Shock Wave Lithotripter Research Articles

Power Difference in Spectrum of Sound Radiation before and after Break of Phantom by Piezoelectric Extracorporeal Shock Wave Lithotriptor

This paper investigates the difference in the spectrum of sound radiated before and after the break of a phantom at a focal point of the piezoelectric extracorporeal shock wave lithotriptor (ESWL) in order to identify the break time or to examine whether a calculus exists exactly at the focal point or not. From the preliminary experiments using a piece of chalk as a phantom of a calculus to measure the sound radiated when impact is applied to the chalk by an impact hammer, it is found that the bending vibration component of the vibration is exhibited in the spectrum of sound. However, for small-sized chalk shorter than 3 cm, the peak frequency of the bending vibration is higher than 20 kHz. From the experiments using a piezoeletric ESWL, it is found that there is clear difference in the power spectra among the sound radiated before the break, that radiated just after the break in the breaking process, and that radiated when the chalk does not exist at the focal point of the ESWL. These characteristics will be effective for the examination of the existence of the calculus at the focal point.

The spatial distribution of cavitation induced acoustic emission, sonoluminescence and cell lysis in the field of a shock wave lithotripter

This study examines the spatial distribution of various properties attributed to the cavitation field generated by a shock wave lithotripter. These properties include acoustic emission and sonoluminescence, which result from violent bubble collapse, and the degree of cell lysis in vitro, which appears to be related to cavitation. The acoustic emission detected with a 1 MHz, 12 cm diameter focused hydrophone occurs in two distinct bursts. The immediate signal is emitted from a small region contained within the 4 MPa peak negative pressure contour. A second, delayed, burst is emitted from a region extending further along the beam axis. The delay between these two bursts has also been mapped, and the longest delay occurs at positions close to the regions of maximum peak negative pressure. Sonoluminescence from both single and multiple shocks occurs in a broader region than the acoustic emission but the measurement technique does not allow time resolution of the signal. Cell lysis occurs in a relatively small region that correlates closely with the immediate acoustic emission for a shock propagating in a gelatine solution.

The influence of fluid properties and pulse amplitude on bubble dynamics in the field of a shock wave lithotripter

This study concerns the radial dynamics of a bubble driven by pulsed ultrasound of the type generated during extracorporeal shock wave lithotripsy. In particular, a numerical model has been used to examine the sensitivity of the bubble oscillations to changes in both the amplitude of the driving field and the physical conditions of the fluid surrounding the bubble: viscosity, surface tension, temperature and gas content. It is shown that, at high negative pressures (p-=10 MPa) as in lithotripsy, the timing and amplitude of bubble collapses have a considerably reduced sensitivity to the initial bubble size and all fluid parameters, except gas content, compared with those expected in lower-amplitude fields (p-=0.2 MPa). This study indicates that, in the lithotripsy fields, the differences in the viscosity, surface tension and temperature of body fluids and the initial bubble size will have little effect on bubble dynamics compared with those expected in water.

Extracorporeal Shock Wave Lithotripsy for Bladder Stones

Between December 1989 and July 1991, 29 patients with bladder stones were treated on the MPL 9000 extracorporeal shock wave lithotriptor using ultrasound for localisation. The mean stone dimensions were 22.65 x 15.17 mm (< 400 mm2 in 20 patients); 75% of patients required only 1 ESWL session but the largest stone (2025 mm2) required 3. Whilst larger stones tended to require more shock waves, linear regression analysis showed a poor fit and factors other than size (operator experience and stone hardness) may determine the number of shock waves required. Satisfactory fragmentation was obtained in all patients. All were treated under intravenous analgesia without anaesthesia. Three patients also had outflow obstruction and were treated by transurethral resection of the prostate (TURP) on the day after completing ESWL. ESWL prior to TURP reduces the morbidity and operating time associated with endoscopic therapy of bladder stones. Macroscopic fragments remaining after ESWL can be washed out at TURP.

Interaction of lithotripter-generated shock waves with air bubbles

The shock wave-induced collapse and jet formation of pre-existing air bubbles at the focus of an extracorporeal shock wave lithotripter is investigated using high-speed photography. The experimentally obtained collapse time, ranging from 1 to 9 μs for bubbles with an initial radius R0 of 0.15 to 1.2 mm, agrees well with numerical results obtained using the Gilmore model. The collapse time is not linearly dependent on the initial bubble diameter since the temporal profile of the lithotripter wave contains a stress wave. The bubbles, positioned below a thin plastic foil, show strong jet formation in the direction of wave propagation with peak velocities of up to 770 m/s at the moment of collapse. Bubbles of initial radii between 0.3 and 0.7 mm always induce perforation of the foil by the jet (hole diameter 80–300 μm). Averaging the jet flow speed over 5 μs immediately after the collapse results in velocities from nearly zero up to 210 m/s, depending on the initial bubble size, with a maximum at R0=550 μm. This maximum is related to the temporal profile of the shock wave and to the effective cross section of the bubble for shock wave energy transfer. As cavitation bubbles are generated in the focal region of the lithotripter, the results are discussed with respect to the processes in a cavitation bubble field, which are of importance in cavitation erosion as well as in extracorporeal shock wave lithotripsy.

