First clinical experience with a Q-switched neodymium:YAG laser for urinary calculi

Analysis of stones formed in the human gall bladder and kidney using advanced spectroscopic techniques

Stone diseases (gallstones and kidney stones) are extremely painful and often cause death. The prime aim of biomedical research in this area has been determination of factors resulting in stone formation inside the gallbladder and urinary tract. Many theories have been put forward to explain the mechanism of stone formation and their growth; however, their complete cycle of pathogenesis is still under debate. Several factors are responsible for stone formation; however, much emphasis is placed on the determination of elemental and molecular composition of the stones. In the present review article, we describe different kinds of spectroscopic techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF) spectroscopy, time-of-flight secondary ion mass spectrometry (TOF-SIMS), and laser-induced breakdown spectroscopy (LIBS) and highlight their use in the analysis of stone diseases. We have summarized work done on gallstones and kidney stones using these advanced techniques particularly over the last 10 years. We have also briefly elaborated the basics of stone formations inside the human body and their complications for a better understanding of the subject.

Exploring Laser-Induced Breakdown Spectroscopy as a Potential Tool in Mohs Micrography: A Mini Review

Mohs micrographic surgery is the technique of surgically removing skin tumors by gradually excising thin layers and visualizing under a microscope till a tumor-free zone is obtained. During the surgical procedure, visible tumors are surgically removed. During the second stage, if tumor margins are clear with the positive specimen at depth, only depth cavitations need to be done without altering the tumor diameter. Defining the depth during this procedure is a major challenge due to the nonexistence of proper guidelines. Using the laser-induced breakdown spectroscopy (LIBS) technique, depth profiling can be performed precisely, preventing excessive tissue removal and reducing time consumption during the microscopic examination.

Kidney stone analysis techniques and the role of major and trace elements on their pathogenesis: a review

Kidney stone disease is a polygenic and multifactorial disorder with a worldwide distribution, and its incidence and prevalence are increasing. Although significant progress has been made in recent years towards identifying the specific factors that contribute to the formation of kidney stone, many questions on the pathogenesis of kidney stones remain partially or completely unanswered. However, none of the proposed mechanisms specifically consider the role(s) of the trace elements and, consequently, the contribution of trace constituents to the pathogenesis of kidney stones remains unclear and under debate. The findings of some studies seem to support a role for some major and trace elements in the initiation of stone crystallization, including as a nucleus or nidus for the formation of the stone or simply as a contaminant of the stone structure. Thus, the analysis of kidney stones is an important component of investigations on nephrolithiasis in order to understand the role of trace constituents in the formation of kidney stones and to formulate future strategies for the treatment and prevention of stone formation and its recurrence. The aim of this review is to compare and evaluate the methods/procedures commonly used in the analysis of urinary calculi. We also highlight the role of major and trace elements in the pathogenesis of kidney stones.

Is the holmium:YAG laser the best intracorporeal lithotripter for the ureter? A 3-year retrospective study

PURPOSE

To study the efficiency and safety of holmium:YAG laser lithotripsy for ureteral stones.

PATIENTS AND METHODS

A series of 188 patients with 208 ureteral stones were treated with semirigid ureteroscopy and holmium:YAG laser lithotripsy from January 2003 to December 2005. Of the stones, 116 were lower ureteral, 37 middle ureteral, and 55 upper ureteral.

RESULTS

The success rate was 92.7% at the time of ureteroscopy and 96.7% at 3 months. The failures were secondary to retropulsion of the stones (3.3%). There were no perforations and one stricture. Stenting was done in 90% of patients.

CONCLUSIONS

The Holmium:YAG laser is an ideal intracorporeal lithotripter for ureteral calculi, with a high success rate and low morbidity.

Hollow fiber optics with improved durability for high-peak-power pulses of Q-switched Nd:YAG lasers

To improve the damage threshold of hollow optical waveguides for transmitting Q-switched Nd:YAG laser pulses, we optimize the metallization processes for the inner coating of fibers. For silver-coated hollow fiber as the base, second, and third Nd:YAG lasers, drying silver films at a moderate temperature and with inert gas flow is found to be effective. By using this drying process, the resistance to high-peak-power optical pulse radiation is drastically improved for fibers fabricated with and without the sensitizing process. The maximum peak power transmitted in the fiber is greater than 20 MW. To improve the energy threshold of aluminum-coated hollow fibers for the fourth and fifth harmonics of Nd:YAG lasers, a thin silver film is added between the aluminum film and the glass substrate to increase adhesion of the aluminum coating. By using this primer layer, the power threshold improves to 3 MW for the fourth harmonics of a Q-switched Nd:YAG laser light.

