Bifocal reflector for electrohydraulic lithotripters

OBJECTIVE: To describe the design and construction of a bifocal reflector that could be used in electrohydraulic extracorporeal shockwave lithotripters in order to increase their efficiency. METHODS: The new reflector is obtained by joining two sectors of two rotationally symmetric ellipsoidal reflectors having different distances between their foci, which results in a bifocal composite reflector with the F1 foci in coincidence and the two F2 foci separated by a certain distance. As in conventional reflectors, shockwaves are generated by the electrical breakdown of water between two electrodes, located at the focus (F1) closest to the reflector. A prototype was constructed and tested in an experimental shockwave generator of our own make, using two different types of kidney-stone models, one to test the stone fragmentation abilities, and the other to test the stone pitting abilities. Fragmentation data for the new reflector were compared with those of a conventional ellipsoidal reflector tested on the same device. RESULTS: The new design appeared to be more efficient in breaking up both types of kidney-stone models than the conventional reflector. Pressure measurements were obtained with both reflectors using needle hydrophones. The physical background of shockwave reflection on both reflectors is also explained. CONCLUSION: With this new reflector, it could be possible, in principle, to reduce the treatment time of extracorporeal shockwave lithotripsy.     

Synchronous twin-pulse technique to improve efficacy of SWL: preliminary results of an experimental study.

BACKGROUND AND PURPOSE: Extracorporeal shockwave lithotripsy (SWL) is the treatment of choice for the majority of renal and ureteral stones. The Dornier HM3 lithotripter has good results but with some limitations and complications. A number of second- and third-generation machines have been developed employing different energy sources, focusing devices, and coupling media. These devices overcome some of the limitations and lessen the complications but at the expense of the success rate. Use of the consecutive double-pulse technique (as in the MFL 5000) and of combined under-table and over-table modules consecutively (as in the Siemens Lithostar Plus) improves the efficacy of fragmentation. The aim of this study was to study the effects of the use of synchronous twin pulses generated by under-table and over-table identical shockwave reflectors for stone fragmentation. MATERIALS AND METHODS: We designed a lithotripter with two identical shockwave generators and identical reflectors (twin heads). One reflector was under the table and fixed, while the second reflector was over the table and hangs on a C-arm so that the angle between the axes of the two reflectors could be changed. The second focal points (F2) of the two reflectors lay in the same position. A lucent lightweight acrylic water tank with one side sealed by a silicon rubber membrane was fixed to the SWL table so that the membrane coupled with the water cushions of both reflectors. The tank was filled with degassed water and the targeted material was fixed on a holder and immersed in the water so as to be at F2. Comparison of the use of one shockwave source and two shockwave sources simultaneously was done relative to: (1) cavitation effect on aluminum foil; (2) quality of disintegration, shape of the focal zone, and ideal position of F2 using ceramic blocks; and (3) disintegrative efficacy using dental bone cement. RESULTS: The cavitation effect became more localized with the use of two reflectors. Also, the volume and rate of stone disintegration increased with the use of the two reflectors, with production of fine (<2-mm) fragments. The focal zone became smaller and conical with no propagation of shockwaves beyond F2. These results were more evident if the angle between the axes of the reflectors was 90 degrees. CONCLUSION: This new technique of SWL may improve the efficacy of treatment of urinary tract stones. It also may be less harmful to the renal tissues, but animal experiments must be carried out to prove this.     

Pressure-release versus rigid reflector for extracorporeal shockwave lithotripsy

PURPOSE: To evaluate the advantages and disadvantages of using a pressure-release reflector instead of a rigid reflector to concentrate shockwaves for extracorporeal shockwave lithotripsy (SWL). MATERIALS AND METHODS: As in all electrohydraulic lithotripters, shockwaves were generated by electrical breakdown of water between two electrodes, located at the focus (F1) closest to a paraellipsoidal reflector. A pressure-release reflector, made out of polyurethane foam, was constructed and tested on a research lithotripter using kidney stone models. Fragmentation data and pressure measurements were compared with those of a conventional rigid reflector tested on the same device. RESULTS: The weight of stone model fragments remaining after shockwave exposure was less with the pressure-release reflector after screening through a 3.0 x 3.0-mm mesh. The residual fragment weight was less with the rigid reflector using 1.0 x 1.0- and 0.6 x 0.6-mm meshes. CONCLUSION: Pressure-release reflectors may maintain acceptable stone fragmentation while offering improved patient safety and should be considered for SWL.     

