Laser-induced shockwave lithotripsy of gallstones

Laser-induced cavitation in plasmonic nanoparticle solutions: A comparative study between gold and titanium nitride

In this work, we present an extensive comparative study between novel titanium nitride nanoparticles (TiN NPs) and commercial gold nanorods (GNR), both dispersed in water and exposed to a pulsed laser-induced cavitation process. The optical density, shockwave emission, and bubble formation of these solutions were investigated using shadowgraphy, spatial transmittance modulation, and acoustic measurements. TiN nanoparticle solutions exhibited high stability undser a periodic nanosecond pulsed-laser irradiation, making these nanomaterials promising agents for high-power applications. In addition, they demonstrated a stronger nonlinear absorption compared to the GNR solutions, and plasma formation at lower laser energies. This study advances our understanding of the optical properties of TiN and discusses significant differences compared to gold, with important implications for future applications of this material in water treatment, nonlinear signal converting, and laser-induced cavitation for medical implementations, among others.

Choledochoscopy-assisted intraductal shock wave lithotripsy

In more than 90% of choledocholithiasis cases, endoscopic retrograde cholangiopancreatography with sphincterotomy and stone extraction are successful therapeutic options for clearance of the bile duct with the use of a stone retrieval balloon or basket. However, these techniques fail in a small percentage of patients with biliary stones, and advanced techniques for fragmentation must be used. Intraductal shock wave lithotripsy offers the endoscopist a therapeutic option that may be effective despite the difficulties of a large, impacted stone that cannot be captured by a basket, or a stricture that prohibits delivery of a stone beyond it. This article reviews the use of electrohydraulic lithotripsy and laser lithotripsy in the clinical setting.

Endoscopic laser lithotripsy for complicated bile duct stones: is cholangioscopic guidance necessary?

BACKGROUND

Endoscopic papillotomy is successful in more than 95% of the cases of choledocholithiasis. For patients with difficult bile duct stones not responding to mechanical lithotripsy, different methods for stone fragmentation have been developed.

AIM

To compare the results of laser lithotripsy with a stone-tissue recognizing system, when guided by fluoroscopy only or by cholangioscopy.

METHODS

Between 1992 and 2002 we have treated 89 patients with difficult bile duct stones by endoscopic retrograde cholangiopancreatography and laser lithotripsy. Unsuccessful extracorporeal shock-wave lithotripsy and electrohydraulic were also performed before laser in 35% and 26% of the cases, respectively.

RESULTS

Laser was effective in 79.2% of 72 patients guided by cholangioscopy and in 82.4% of 17 cases steered by fluoroscopy. The median number of impulses in the latter was 4,335 and 1,800 with the former technique. Two parameters influenced the manner of laser guidance. In cases of stones situated above a stricture, cholangioscopic control was more effective (64.7% vs. 31.9%). When the stones were in the distal bile duct, fluoroscopic control was more successful.

CONCLUSION

In cases of difficult stones in the distal bile duct, laser lithotripsy under fluoroscopic control is very effective and easily performed. Cholangioscopic guidance should be recommended just in cases of intrahepatic stones or in patients with stones situated proximal to a bile duct stenosis. In these cases, cholangioscopy should be performed either endoscopically or percutaneously.

Holmium-YAG laser for gall stone fragmentation: an endoscopic tool

A systematic review of the 2.1 mu holmium-YAG laser for gall stone lithotripsy was undertaken. This infrared laser, which can be used endoscopically and percutaneously, has safety advantages over other lasers and has potential as a general purpose vascular and surgical tool. Twenty nine gall stones (mean mass 1.3 g) were fragmented in vitro using pulse energies of 114 to 159 mJ/pulse at 5 Hz with a 0.6 mm fibre, while being held in an endoscopy basket. All stones were successfully fragmented, requiring an average of 566 pulses with a 5 Hz pulse repetition frequency. The number of pulses required increased with gall stone size and mass (p < 0.01), and decreased with both pulse energy (p < 0.01) and operator experience (p < 0.05). The biochemical content of the stone did not significantly affect the number of pulses needed. The potential hazard of the laser to the biliary endothelium was investigated. At the pulse energies used, five pulses at close contact penetrated into the serosa of fresh gall bladder wall. No damage was seen when two pulses were fired. This laser shows considerable promise in gall stone lithotripsy. Until further safety data are available, however, its use with endoscopic vision is advised.