Hollow-waveguide-based nanosecond, near-infrared pulsed laser ablation of tissue

BACKGROUND AND OBJECTIVE

Short-pulse solid-state lasers have recently received much attention as new coherent light sources for medical applications, but steady transmission of their high-energy output pulses through a solid quartz fiber is difficult because of the onset of laser-induced breakdown. We previously demonstrated that hollow waveguides could be used to deliver nanosecond laser pulses for tissue ablation. The aim of this study was to determine the optimum laser pulse energy and range of defocused distance for obtaining a deep and sharp ablation channel in myocardial tissue with laser pulses transmitted through a hollow waveguide.

STUDY DESIGN/MATERIALS AND METHODS

Cyclic-olefin-polymer-coated silver hollow waveguides of 1 mm in inner diameter and 1 m in length were used. A vacuum-cored scheme was applied to the waveguides to suppress laser-induced air breakdown. Porcine myocardial tissue was irradiated with 300 laser pulses that were delivered through the waveguide in vitro at various laser energy levels and defocused distances, and depths and diameters of channels were measured. Histological analysis of the ablated tissues was also performed.

RESULTS

At an ablation energy of approximately 60 mJ/pulse, deep (>4.5 mm) and sharp (depth-to-diameter ratio of > 6) channels were created in tissue in the range of defocused distances of -4 approximately + 0.5 mm. Under these conditions, waveguide bending did not cause a remarkable change in ablation characteristics. Histological analysis of ablated tissue showed limited thermal damage but suggested a certain extent of mechanical effects in the tissue.

CONCLUSION

With near-infrared, nanosecond laser pulses delivered through a cyclic-olefin-polymer-coated silver hollow waveguide, efficient and sharp ablation of myocardial tissue can be achieved, suggesting the usefulness of the hollow waveguide as a new flexible delivery system for high-intensity laser pulses.

The evolution and progress of ureteroscopy

Technology and refinements in urology have prospered with the bonding of engineers and surgeons. The introduction of fiberoptics and the development of the ureteroscope opened the doors to the field of ureteroscopy. Advances in rigid and flexible ureteroscopy with irrigating and working channels have expanded the capability of the urologist to diagnose and treat most abnormalities of the upper tracts in adult and pediatric populations. Instrument development has easily paralleled the growth and development of the ureteroscope and has improved success, patient safety, and comfort with the incorporation of access sheaths, nitinol materials, and Ho:YAG laser technology. Owing to their minimal morbidity and high success rate, ureteroscopic evaluation and therapeutic interventions in the upper tract represent the gold standard of management. Albert Einstein said, "There are only two ways to live your life. One is as though nothing is a miracle. The other is as though everything is a miracle." Contemporary ureteroscopy is a historical miracle that has opened a vista of endless limits in upper tract endoscopy (Fig. 4, Box 1).

Laser Lithotripsy for Treatment of Canine Uroliths

OBJECTIVE

To confirm in vivo optimal laser energy settings previously determined in vitro for lithotripsy, to develop a technique for Ho:YAG laser lithotripsy, and to evaluate acute and chronic tissue effects of laser lithotripsy.

STUDY DESIGN

Prospective, randomized preclinical trial.

ANIMALS OR SAMPLE POPULATION

Nineteen intact, adult male dogs.

METHODS

Via cystotomy, a single urolith was inserted into the urethra to the level of the base of the os penis to simulate obstruction. Uroliths (calcium oxalate, urate, or magnesium ammonium phosphate) were fragmented by Ho:YAG laser, in contact mode through a 320 micro optic fiber, passed through the operating channel of a 2.8 mm flexible endoscope. The time and total energy to fragmentation were recorded. Dogs were euthanatized immediately after lithotripsy (3 dogs) or at 3 days (7 dogs), and urethral lesions and any stone remnants were evaluated. Urethral integrity was also evaluated in 9 other dogs by endoscopy on day 10; these were also monitored clinically for 30 days.

