1.5 cm (range 1-2 cm). Complete clearance was achieved in 7 (70%) patients. In the remaining 3 (30%) patients, ductal clearance was partial. However, relief of obstruction assessed by post procedure ERCP was achieved in all patients. The mean length of follow-up was 20 months (range 12-36). Three patients had recurrent acute pancreatitis during the follow-up period, caused by recurrence of obstructive stones in two and presence of main duct stricture in one. Conclusion: ESWL of obstructive pancreatic duct stones can prevent further attacks of acute pancreatitis. Recurrence of acute pancreatitis following ESWL may indicate stone recurrence or presence of strictures.