Conversion of an HM3 lithotripter into a research device

PURPOSE: To describe the conversion of a Dornier HM3 lithotripter into a research device and evaluate its performance. MATERIALS AND METHODS: A used HM3 lithotripter was donated to our university by the St. Thomas' Hospital in London. It was disassembled, shipped to our laboratory, partially assembled, and modified as a research lithotripter. Pressure measurements at several positions and kidney stone model fragmentation tests were performed to evaluate the modified system. Results were compared with information published by other authors and data obtained in our laboratory using another electrohydraulic research lithotripter. RESULTS: Pressure records showed typical lithotripter waveforms with a rapid rise to about 50 MPa, followed by decay to a negative peak of approximately 9 MPa. Maximum compressional peaks were obtained at F2 and 25 mm below F2. Kidney stone model fragmentation was typical for electrohydraulic shockwave lithotripters. CONCLUSIONS: Comparison of pressure measurements with data obtained by other authors on the same lithotripter several years ago indicate that the pressure waveform has not changed significantly. A much smaller water tank, a small X-Y-Z positioner, and no X-ray imaging system facilitate the use of this shockwave generator for in vitro experiments with small samples such as vials containing cell suspensions, having the advantage of a reliable, well-known, and well-characterized commercial shockwave generator.     

Reducing shock number dramatically decreases lesion size in a juvenile kidney model

BACKGROUND AND PURPOSE: Adult stone patients are treated with several thousand lithotripter shockwaves (SWs) in order to pulverize a kidney stone. This typical clinical dose assures that the stone will be fractured completely. However, this same dose induces damage to the kidney, especially pediatric-size kidneys. If increasing SW number is known to increase renal injury and functional impairment, will reducing SW number below typical treatment levels significantly decrease kidney damage and hemodynamic changes? MATERIALS AND METHODS: To address this question, one kidney in each of nine juvenile pigs (6-7 weeks old) was treated with 1000 SWs at 24 kV directed at a lower-pole calix with an unmodified HM-3 lithotripter. Parenchymal-lesion size was determined by sectioning the entire kidney and quantitating the amount of hemorrhage in each slice. Renal function was determined before and after SW treatment by inulin clearance, paraaminohippurate (PAH) extraction, and PAH clearance. The resulting morphologic and functional changes were then compared with those of kidneys that had been treated with a typical clinical dose of 2000 SWs (data previously published; J Am Soc Nephrol 2000;11:310). Eleven pigs were utilized as sham-treated controls. RESULTS: Limiting SW number to 1000 significantly reduced the size of the lesion (by 95%) and reduced the degree of functional change (glomerular filtration rate by 38%, PAH extraction by 73%, renal plasma flow by 46%) compared with kidneys receiving 2000 SWs (an adult dose). CONCLUSIONS: These data support the idea that SW number should be reduced to the lowest number that fractures kidney stones in order to minimize renal injury and functional impairment.     

Dual-head lithotripsy in synchronous mode: acute effect on renal function and morphology in the pig