RESULTS

The mean time for adequate fragmentation was 166.7 seconds (range, 47-494.5 seconds). The mean+/-SD energy used was 1418+/-851.2 J. In part 1, 2 dogs were obstructed with urolith fragments at necropsy. Eight dogs had minimal (<30 mg) or no urolith material evident within the urethra. Four dogs had gross focal or circumferential erosion, ulceration, or hemorrhage of the urethral mucosa. Lesions were not associated with the site of laser irradiation in 2 dogs. In dogs observed for 30 days, hematuria, pollakiuria, and stranguria that were observed after lithotripsy, resolved in all affected dogs by day 5. No mucosal lesions were observed by endoscopy and none of the dogs became obstructed.

CONCLUSION

Laser lithotripsy with the Ho:YAG laser in contact mode successfully fragmented obstructive uroliths in male dogs.

CLINICAL RELEVANCE

Laser lithotripsy may be a clinically relevant technique for treatment of urolithiasis in male dogs; clinical studies to evaluate long-term effects on urethral mucosa and the role of repeat treatment for recurrence are indicated.

Endoscopic lithotripsy with a new device combining ultrasound and lithoclast

BACKGROUND AND PURPOSE

Endoscopic lithotripsy is still the method of choice for a number of stones, especially large stones. Various disintegration techniques exist. We investigated the combination of two of these techniques: ultrasound and pneumatic lithotripsy.

PATIENTS AND METHODS

Fourteen consecutive patients with renal and one patient with bladder stones were treated with this new device. Ultrasound and pneumatic lithotripsy could be used independently or simultaneously.

RESULTS

Disintegration and stone removal was fast. The use of forceps or other instruments could generally be avoided. No complications attributable to the lithotripsy device were observed.

CONCLUSION

The combined ultrasound/pneumatic lithotripsy device is safe and highly effective. It reduces treatment time and enhances surgeon's comfort.

A perspective on laser lithotripsy: the fragmentation processes

This paper describes in simple terms the physics of laser-calculus interactions and introduces a method with which physicians can understand or evaluate the application of any new laser technique for use in lithotripsy or other medical fields. Tissue optical properties and laser parameters govern the mechanism(s) of fragmentation of urinary or biliary calculi. Laser pulse energies for clinical lithotripsy range from Q0 = 20 mJ to 2 J for short-pulsed lasers to long-pulsed lasers, respectively. Lasers with short pulse durations (i.e., less than a few microseconds) fragment calculi by means of shockwaves following optical breakdown and plasma expansion of ionized water or calculus compositions or by cavitation collapse, thus manifesting a photoacoustical effect. Laser-tissue interactions involving dominant photomechanical or photoacoustical effects are usually stress confined. Long-pulsed lasers (i.e., >100 microsec), on the other hand, generate minimal acoustic waves, and calculi are fragmented by temperatures beyond the thresholds for vaporization of calculus constituents, melting, or chemical decomposition.

Update on contact lithotripsy

Despite the development of extracorporeal shockwave lithotripsy, endoscopic stone removal, with or without intracorporeal lithotripsy, is still an effective minimally invasive alternative for special indications. There is no defined all-purpose lithotripsy procedure for contact lithotripsy. The choice of the lithotripsy procedure for endoscopic stone disintegration depends on a number of different factors, the main one being stone localization. Small calibre, flexible probes (electrohydraulic, pneumatic, laser) are especially appropriate for ureterorenoscopy, but the speed of stone disintegration is a limiting factor. In contrast, large calibre rigid probes (ultrasound) are clearly more effective, but are unsuitable in size for flexible ureterorenoscopy. This indicates that the type and size of the endoscope decisively influences the choice of devices for endoscopic stone disintegration. Additional inhibiting factors are the flexibility or the rigidity of the instrument and the diameter of the working channel. It must be noted that total costs are not only calculated on the purchase of the equipment, but must also cover disposable materials.

Intracorporeal lithotripsy with the Alexandrite laser

BACKGROUND AND OBJECTIVE

The objective of this study was to evaluate clinical use of an Alexandrite laser lithotripter for intracorporeal lithotripsy of urinary calculi.