Measurements of Pressure of Extracorporeal Shock Wave Lithotripter Using Pressure-Sensitive Papers

This paper describes measurements of pressures at the focal region of the extracorporeal shock wave lithotripter (ESWL) using pressure-sensitive papers. At the focal region of ESWL, ordinary hydrophones are quickly damaged, because of very high pressures. Recently, measurements of pressure at the focal region of ESWL using pressure-sensitive paper have been advised. Therefore, we have studied the effectiveness of pressure-sensitive papers in the measurement of high acoustic pressures at the focal region of ESWL.

Pressure Distribution for Piezoelectric Extracorporeal Shock Wave Lithotripsy

The objective of this study is to develop a safer and more effective extracorporeal shock wave lithotripter. The first stage of the study shows the sound pressure field of the shock wave made by an ECHOLITH ESL-500A. The sound pressure distribution is in a ring configuration on a 60 mm plane in front of the focal plane. As the plane approaches the focal plane, the sound pressure relatively increases at the cross point with the axis of the transducer and decreases at the ring. The focal zone is 2.5 mm×16.1 mm at 60 V driving voltage and 1.8 mm×14.2 mm at “INTENSITY 2.” In the next stage we propose a method for changing the field by electronic driving control of each piezoceramic element for effective therapy. The focal zone can be changed from 3.1 mm×19.1 mm to 3.9 mm×32.4 mm at 60 V driving voltage with this method. These focal zones are calculated by means of computer simulation.

Variation of Pressure Waveforms in Measurements of Extracorporeal Shock Wave Lithotripter

In this paper, we describe measurement of variation in pressure waveforms of the acoustic field of an extra-corporeal shock-wave lithotripter (ESWL). Variations in the measured acoustic fields and pressure waveform of an underwater spark-gap-type ESWL with an exhausted spark plug electrode have been reported by researchers using crystal sensors. If the ESWL spark plugs become exhausted, patients feel pain during kidney, biliary stone disintegration. We studied the relationship between exhaustion of electrodes and the variation of pressure waveforms and shock-wave fields of the ESWL using a newly developed hydrophone.

Lithotripter shock wave propagation through layered media

Recent advances in the computation of shock wave front propagation [P. T. Christopher and K. J. Parker, J. Acoust. Soc. Am. 90, 488–499 (1991)] have allowed the prediction of spark-gap lithotripter waveforms both on and off-axis for a variety of geometries and conditions. Since in both urinary and biliary lithotripsy, shock pulses must propagate through layered human tissues (e.g., fat, muscle, and other soft tissues) it is especially important to understand how waveforms evolve in layered media. Comparisons of computational predictions and experimental results are presented for a laboratory lithotripter of our own construction whose axis of symmetry is vertical. Measurements of waveforms were made using a novel PVDF membrane hydrophone [E. C. Everbach, J. Acoust. Soc. Am. Suppl. 1 87, S128 (1990)] immersed in oil–water layers horizontally stratified by buoyancy forces. The comparisons show sufficient agreement to allow the possibility of optimizing lithotripter reflector geometries so that waveforms could be tailored to accommodate tissue configurations of individual patients.

Experience with the Direx Tripter X-1 shock-wave lithotripter.

The authors give account of the experience they gained with the Direx Tripter X-1 (ESWL) apparatus. In a random material they succeeded to render 81.5% of the patients stone free within three months. They judge the apparatus suitable for in situ treatment of pelvic and ureteric stones and for the monotherapy of staghorn calculi. It is easy to handle, inexpensive to buy and maintain but noisy to operate, moreover the patient has to be anaesthetized. All in all it is highly useful in the treatment of renal lithiasis.