OBJECTIVE: To assess the effect of dual-head lithotripsy on renal function and morphology in a pig model of shockwave (SW) injury, as lithotripters with two shock heads are now available for treating patients, but little information is available with which to judge the safety of treatment with dual pulses. MATERIALS AND METHODS: A dual-head electrohydraulic lithotripter (Duet, Direx Corp., Natick, MA, USA) was used to treat the lower renal pole of anaesthetized pigs with a clinical dose of SWs (2400 dual SWs; 10 kidneys) delivered in synchronous mode, i.e. both heads fired simultaneously. For comparison, pigs were treated with either 2400 SWs (12 kidneys) or 4800 SWs (eight) with a conventional electrohydraulic lithotripter (HM3, Dornier, Wessling, Germany). RESULTS: Dual-pulse SW treatment with the Duet lithotripter caused a decline in the mean (sd) glomerular filtration rate (GFR) of 4.1 (1.9) mL/min, with a trend for the effective renal plasma flow (RPF), at 31 (19) mL/min, to also decrease. These changes in renal haemodynamics were similar to the decreases in GFR and RPF in response to treatment with the HM3 lithotripter with 2400 SWs, at 4.8 (0.8) and 32 (10) mL/min, respectively, or 4800 SWs, at 5.4 (1.0) and 68 (14) mL/min, respectively. Linear association analysis showed that the functional response to dual-pulse SWs was more variable than with conventional SWs. Morphological quantification of kidney damage (expressed as a percentage of functional renal volume, FRV) showed that tissue injury with 2400 paired SWs with the Duet, at 0.96 (0.39)% FRV, was similar to injury produced by either 2400 single SWs, at 1.08 (0.38)% FRV, or 4800 single SWs, at 2.71 (1.02)% FRV, with the HM3. However, morphological damage was less consistent with the Duet (measurable in only five of eight kidneys) than that with the HM3 (measurable in all 12 kidneys). Acoustic output and the timing of dual SWs in synchronous mode increased in variability as the electrodes aged, affecting the amplitude and targeting of focal pressures. CONCLUSION: With the caveat that variability in the timing of dual SWs will unpredictably alter the distribution of SW energy within the kidney, this study shows that a clinical dose of dual-head SWs delivered in synchronous mode elicits a renal response similar to, but more variable than, that with a clinical dose of SWs from a conventional electrohydraulic lithotripter.     

A prototype device for nonimmersion shock wave lithotripsy using ultrasonography for calculus localization

Extracorporeal shock wave lithotripsy has revolutionized the clinical treatment of renal calculi. A device was constructed with a spark gap for shock wave generation and a water-filled ellipsoidal reflector to focus the shock wave energy. A membrane coupled the device to the pig and an ultrasonic transducer was used for stone visualization. Initial in vitro experiments and in vivo studies using dwarf pigs demonstrated fragmentation of calculi.     

Dual pulse shock wave lithotripsy: in vitro and in vivo study

PURPOSE: We evaluated the performance of a novel dual pulse lithotriptor for extracorporeal lithotripsy. MATERIALS AND METHODS: A piezoelectric lithotriptor was modified to produce pairs of successive (tandem) shock waves. Four kidney stone models were exposed in vitro to 500 single shock waves with a standard lithotriptor. Another set of stones was exposed 1 at a time to 250 pairs of shock waves with the tandem lithotriptor. The time delay between the first and second shock waves was increased in steps of 50 microseconds between 100 and 600 microseconds. Four stones were used per delay, ie 44 phantoms were fractured with the tandem system. Rabbits were used in vivo to demonstrate that the novel device does not produce more tissue trauma. Five rabbits were exposed to shock waves generated by the new device, 5 were treated with the standard system and 5 served as the sham treated group. Renal damage caused by the 2 systems was compared 1 week after shock wave application. RESULTS: Enhanced fragmentation efficiency was achieved at a delay of 250 microseconds. In vivo results indicate that the dual pulse shock wave generator does not produce more kidney tissue damage. CONCLUSIONS: Tandem lithotriptors may improve the quality and rate of stone comminution without increasing tissue damage. The device enhances cavitation induced damage to kidney stones. Extensive in vivo experiments will be important to evaluate the new design.     

Technical characterization of an ultrasound source for noninvasive thermoablation by high-intensity focused ultrasound