STUDY DESIGN/MATERIALS AND METHODS

We prospectively evaluated a flash lamp pumped, Q-switched Alexandrite solid-state laser for use in conjunction with ureteroscopy (30 cases) or percutaneous nephrolithotripsy (2 cases). The laser operates at a wavelength of 755 nm in a pulsed mode with pulses of 150-800 ns duration at energy settings of 30-80 mJ.

RESULTS

The fragmentation rate with the Alexandrite laser alone was 50% (16/32). Failure of the laser was due to equipment malfunction or technical problems in 11 cases and inability to fragment the stone in 5. All cases of failed Alexandrite laser lithotripsy were successfully salvaged with alternative modalities of endoscopic stone destruction and removal. One intraoperative complication, a ureteral perforation, occurred; however, no long-term sequelae related to laser use was documented.

CONCLUSION

Clinical results with the Alexandrite laser appear to be inferior to those reported with Alternative laser systems and other forms of intracorporeal lithotripsy. Whereas some of the inadequacies we have noted may be addressed in the future by modifications in the unit and delivery systems, we would not recommend this device for intracorporeal lithotripsy of urinary calculi in its current form.

Intracorporeal lithotripsy. Update on technology

The number and variety of devices currently available for endoscopic lithotripsy reflect the reality that no single device is ideal in all situations. Although the search for the universal lithotriptor continues, the urologist must consider several factors if faced with the decision of which device to purchase. Perhaps foremost among these factors is the clinical situation with which one commonly deals. For example, although the smaller, flexible probes such as EHL or laser demonstrate considerable utility if used ureteroscopically, the larger stone burden associated with today's percutaneous nephrolithotripsy population often is treated more efficiently with one of the mechanical devices employing a larger, rigid probe, such as ultrasound or the Lithoclast. Similarly, the type and size of endoscopic equipment at one's disposal have a significant impact on which device to purchase or use. There are physical constraints affecting which device may or may not be used, rigid versus flexible endoscope, working channel caliber, and offset versus end-on-port. The skill and experience of the surgeon is also a factor of obvious importance, particularly if one is using a modality with a relatively narrow margin of safety such as EHL. Likewise, the training and experience of nursing personnel is a factor, especially regarding the use of lasers, which require certified personnel who are well versed in laser safety. Finally, in today's environment one must carefully evaluate cost in terms of not only initial capital outlay but also ongoing charges for disposable and maintenance items. Thus, the decision of which device to purchase is complex and requires careful evaluation of all of the previously noted variables. Likewise, if one is fortunate enough to have more than one device available, the decision of which lithotriptor to employ requires a similar decision based on sound surgical judgment.

Free electron laser lithotripsy: threshold radiant exposures

PURPOSE

To determine the threshold radiant exposures (J/cm2) needed for ablation or fragmentation as a function of infrared wavelengths on various urinary calculi and to determine if there is a relation between these thresholds and lithotripsy efficiencies with respect to optical absorption coefficients.

MATERIALS AND METHODS

Human calculi composed of uric acid, calcium oxalate monohydrate (COM), cystine, or magnesium ammonium phosphate hexahydrate (MAPH) were used. The calculi were irradiated in air with the free electron laser (FEL) at six wavelengths: 2.12, 2.5, 2.94, 3.13, 5, and 6.45 microm.

RESULTS

Threshold radiant exposures increased as optical absorption decreased. At the near-infrared wave-lengths with low optical absorption, the thresholds were >1.5 J/cm2. The thresholds decreased below 0.5 J/cm2 for regions of high absorption for all the calculus types. Thresholds within the high-absorption regions were statistically different from those in the low-absorption regions, with P values much less than 0.05.

CONCLUSIONS

Optical absorption coefficients or threshold radiant exposures can be used to predict lithotripsy efficiencies. For low ablation thresholds, smaller radiant exposures were required to achieve breakdown temperatures or to exceed the dynamic tensile strength of the material. Therefore, more energy is available for fragmentation, resulting in higher lithotripsy efficiencies.

Principles and applications of laser lithotripsy: experience with the holmium laser lithotrite

INTRODUCTION AND OBJECTIVES

The initial clinical experience with holmium laser energy applied for endoscopic lithotripsy was positive. The current study is presented as a contrast to the preliminary findings and as a means of defining the clinical usefulness of this specific laser lithotrite.