Laser lithotripsy of difficult bile duct stones under direct visual control

Biliary laser lithotripsy was performed under direct visual control in 35 consecutive patients not amenable to routine endoscopy. The patients had 1-50 (median 1) bile duct stones with the greatest diameter of the largest stone being 9-42 mm (median 20 mm). Conventional endoscopic treatment had failed because of an inaccessible papilla (16 patients), biliary strictures (seven patients), and impaction or large size of calculi (12 patients). Twelve patients, depending on their anatomical condition, underwent peroral cholangioscopy by means of a mother-babyscope system. Percutaneous cholangioscopy was initially carried out in 23 patients, 7-20 days (median 10 days) after creation of a transhepatic fistula. Pulsed dye laser (32 patients) or alexandrite laser (three patients) lithotripsy was applied under an appropriate direct visual control in all cases. Complete stone disintegration succeeded in 33 of 35 patients. All resultant fragments passed the papilla within a mean number of 1.3 treatment sessions. Peroral cholangioscopic lithotripsy failed in two cases. One patient successfully underwent percutaneous laser treatment and the other patient was referred to surgery. Fever, temporary haemobilia, or a subcapsular liver haematoma were seen in a total of eight patients during establishment of the cutaneobiliary fistula. A 95 year old patient who had been admitted with septic cholangitis died because of cardiorespiratory failure 5 days after bile duct clearance. It is concluded that laser lithotripsy performed under a direct visual control is an effective and safe procedure for the non-surgical treatment of difficult bile duct stones. Ductal clearance can usually be achieved in a single treatment session when the papilla and the stones are accessible by the peroral route. Percutaneous cholangioscopic lithotripsy is more time consuming but highly effective even in patients with a difficult anatomy, bile duct strictures, or intrahepatic calculi. This approach should be limited, however, to cases not amenable to retrograde procedures because the creation of the cutaneobiliary fistula is not without risks.

New technologies and future applications of surgical lasers. The right tool for the right job

The real future of surgical lasers, and indeed of surgery itself, will depend on the integration of the surgeon into a system incorporating real-time tissue sensors, computer-directed robotic manipulation, and laser-tissue interactions that are customized to the clinical task. The human surgeon will operate as the central judgmental element in this mechanized and semiautomated laser surgical system. Only then will we really be able to make use of the subtle and varied laser-tissue effects now being discovered.

Biliary Laser Lithotripsy

Laser lithotripsy is an excellent method of fragmenting those biliary stones that cannot be removed easily by less technically advanced methods such as basket extraction. The energy can be delivered through fine flexible fibers, around 200 to 320 microns in diameter, that can be passed through the channels of a variety of small endoscopes. Currently, the optimal laser seems to a pulsed system because of the conversion of light to acoustic energy with minimal heating of the surrounding tissues, thus avoiding the chance of tissue injury and perforation. The best wavelength seems to be 504 nm, because at this wavelength, there is maximum absorption of laser energy by pigment stones, resulting in fragmentation using low-energy pulses. With further research, optimal wavelengths and pulse durations may emerge.

Lithotripsy of gallstones by means of a quality-switched giant-pulse neodymium:yttrium-aluminum-garnet laser. Basic in vitro studies using a highly flexible fiber system

The quality-switched neodymium:yttrium-aluminum-garnet laser represents a new instrument for athermal fragmentation of gallstones by transformation of optical energy into mechanical energy in the form of shock waves via local plasma formation. A highly flexible 300-micron fiber transmission system was used in basic investigations to determine the influence of varying pulse repetition rates (5-30 Hz) and pulse energies (15 and 20 mJ) on shock wave intensity and stone fragmentation in vitro for 105 biliary calculi of known size and chemical composition. After performance of 1200 shock wave pressure measurements using polyvinylidenefluoride hydrophones, stone fragmentation was analyzed by determination of fragment removal rates (volume of fragments removed per fragmentation time), ablation rates (mean volume removed per laser pulse), and median fragment sizes for each laser setting. With the quality-switched neodymium:yttrium-aluminum-garnet laser system, all concrements could be reliably disintegrated into small fragments (median diameter, 0.7-1.7 mm). Compared with pure cholesterol stones, a significantly higher fragment removal rate was achieved in cholesterol stones containing 30% calcium phosphate (P = 0.039), in cholesterol stones containing 20% pigment (P = 0.015), and in pure pigment stones (P = 0.007). Fragment removal rates, local shock wave pressures, and median grain sizes were significantly higher at a pulse energy of 20 mJ than with 15 mJ. Shock wave pressures showed a distinct dependence on pulse repetition rates at 20 mJ, yet not at 15 mJ. Because there is no evident hazard of thermal damage to tissue using the quality-switched neodymium:yttrium-aluminum-garnet laser, it appears to be a promising device for nonsurgical biliary stone therapy.

Endoscopic laser lithotripsy of large bile duct stones

Experimental work has established that the Candela (Candela Laser Corporation, Wayland, MA) flashlamp excited dye laser (wavelength, 504 nm) is a highly effective method for fragmenting biliary stones and has minimal potential for injuring the bile duct wall. This technique was evaluated in 25 complex patients whose stones, usually because of large size, did not respond to standard nonoperative treatment. The laser imaging was applied through a quartz fiber and aimed either under direct vision with choledochoscopes passed percutaneously or through a special "mother" duodenoscope or under fluoroscopic guidance at standard duodenoscopy. Laser treatment resulted in some fragmentation of stones in 23 cases. Subsequently, it proved that it was possible to clear the bile duct of stones in 20 patients, 12 of them receiving successful treatment during the same endoscopic procedure. There were no significant complications. This endoscopic technique seems to be a useful new alternative to surgery in patients with large and difficult bile duct stones.