OBJECTIVE: To develop a generator for high-intensity focused ultrasound (HIFU, a method of delivering ultrasonic energy with resultant heat and tissue destruction to a tight focus at a selected depth within the body), designed for extracorporeal coupling to allow various parenchymal organs to be treated. MATERIAL AND METHODS: The ultrasound generated by a cylindrical piezo-ceramic element is focused at a depth of 10 cm using a parabolic reflector with a diameter of 10 cm. A diagnostic B-mode ultrasonographic transducer is integrated into the source to allow the focus to be located in the target area. The field distribution of the sound pressure was measured in degassed water using a needle hydrophone. An ultrasound-force balance was used to determine the acoustic power. These measurements allowed the spatially averaged sound intensity to be calculated. The morphology and extent of tissue necrosis induced by HIFU was examined on an ex-vivo kidney model. RESULTS: The two-dimensional field distribution resulted in an approximately ellipsoidal focus of 32 x 4 mm (- 6 dB). The spatially maximum averaged sound intensity was 8591 W/cm2 at an electrical power of 400 W. The lesion caused to the ex-vivo kidney at this maximum generator power with a pulse duration of 2 s was a clearly delineated ellipsoidal coagulation necrosis up to 8.8 x 2.3 mm (length x width) and with central liquefied necrosis of 7.9 x 1.9 mm. CONCLUSION: This newly developed ultrasound generator with a focal length of 10 cm can induce clear necrosis in parenchymal tissue. Because of its specific configuration and the available power range of the ultrasound generator, there is potential for therapeutic noninvasive ablation of tissue deep within a patient's body.     

Percutaneous stone implantation in the pig kidney: a new animal model for lithotripsy research

PURPOSE: This report describes a new animal model for research on the parameters of shockwave delivery and the mechanisms of shockwave action in SWL. MATERIALS AND METHODS: Female pigs (approximately 45 kg) were anesthetized for creation of an upper pole peripheral caliceal access. The tract was dilated with a 30F Nephromax balloon and Amplatz sheath, and a 24F rigid nephroscope was used to guide a gypsum artificial stone into a lower pole calix. An internal ureteral stent was then placed. After a 2-hour recovery period, lithotripsy was performed using an unmodified Dornier HM3 lithotripter. Following SWL, en bloc excision of the urinary tract was performed, and the stone fragments were collected. RESULTS: As observed by nephroscopy, most stones were surrounded by urine that was free of clot or debris. Urine output was >1 mL/kg per minute by the time the animal was positioned for SWL after a 2-hour observation period. When the conditions of shockwave (SW) exposure were 400 SWs, 20 kV, and 120 SW/min, the efficiency of stone fragment recovery was 85% +/- 2% (N = 6 stones). CONCLUSIONS: This procedure provides a minimally invasive method for placement of model stones of clinically relevant size within the pig kidney. Stone implantation is efficient and permits experiments to be conducted in 1 day. Stone fragmentation can be quantitated, and the animal can serve as its own control. Long-term experiments are also feasible. Overall, this new animal model is appropriate for experimentation on the parameters of SW delivery in SWL.     

Recent developments in SWL physics research

Two projects in our laboratory highlight some recent developments in shockwave lithotripsy (SWL) physics research. In the first project, we developed a prototype of a piezoelectric annular array (PEAA) shockwave generator that can be retrofitted on a Dornier HM-3 lithotripter for active control of cavitation during SWL. The PEAA generator, operating at 15 kV, produces a peak positive pressure of approximately 8 MPa with a -6-dB beam diameter of 5 mm. The shockwave generated by the PEAA was used to control and force the collapse of cavitation bubbles induced by a laboratory electrohydraulic shockwave lithotripter with a truncated HM-3 reflector. With optimal time delay between the lithotripter pulse and the PEAA-generated shockwave, the collapse of cavitation bubbles near the stone surface could be intensified, and the resultant stone fragmentation in vitro could be significantly improved. In the second project, high-speed shadowgraph imaging was used to visualize the dynamics of lithotripter-induced bubble oscillation in a vascular phantom. Compared with the free bubble oscillation in water, the expansion of cavitation bubble(s) produced in silicone tubes and a 200-microm cellulose hollow fiber by either a Nortech EHL or a Dornier XL-1 lithotripter was found to be significantly constrained. Rupture of the cellulose hollow fiber was observed consistently after about 20 shocks from the XL-1 lithotripter at an output voltage of 20 kV. These results confirm experimentally that SWL-induced cavitation in vivo can be significantly constrained by the surrounding tissue, and large intraluminal bubble expansions could cause rupture of capillaries and small blood vessels.     

Original lithotomy positioning for transperineal extracorporeal shockwave lithotripsy for distal ureteric calculi with Tripter X1.