MATERIALS AND METHODS

Calculi were treated endoscopically with the holmium laser lithotriptor and data was gathered prospectively. The youngest patient in the series was a thirteen-month--old who underwent percutaneous therapy, while the youngest patient on whom a retrograde endoscopic procedure was performed was a six-year old male patient with a proximal ureteral calculus. Lower water density, quartz fibers delivery systems were developed and employed. Fiber diameters ranged from 200-1000 micrograms. The smaller fibers were employed most commonly through the actively deflectable, flexible endoscope to facilitate treatment with maximum deflection. Larger fibers, with their much larger vaporization bubbles, were used through rigid endoscopes to debulk large stone burdens.

RESULTS

A total of 210 patients with 249 calculi were treated. All major stone compositions were treated with minimal variation in laser efficiency. All but three of 109 ureteral calculi were treated in a retrograde fashion to completion (i.e., "stone free") in one sitting (97%). One-hundred thirteen renal stone burdens were treated with the holmium laser; 99 of these were treated solely in a retrograde fashion. Of the latter, 79 (80%) required only a single session. The combination of the actively deflectable, flexible ureteroscope and the 200-micrograms fiber facilitated treatment to completion of 38 to 45 lower-pole caliceal calculi (85%). The success of ureteropyeloscopic lithotripsy with the holmium laser for all intrarenal calculi, including staged or second sitting for large complex stone burdens, was 90%. Sixteen percutaneous procedures (13 renal and 3 ureteral calculi) employed the holmium laser as an endoscopic lithotrite. All 28 patients with large bladder calculi with a mean diameter of 41.8 mm were treated to completion in one sitting. Complications from holmium laser energy, including postoperative ureteral stricture disease, were not encountered in this series.

CONCLUSIONS

Holmium laser energy is uniquely suited to treat urinary calculi safely regardless of stone size, location, or metabolic composition, and has particular efficacy in complex clinical presentations.

Safety and efficacy of the Alexandrite laser for the treatment of renal and ureteral calculi

OBJECTIVES

To assess the safety and efficacy of the Alexandrite laser for intracorporeal lithotripsy of renal and ureteral stones in conjunction with ureterorenoscopy or percutaneous nephrostolithotomy.

METHODS

We retrospectively analyzed the records of 137 patients with 169 calculi in 143 renoureteral units who were treated with the Alexandrite laser via a retrograde (91.5%) or antegrade (8.5%) endoscopic approach.

RESULTS

Adequate intraoperative fragmentation of the stone was observed in 88.8% of the cases. No intraoperative complications were attributable to the laser. At a mean follow-up of 34 days, the overall stone-free rate was 74.4%. The stone-free rate for ureteral stones (n = 115) was 80%, whereas the stone-free rate for renal stones (n = 22) was only 44%. In the best subgroup of ureteral stones (10 mm or less in the distal ureter), the stone-free rate was 97.4%.

CONCLUSIONS

The Alexandrite laser is a safe modality for intracorporeal lithotripsy and is highly effective for ureteral stones less than 10 mm in size.

Treatment of ureteric stones. Comparison of laser and pneumatic lithotripsy

OBJECTIVES

To study the treatment of ureteric stones by laser lithotripsy (LL) and pneumatic lithotripsy (PL), and to evaluate the results of the two treatment modalities to assess effectiveness, complications and cost benefits.

PATIENTS AND METHODS

Between January 1993 and February 1994 200 ureteric stones in 194 patients were fragmented intracorporeally, 48 by LL and 152 by PL. The ages of the patients ranged from 31 to 40 years with a male to female ratio of 2:1. All procedures were performed under general/regional anaesthetic in a day-care set-up. Patients were followed at weekly intervals. Re-treatment was carried out at 4 weeks where necessary.

RESULTS

The majority of the stones treated (84%) were in the lower third of the ureter, 69% measured 7-12 mm in diameter, and 61% were composed of calcium oxalate. Ninety-three per cent of the stones were fragmented in one treatment session. The overall stone-free status at 4 weeks was 95% for PL and 84% for LL. The non-fragmentation rate was 10% for LL and 1% for PL. Post-treatment complications were encountered in 8% of the patients treated by LL and 7% by PL.

CONCLUSIONS

Our experience shows that PL and LL both provide a safe and effective means of performing intracorporeal lithotripsy for smaller ureteric stones. However, PL is more effective in fragmenting larger and harder stones. Moreover, PL is more user-friendly and highly cost-effective compared with LL.