Anesthesia and Complications of Extracorporeal Shock Wave Lithotripsy of Urinary Calculi

The techniques of anesthesia for extracorporeal shock wave lithotripsy of urinary calculi and the associated complications in 600 treatments with the second generation lithotriptor Siemens Lithostar were studied. General anesthesia was used in 17 treatments (2.8%) and epidural anesthesia was applied in 73 (12%), primarily in children and patients in need of simultaneous surgical auxiliary procedures. A total of 510 treatments (85%) was performed with a combination of local infiltration anesthesia and supplementary intravenous opiates. In 65% of the cases only 2 injections of opiates were sufficient for pain relief. There were no complications in 394 treatments (77%) and minor complications, such as arrhythmia (9.2%) and nausea/vomiting (7.6%), were easily treated. Respiratory depression was observed in 10 cases (2%) and this potentially dangerous complication was associated with simultaneous administration of opiates and midazolam. Only 9 treatments (1.8%) had to be terminated due to complications. It is concluded that most treatments of urinary calculi with this second generation extracorporeal shock wave lithotriptor can be performed with local infiltration anesthesia combined with supplementary short-acting opiates intravenously for pain relief and sedation. When administering supplementary midazolam for sedation the risk of respiratory depression should be considered.

Clinical Trials of the Northgate SD-3 Dual-Purpose Lithotriptor for Renal Calculi

The Northgate SD-3 is a bathless, portable shock wave lithotriptor made in the United States. It uses ultrasound localization and spark-gap, electrode-generated shock waves to fragment calculi in the upper urinary tract. Since October 1987, 312 treatments have been performed on 281 patients (286 kidneys) with stone burdens less than 2cm. during clinical trials at 6 investigational sites in the United States. A fragmentation rate of 94% was achieved. Of the treatments 78% were judged successful (stone-free or fragments of less than 5mm. remaining in an asymptomatic patient) and a 3-month stone-free rate of 58% was noted. The retreatment rate was 9% and the ancillary procedure rate was 5%. The complications (hematuria, ecchymosis, pain, obstruction) were mild and not unlike those seen in patients undergoing lithotripsy with other devices.

In situ prone ESWL for the treatment of lower ureteral stones: experience with 28 patients.

Twenty-eight patients with lower ureteral stones underwent in situ extracorporeal shock wave lithotripsy (ESWL) in the prone position over the period of 7 months between March 1990 and September 1990. For stone disintegration the spark gap shock wave lithotripter Tripter XI (Direx) was used. Satisfactory disintegration was achieved in 93 per cent of patients. The stone-free rate at 12 weeks was 82 per cent, and 11 per cent had residual fragments less than or equal to 4 mm in diameter. Twenty-one per cent of patients required repeat treatments. For only 2 patients general anaesthesia was required (7 per cent). There were no remarkable complications except for haemospermia which resolved spontaneously 15 days after treatment. It was concluded that in situ prone ESWL is an effective and safe procedure for the treatment of lower ureteral stones.

Transient increase in membrane permeability of L1210 cells upon exposure to lithotripter shock waves in vitro.

Transient increase in membrane permeability of L1210 cells upon exposure to lithotripter shock waves in vitro.

In vitro interaction of lithotripter shock waves and cytotoxic drugs.

The effect of a combination of lithotripter shock waves and cytotoxic drugs was examined in vitro. L1210 cells in suspension were exposed to shock waves during incubation with cislatin, doxorubicin, daunorubicin, THP-doxorubicin, or aclacinomycin. Proliferation was determined using the 3-4,5 dimethylthiazol-2,5 diphenyl tetrazolium bromide assay. Dose enhancement ratios were calculated for each drug in order to determine the effect of the additional exposure to shock waves. In addition, partition coefficients and IC50s of the drugs were determined. It was found, that the dose enhancement ratios increased for the drugs with decreasing cytotoxicity. The effect of all five drugs was enhanced by shock waves to a higher degree at 7 min incubation as compared to 50 min incubation. The effect of cisplatin was most significantly enhanced, with a dose enhancement ratio of 6.7 at 7 min incubation. The enhancement increased with the operating voltage used for generating the shock waves, and was only present when cells were exposed to shock waves during the incubation with the drug. An increase in cellular membrane permeability is proposed as the mechanism of interaction between shock waves and drugs.

The effect of isolated high-energy shock wave treatments on subsequent bacterial growth.

To determine whether high-energy shock waves possess bactericidal potential, ATCC strains of Escherichia coli, Streptococcus faecalis, Pseudomonas aeruginosa and Staphylococcus aureus were suspended in solution at concentrations approximating 10(6) bacteria per milliliter, placed in polypropylene cryovials, and immersed in the water bath of a Dornier HM3 lithotriptor. Each cryovial was then fluoroscopically guided to the epicenter of the f2 focal point and 2000 shocks at 20 kV applied. Suspensions were then serially diluted and colony counts obtained. The procedure was then repeated with 4000 shocks at 20 kV from the Dornier HM3 and 4000 shocks at intensity level 4 from a Wolff Piezolith 2200 shock wave lithotriptor. Comparison of shock-wave-treated and sham-treated bacterial suspensions revealed no significant difference in bacterial growth according to the colony count technique. We conclude that high-energy shock waves, whether generated by spark gap or piezoelectric array, do not possess significant bactericidal activity.