Extracorporeal shockwave lithotripsy (ESWL) has been initially designed for stones located in the kidney and the upper ureter. Our lithotripter is no exception. Its components (the table and the orientation of the semi-ellipsoid reflector) are adapted for the treatment of kidney or lumbar ureter stones. However, the elements forming the unit of treatment (the table, the C-arm and the Tripter) can be modified in such a way that focalization of stones of the lower ureter becomes possible through a perineal exposure. The aim is to avoid the pelvic bone shield while a good focalization of the stone is realized. From June 1989 to March 1991, 35 patients were treated for distal ureteric stones by ESWL in this original positioning.     

不同冲击波源及次数致家兔肾损伤的比较研究

目的探讨不同冲击波源及冲击次数对肾损伤的差异。方法40只健康雄性家兔,按波源分为电磁组和液电组,分别冲击1000次、1500次分为A、B亚组。冲击前、后不同时间测定血清黄嘌呤氧化酶（XOD）、谷胱甘肽-过氧化物酶（GSH-PX）、抗超氧阴离子自由基,并观察肾脏组织学变化。结果各组血清XOD冲击后即刻升高,72h达峰值（P〈0.01）,14d降至正常水平。GSH-PX、抗超氧阴离子自由基于冲击后24h明显下降,72h降至最低值（P〈0.01）,2周后恢复冲击前水平。A亚组各指标在冲击后24h至7d与B亚组有显著性差异（P〈0.01）;液电及电磁冲击波源之间各指标未见显著性差异。组织学改变在冲击后24h至72h表现损伤最为显著,14d后基本恢复正常。结论冲击波导致的肾损伤程度与冲击次数呈正相关,在保证碎石效果的前提下控制冲击次数可有效减轻肾损伤。液电和电磁两种冲击波源导致肾损伤程度无明显差异。     

Complications of pneumatic ureterolithotripsy in the early postoperative period

PURPOSE: To document the perioperative and early postoperative complications of pneumatic ureterolithotripsy. PATIENTS AND METHODS: Between January 1997 and December 2003, pneumatic ureterolithotripsy was performed in 665 male and 314 female patients for stones >0.5 cm. The age range was 9 months to 72 years (mean 41 years). Preoperatively, intravenous urography, urinalysis, and urine culture were done. Cefepime 1 g was given as prophylactic antimicrobial therapy 1 hour prior to surgery. A plain film of the urinary tract was taken immediately before the procedure. The operations were carried out with the patient under general anesthesia. Rigid ureteroscopes (6.9F ACMI "micro-6" or 8F-10F Storz) and the Vibrolith (Elmed, Ankara, Turkey) pneumatic lithotripter were used. The fragments were extracted with forceps or baskets. Urinalysis and culture as a routine postoperative evaluation and a plain film or ultrasonogram of the urinary tract when needed were done 1 week after the procedure. RESULTS: The stones were completely removed in 847 patients (86.5%); 783 (80%) of them went home on the day of surgery. A ureteral stent was needed in 401 patients (41.0%). Perioperative complications were migration of the stone into the kidney in 70 patients (7.2%), mucosal damage in 34 (3.5%), ureteral perforation in 17 (1.7%), ureteral avulsion in 4 (0.4%), and conversion to open surgery in 3 (0.2%). During the early postoperative period, flank pain (18.4%), pelvic discomfort (5.5%), macroscopic hematuria (7.3%), and urinary tract infection (5%) were recorded. CONCLUSION: Ureterolithotripsy by a pneumatic lithotripter is a minimally invasive, highly tolerable procedure with a low complication rate and short hospital stay when performed meticulously with appropriate instruments.     