Comparison of 2 pulsed lasers for lithotripsy of ureteral calculi: report on 154 patients

Extracorporeal lithotripsy does not always provide satisfactory results for the treatment of ureteral stones. Such cases appear to be excellent indications for endocorporeal lithotripsy based on an association of ureteroscopy and laser. To compare the performances of 2 pulsed lasers, the pulsed dye laser (Candela) and solid Q switched laser (HMT), for the treatment of these calculi 161 ureteral stones were treated successively from November 1990 to March 1992 by a combination of ureteroscopy and laser. Endocorporeal lithotripsy was performed in 102 cases with the Candela laser, in 47 with the HMT laser and in 7 with both lasers. With a stable success rate greater than 90%, both lasers demonstrated equivalent performances regardless of the location of the stone along the ureter. However, while stone fragmentation was more rapid with the Candela laser, the HMT laser appeared to be more effective for dark stones (monohydrate calcium oxidate).

Anterograde endoscopic management of proximal ureteric stones

— The authors report on their experience gained in the percutaneous endoscopic treatment of 60 cases of stones in the upper ureter. The stones ranged in dimension from 12 to 15 mm. In 36 patients the push-back attempt was successful and after ultrasound crushing, the stones were removed percutaneously. After unsuccessful push-back in the other 24 patients, anterograde ureteroscopy was performed with crushing, using either Nd: YAG Pulsed Laser or electrohydraulic energy. Their experience shows that a combination of anterograde ureteroscopy and laser stone crushing is a reliable and efficient procedure for the treatment of impacted stones in the upper third of the ureter. In such cases laser crushing gives better results than the electrohydraulic procedure.

Comparison of holmium and flashlamp pumped dye lasers for use in lithotripsy of biliary calculi

The characteristics of laser lithotripsy of biliary calculi are compared for a flashlamp pumped dye laser (lambda = 640 nm) and a Cr:Tm:Ho-YAG laser (lambda = 2.1 microns). Data on fragmentation efficiency with respect to laser power and pulse repetition rate are presented for different types of stones. It is shown that both lasers can produce effective stone fragmentation. The laser power required for efficient fragmentation characteristics is significantly less for the visible wavelength laser. However, the problems associated with damage to the fiber tips of the delivery system during operation were found to be less with the near infrared wavelength. The laser power for efficient fragmentation with the dye laser varies significantly for different types of stones while the power for efficient fragmentation with the holmium laser is the same for all stones.

A special irrigation liquid to increase the reliability of laser-induced shockwave lithotripsy

For the laser-induced shockwave lithotripsy (LISL) the laser-pulses of a Q-switched Nd:YAG laser produce an optical breakdown in the irrigation liquid surrounding the urinary stone. Subsequently high-pressure shockwaves are emitted causing stone fragmentation. Since the LISL is an endoscopic technique, problems arise from the transmission of the laser pulses through optical fibers. The intensity threshold for an optical breakdown in commonly used saline solution amounts to 21 GW/cm2, in optical silica fibers, to about 3 GW/cm2. Therefore bare fibers cannot be used without being destroyed by a breakdown. So we have developed an irrigation liquid by adding small quantities of metal ions to saline solution to lower the threshold intensity. The most suitable ion was Fe3+ in a concentration of 0.02 mmol/l, which shows a lowering to 5 GW/cm2. In combination with a spherically shaped fiber exit the intensities that have to be transmitted are below the threshold of the fiber material. Using this irrigation liquid the overall reliability of the method could be significantly increased and several stone fragmentations can be performed with a single optical fiber.

Laser-induced shock wave lithotripsy. Influence of laser pulse energy and irrigation solutions on stone disintegration

With a high intensity Q-switched Nd-YAG laser shock waves can be generated in a liquid close to the calculus. Up to 80 mJ single pulse energy with 8 nsec pulse duration can be transmitted through flexible quartz fibers. Energy conversion and enhancement can be accomplished at the fiber tip with optical focussing of the light at the quartz tip, with irrigation solutions and with high pulse energies. Iron-III-dextran solutions (1 mg Fe3+/1) and magnesium chloride (50 mmol/l) increased the pressure in the laser induced breakdown up to ten times (8,000-10,000 bar). Smaller stone particles and higher efficacy in stone fragmentation could be achieved.