Acoustic emission and sonoluminescence due to cavitation at the beam focus of an electrohydraulic shock wave lithotripter.

The acoustic emission from cavitation in the field of an extracorporeal shock wave lithotripter has been studied using a lead zirconate titanate piezoceramic (PC4) hydrophone in the form of a 100-mm diameter focused bowl of 120-mm focal length. With this hydrophone directed at the beam focus of an electrohydraulic lithotripter radiating into water, it is possible to identify signals well above the noise level, at the 1-MHz resonance of the hydrophone, which originate at the beam focus. Light emission, attributed to sonoluminescence, is also shown to originate at the focal region of the lithotripter, and the signal obtained from a fast photomultiplier tube directed at the focus has similarities in structure and timing to the detected acoustic signals. The multiple shock emission resulting from a single discharge of an electrohydraulic source is shown to result in two separate bursts of cavitational activity separated by a period of 3-4 ms. The signal burst corresponding to the primary shock has a duration of about 600 microseconds with little noticeable structure. The signal burst associated with the secondary shock has a reproducible structure with two distinct peaks separated by about 200 microseconds depending on the shock amplitude. THe timing and structure of each burst is shown to be in reasonable agreement with the theoretical predictions made by Church (1989) based on the Gilmore model of bubble dynamics. In particular, it is shown that it is possible to obtain precise measurements of the time delay between the separate peaks within the signal burst detected following the secondary shock and this may, as predicted, provide a method of determining the size of bubbles remaining after the primary shock.

In situ extracorporeal shock wave lithotripsy for upper ureteral stones: experience with 65 patients.

A total of 65 patients with 67 upper ureteral stones underwent in situ extracorporeal shock wave lithotripsy (ESWL) between March 1990 and September 1990. For stone disintegration the electrohydraulic shock wave lithotripter Tripter XI (Direx) was used. Eighty-seven per cent of stones showed satisfactory disintegration after the first treatment and a further 9 per cent after repeat treatments. The stone-free rate at 12 weeks was 85 per cent. General anaesthesia was needed in only 12 per cent of patients. The retreatment rate was 13 per cent. It was concluded that in situ ESWL is an effective procedure with negligible morbidity for treating upper ureteral stones.

Influence of dissolved and free gases on iodine release and cell killing by shock waves in vitro

Exposure of a potassium iodide solution to lithotripter shock waves resulted in formation of iodine with the amount of iodine depending on the gas dissolved in the solution. Iodine yield was higher with O 2 and Ar, as compared to CO 2 and N 2O; degassed solution revealed the lowest iodine yield. Exposure of L1210 mouse leukemia cells to shock waves reduced the number of viable cells with no difference between O 2-, Ar-, or N 2O-equilibrated and degassed conditions. CO 2 equilibration resulted in a more pronounced reduction. The difference between chemical and biological effects argues against the involvement of free radicals in cell killing by shock waves. In additional experiments, gas bubbles of various sizes were introduced into the test vials. Addition of a 10 μL gas bubble revealed an over 10-fold increase in iodine yield from degassed potassium iodide solution with all gases. Addition of a gas bubble also reduced the number of viable cells again with no difference between the gases. It is suggested that shock wave-gas bubble interaction is an important mediator of iodine release and cell killing by shock waves.

Endoscopic Management of Difficult Bile Duct Stones

More than 90% of all common bile duct concrements can be removed via the endoscopic retrograde route via endoscopic sphincterotomy, stone extraction by baskets and balloon catheters, or mechanical lithotripsy. Oversized, very hard or impacted stones, however, often still resist conventional endoscopic therapy. Promising new or improved approaches for the treatment of these stones are intracorporeal or extracorporeal shock wave lithotripsy. Shockwave lithotriptors for extracorporeal shockwave lithotripsy are currently available worldwide. However, for the waterbath first generation devices, general anesthesia is required since shockwaves are very painful. Furthermore, an x-ray localization system is essential to visualize the stones after having filled the bile duct over a nasobiliary catheter. An average of two shockwave treatments with additional two to four endoscopic sessions are required. ln tracorporeal lithotripsy promises more comfort and less effort for the patient. Shockwaves are generated either by means of the spark gap principle (electrohydraulic probes) or by laser-induced plasma generation. Laser-induced shockwave lithotripsy appears to be more safer, since with dye and solid state lasers, athermal, well-controlled shockwaves can be generateJ without the risks for duct perfo ration (as described for the electrohydraulic system). Furthermore, a recently developed stone-tissue detection system integrated in a new dye laser system enchances the safety of laser-induced lithotripsy. ln consequence, lithotripsy without direct endoscopic control appears possible in selected cases.