The efficacy and parenchymal consequences of extracorporeal shock wave lithotripsy in infants

OBJECTIVES: To determine the efficacy of extracorporeal shock-wave lithotripsy (ESWL) in young children and to evaluate, using renal scintigraphy, any possible adverse effects on renal parenchyma. PATIENTS AND METHODS: From January 1991 to October 1998, 19 infants (aged 5-24 months) underwent ESWL for kidney urolithiasis using a Sonolith 3000 (14 kV, Technomed Corp, Lyon, France) or a Nova (14-20 kV, Direx Medical Systems, Paris, France) lithotripter. The treatment and its effects were evaluated using a physical examination, conventional imaging (plain abdominal X-ray and ultrasonography) and renal scintigraphy 24 h before ESWL and again at least 6 months after the last session of treatment. RESULTS: Ten children were rendered stone-free by ESWL after one session and 18 after two sessions. At the follow-up (8 months to 8 years, mean 36 months) no hypertension was recorded and no acquired parenchymal damage was detected with conventional imaging. No scars or significant variation of differential function attributable to ESWL were identified on renal scintigraphy. CONCLUSION: ESWL is clearly effective for treating infant urolithiasis. There were no renal parenchymal lesions associated with ESWL, even in previously damaged kidneys or after the treatment of staghorn calculi. A long-term follow-up (assessing blood pressure) is mandatory and renal scintigraphy before and 6 months after ESWL in infants is recommended to confirm these results in a larger series.     

Efficacy of the Duet lithotripter using two energy sources for stone fragmentation by shockwaves: an in vitro study

PURPOSE: To evaluate the efficacy of the Duet lithotripter's novel design of two independent spark-plug generator/reflector systems focused at a common F2. The apparatus allows either simultaneous delivery of shockwaves from both generators (resulting in a per-shock energy delivery at F2 equal to that delivered by its single generator at about 24 kV), alternating (between the two generators), or single-generator delivery of shockwaves at various energy levels and rates. MATERIALS AND METHODS: Eighty-five phantom gypsum stones (volume 786 mm3 each) were placed in a net-like basket and immersed in a specially designed waterbath coupled with the Duet lithotripter (Direx Medical Systems Ltd., Petach Tikva, Israel). Shockwaves were delivered at rates of either 60 or 120 per minute and at intensities of 16 or 22.8 kV (electrohydraulic). Energy was delivered either separately from each generator, in an alternating mode, or simultaneously from both generators. The number of shocks required to fragment the stones sufficiently to allow all of the pieces to fall through the basket holes (complete fragmentation) was recorded. RESULTS: The number of shocks required for complete fragmentation in the alternate mode (120 shocks/min, each generator rate 60/min; 22.8kV) was lower than with the single generator, 112 +/- 19 v 134 +/- 18 (at a rate of 120/min; 22.8 kV). The simultaneous mode of dual generator shockwave delivery was more effective than the traditional single generator (114 +/- 28 shocks at a rate of 120/min, 16 kV v 159 +/- 40 shocks at a rate 120/min; 22.8kV). CONCLUSION: The Duet lithotripter is more effective when used in a simultaneous or alternating mode than is the classical single mode of shock delivery, with the added benefit of shorter treatment time.     

Utilization of multiple SAVI SCOUT surgical guidance system reflectors in the same breast: A single‐institution feasibility study

SAVI SCOUT Surgical Guidance System has been shown to be a reliable and safe alternative to wire localization in breast surgery. This study evaluated the feasibility of using multiple reflectors in the same breast. We performed an IRB‐approved, HIPAA‐compliant, single‐institution retrospective review of 183 patients who underwent breast lesion localization and excision using SAVI SCOUT Surgical Guidance System (Cianna Medical) between June 2015 and January 2017. We performed a subset analysis in 42 patients in whom more than one reflector was placed. Specimen radiography, pathology, distance between reflectors, target removal, margin positivity, and complications were evaluated. Among 183 patients, 42 patients had more than one reflector placed in the same breast to localize 68 lesions. Benign (n = 6, 8.8%), high‐risk (n = 23, 33.8%), and malignant (n = 39, 57.4%) lesions were included. Thirty‐six patients (85.7%) had a total of 2 reflectors placed and 6 patients had a total of 3 reflectors placed (14.3%). The indications for multiple reflector placement in the same breast included multiple separate lesions (n = 23) and bracketing of large lesions (n = 19). The mean distance between the reflectors was 42 mm (22‐93 mm). All lesions were successfully targeted and retrieved. Of 39 malignant lesions, 10.3% (n = 4) had positive margins and 10.3% (n = 4) had close (<1 mm) margins at surgery. All patients with positive margins underwent re‐excision. No complications occurred preoperatively, intra‐operatively, or postoperatively. The use of multiple SAVI SCOUT reflectors for localizing multiple lesions in the same breast or bracketing large lesions is feasible and safe.     