Mechanical property studies of human gallstones

The recent development of gallstone fragmentation methods has increased the significance of the study of the mechanical properties of human gallstones. In the present work, fracture strength data and microhardness values of gallstones of various chemical compositions are presented as tested in both dry and simulated bile environments. Generally, both gallstone hardness and fracture strength values were significantly less than kidney stone values found in previous studies. However, a single calcium carbonate stone was found to have an outer shell hardness exceeding those values found for kidney stones. Diametral compression measurements in simulated bile conclusively demonstrated low gallstone fracture strength as well as brittle fracture in the stones tested. Based on the results of this study, one may conclude that the wide range of gallstone microhardnesses found may explain the reported difficulties previous investigators have experienced using various fragmentation techniques on specific gallstones. Moreover, gallstone mechanical properties may be relatively sensitive to bile-environment composition.

Removal of common bile duct stones by the combination of percutaneous balloon dilatation and extracorporeal shock-wave lithotripsy

Endoscopic papillotomy may not be possible in patients who have previously undergone gastric surgery. We describe the successful treatment of such a patient with ultrasound-guided, percutaneous transhepatic biliary drainage, followed by balloon dilatation of the sphincter of Oddi and extracorporeal shock-wave lithotripsy. Combinations of new treatment forms may be necessary and effective when single forms of treatment fail.

[Percutaneous transhepatic laser lithotripsy of gallstones--results of animal experiments]

Since laserinduced shock wave lithotripsy of gallstones is possible for treatment of common bile duct stones, the percutaneous transhepatic laserlithotripsy of stones in the gallbladder is examined in an animal study. In 8 animal experiments it could be shown that puncture of the gallbladder, dilatation of the working channel, (laserinduced) shock wave lithotripsy, removal of the fragments and the instruments are possible in one session. Neither when performing simple closure of the wound by suture nor by fibrinsealing severe side-effects could be recognized. After laserlithotripsy ablation of epithelium and hematomas can be observed, which are restituted within one month. The experiments show that in organ-saving shockwave lithotripsy there is no need for waiting for the development of a fistula and the percutaneous approach can be simplified.

Comparison of methods for transcatheter fragmentation of gallstones

Alternative methods have been considered for treating cholelithiasis. Compared to extracorporeal shockwave lithotripsy (ESWL), a percutaneous endoscopic approach would be more invasive, but would offer the advantage of immediate stone removal without the need for subsequent drug therapy. We performed an in vitro comparison of three methods of transcatheter cholecystolithotripsy with regard to effectiveness of stone fragmentation, damage to the gallbladder mucosa, and compatibility with percutaneous delivery systems. The three devices used for cholecystolithotripsy were the ultrasonic lithotriptor (UL), the electrohydraulic lithotriptor (EHL), and the thulium-holmium-chromium: YAG laser (THC:YAG). The UL effectively fragmented all types of stones studied, although it is necessary to hold the stone against the tip of the probe. The EHL quickly fragmented noncalcified and pigment stones simply by placing the tip in the vicinity of the stone, but calcified stones had to be held in position near the electrode. The THC:YAG was effective at fragmenting each type of stone, but the number of pulses required was quite large, corresponding to 7 min for some stones. The EHL had the most capacity for mucosal damage, followed by the THC:YAG laser. The UL produced no mucosal damage at the exposure times tested. The UL is not compatible with flexible endoscopes while the EHL and the THC:YAG are. Because of the specific advantages and disadvantages of each device, a combination of devices may be required for successful clinical cholecystolithotripsy.

Laserlithotripsy of common bile duct stones

Endoscopic retrograde laser lithotripsy of common bile duct stones is a new technique which can be carried out through the endoscope without anaesthesia using ordinary endoscopic equipment. In the method described here a flashlamp pulsed Neodymium YAG laser (wave length 1064 nm) was used. Light energy was transmitted along a highly flexible quartz fibre with a diameter of 0.2 mm. This new technique was used in nine patients with concrements in the common bile duct, which could not be removed with the established endoscopic techniques. In eight of the nine the concrements (maximum diameter 4.7 x 3.1 cm) could be fragmented and in six the fragments could be extracted from the common bile duct. The total energy required was 80-300 J; complications were not observed.

[Laser-induced shockwave lithotripsy--in vitro trial and animal experiment studies]

Laser induced shock wave lithotripsy is a new procedure to destroy gallstones. Stones of up to 500 mg are destroyed within 5 min. Severe reactions of the soft tissue cannot be observed in animal studies. No perforations, stenoses or thermic lesions after wound healing were observed. The development of an optomechanical transducer replacing the optical lens system at the end of the transmission guide allows its handling in flexible endoscopes. Clinical use is therefore possible from the technical aspect.

Endoscopic stenting for long-term treatment of large bile duct stones: 2- to 5-year follow-up

Seventeen elderly and high risk patients with large bile duct stones, who were treated by endoscopic insertion of a stent when attempts at stone extraction failed, are reported. In a follow-up of 2 to 5 years (median, 39 months), only two have so far required surgery for biliary sepsis and five have already died from other causes.