In-Vivo relation between CT attenuation value and shockwave fragmentation

PURPOSE: To use CT attenuation numbers as a means of determining the susceptibility of an artificial stone to in-vivo fragmentation with extracorporeal shockwave lithotripsy (SWL). MATERIALS AND METHODS: Four types of artificial kidney stones having different CT attenuation values were used. One randomly selected stone was implanted in the renal pelvis of a kidney of 12 young pigs and exposed in vivo to 2500 shockwaves (21 kV) using an electrohydraulic lithotripter. Bilateral nephrectomy was performed after SWL. Fragments were strained through a mesh with a 3.1-mm grid, and the debris left on the mesh was dried and weighed. Fragmentation coefficients (FCs) were associated with CT attenuation values using a statistical model. RESULTS: The relation between FC and CT number was significant, indicating that as CT attenuation increases, FC is reduced. Larger stone fragments were obtained from stones with higher CT numbers. Initial stone weight was not a significant explanation for variations in FC. CONCLUSION: The CT values could be helpful in selecting patients for SWL in the future. However, other parameters such as stone porosity, shape, and roughness also will have to be considered.     

Extracorporeal shock wave lithotripsy with a transportable electrohydraulic lithotripter: experience with >300 patients

OBJECTIVE: To review a multicentre experience of using a transportable lithotripter (STS-T, Medstone, Inc, Aliso Viejo, CA. USA) for treating patients with urolithiasis in all parts of the urinary tract. PATIENTS AND METHODS: In all, 326 patients with a total of 370 stones were treated as outpatients with the STS-T lithotripter. All patients received a single shock wave lithotripsy treatment and were followed after 4-6 weeks in the outpatient clinic, the primary endpoint being to determine the efficacy (as defined by the stone-free rate). Secondary objectives included establishing a database of patient demographic information, stone characteristics, stone location, procedural endpoints, and complication rates. RESULTS: In all there were 370 procedures, with a mean of 2394 shocks administered at an energy level of 24 kV. The mean treatment time was 51 min, excluding anaesthesia-induction time. The mean stone aggregate size was 8.2 mm; 62% of the stones were in the kidney while 38% were in various locations in the ureter. Of the treated stones, 90% had definite or probable evidence of fragmentation. The overall stone-free rate after one treatment with the STS-T was 52.8%. Of patients with residual fragments, most (61%) had fragments of <4 mm in aggregate diameter. The overall complication rate was 3.8%, the most common complication being postoperative pain. CONCLUSION: The Medstone STS-T lithotripter was an effective device for treating urolithiasis in all parts of the urinary tract. This system had a high margin of safety, as shown by the low complication rate. With no apparent sacrifice of efficacy compared to first-generation or fixed (not transportable) second-generation devices, the Medstone STS-T represents an important advance in the development of a truly transportable lithotripter.     

Urolithiasis--a change in therapeutic methods extracorporeal shock wave lithotripsy using a Dornier kidney lithotripter HM3

The kidney stone of less than 2 cm can be effectively treated by extracorporeal shock wave lithotripsy (ESWL) using a Dornier kidney lithotripter HM3 without any complication that might need other therapy. However, in the case of a large kidney stone and ureteral stone, there are some difficulties in the treatment with ESWL. To obtain better results for these stones with a Dornier kidney lithotripter HM3, in the patient having a large stone a double-J stent was placed and ureteral catheter was indwelling for the ureteral stone before ESWL. In some cases high frequency positive pressure ventilation (HFPPV) was applied to make respiratory movement of the stone minimum. An indwelling double-J stent can significantly decrease the necessity of auxiliary treatment and the incidence of high fever attack. Manipulation of a ureteral stone with a ureteral catheter did not facilitate stone disintegration, and also the success rate as compared with in situ ESWL. HFPPV can decrease the stone movement within 2 mm judged on the X-ray monitor and increase the effectiveness of the shock wave on the stone, leading to minimize not only shock wave dose but also side effects from shock wave exposure.