- Email: [email protected]
Gallstone Lithotripsy: In Vitro Comparison of Fragmentation with a Tunable-Dye Laser and an Ultrasonic Wire
Technical Developments and Instrumentation
Gallstone Lithotripsy: In Vitro Comparison of Fragmentation with a Tunable-DyeLaser and an Ultrasonic Wire1 Michael C. Soulen, MD Kevin L. Sullivan, MD Large bile duct stones require fragmentation prior to extraction through the papilla or through a percutaneous tract. This can be attempted with dissolution therapy, crushing baskets, or lithotripsy. Lithotripsy can be accomplished safely and effectively with tunabledye laser energy delivered through a flexible, 1-F optical fiber under endoscopic or fluoroscopic guidance, but laser technology is very costly. A prototype, flexible ball-tippedwire coupled to an ultrasonic generator via a piezoelectric crystal has been developed for sonolysis of atheroma and thrombus in humans. The purpose of this experiment was to compare human gallstone fragmentation in vitro with a tunable-dye laser and this prototype wire to see if the less expensive ultrasound device might provide an alternative to costly laser technology. Gallstones from 17 patients were subjected to lithotripsy in a water bath with each device until completely fragmented or 60 seconds had elapsed. Neither device effectively fragmented cholesterol stones under these conditions. The ultrasonic wire completely fragmented 57%of bilirubinate stones in 60 seconds. The tunable-dyelaser completely fragmented 100%of bilirubinate stones in less than 35 seconds ( P = .04). Tunable-dyelaser lithotripsy appears superior to the ultrasonic device for percutaneous treatment of bile duct stones.
CHoLEDOCHOLITHrASIS is an infrequent problem in patients after cholecystectomy. Retained stones in the immediate postoperative period can be removed through the mature T-tube tract (1). When T-tube access is not available, retrograde endoscopic extraction is usually successful (2).More recently, extracorporeal shock wave lithotripsy (ESWL) has been used to treat bile duct stones, but its exact role remains to be determined (3). Management by way of a transhepatic route is reserved for patients in whom these options are unsuccessful or contraindicated (4). Whether t h e approach is by means of retrograde endoscopy, a T-tube tract, or a transhepatic route, small stones can be removed with balloon catheters or baskets. Large stones must be reduced in size until small enough to pass through the papilla or through a percutaneous tract. This can be accomplished by dissolution therapy with monooctanoin or by fragmentation with baskets, ESWL, intracorporeal electrohydraulic lithotripsy (EHL), laser lithotripsy, or ultrasonic lithotripsy (5-12). The tunable-dye laser causes less tissue injury than neodynium: yttriumaluminum-garnet (Nd: YAG) lasers or EHL, because the wavelength of the coumarin dye is selectively absorbed by stone pigment and is poorly absorbed by tissue (6,13-15). All have been used clinically (8-12,161, with higher complication rates reported for EHL than for laser lithotripsy; however, the two techniques have not been formally compared in a prospective fashion, to our knowledge, and the previously reported complications of EHL may reflect the types of biliary access procedures used more than the lithotripsy devices employed. One advantage of the
'
Index terms: Bile ducts, calculi, 76.28 Bile ducts, stone extraction, 76.1228 Lithotripsy
JVIR 1992; 3:693-695
From the Division of CardiovascularIInterventional Radiology, Jefferson Medical College and Thomas Jefferson University Hospital, Philadelphia. Received January 15, 1992; revision requested March 4, revision received August 6, accepted August 7. Address reprint requests to M.C.S., AngiographylInterventional Radiology, Hospital of the University of Pennsylvania, 3400 Spruce St, Philadelphia, PA 19104. ' SCVIR, 1992
tunable-dye laser is that it does not necessarily require endoscopic guidance, while the Nd: YAG laser and EHL must be applied under direct vision to avoid tissue injury. The major disadvantage of the laser is its high cost, which limits its availability. Ultrasonic energy is an attractive modality, since experimentally it appears to preferentially fragment rigid materials such as calcified atheroma, while causing little or no injury to elastic structures such as vessel walls (17). Rigid ultrasonic lithotripsy devices have been used successfully in the gallbladder and kidney, but a flexible device is mandatory for intraductal applications and is currently not available for clinical use. Ultrasonic devices are also less expensive than laser technology by an order of magnitude. A number of devices that transmit ultrasonic energy down a flexible wire are under investigation for intravascular sonolysis of atheroma and thrombus (17-19). The purpose of this experiment was to compare the ability of a tunable-dye laser and a prototype ultrasonolytic wire to fragment human cholesterol and bilirubinate stones in vitro.
MATERIALS AND METHODS Several whole or large fragments of human gallstones were obtained from each of 17 cholecystectomy specimens. One stone or stone fragment from each patient was analyzed for chemical composition by a commercial company (Herring, Orlando, Fla). One or more pairs of stones of equal size were selected from each of the specimens, for a total of 12 pairs of cholesterol stones and seven pairs of bilirubin stones. One stone from each pair was treated with the laser, the other with the ultrasonic wire. Laser lithotripsy was performed with the Pulsolith tunable-dye laser (Technomed International, Danvers, Mass) using a 320-pm quartz fiber. The laser uses a coumarin dye, which produces a light beam with a wavelength of 504 nm. Eighty to 100 m J pulse energy was applied to the stones a t 5 Hz. These are the
694
Journal of Vascular and Interventional Radiology
November 1992
parameters used clinically for laser lithotripsy in humans. Laser lithotripsy was performed in a water bath with a customdesigned 12-F triple-lumen catheter (Microvasive, Watertown, Mass). One lumen accommodated the 320-km laser fiber, one provided irrigation, and the large central lumen allowed suction of stones to the catheter tip and clearance of fragments. The prototype ultrasound device (Sonic Needle, Farmingdale, NY), consists of a generator coupled via a piezoelectric crystal to a metal wire. The wire is mounted within a 6-F catheter, which is continuously irrigated with saline. The 50-W energy source causes oscillation of the wire tip at 20-30 kHz. Ultrasonic fragmentation was also performed in a water bath. The ultrasonic wire and catheter were placed coaxially through the suction lumen of a 16-F dual-lumen Tegtmeyer lithocentesis catheter (Medi-tech1Boston Scientific, Watertown, Mass), with the tip of the wire at the end of the catheter. Initial stone weights ranged from 20 to 1,290 mg. Since stones of similar sizes were selected from each patient to be tested with each device, there was no significant difference in initial weights of stones treated with the laser versus the ultrasonic wire (P = .2). Each stone was placed in the water bath and was drawn to the tip of the catheter with suction. Energy was applied until complete fragmentation occurred or 60 seconds had elapsed, whichever occurred first. In many cases the stone broke into two or more pieces, which were sucked in turn to the catheter tip and were fragmented. The time to complete fragmentation was recorded. In the absence of complete fragmentation, defined as reduction of the stone into particles small enough to be cleared by the suction lumen of the catheter, any residual stone was air-dried in a desiccator and weighed. Stone weights and rates of fragmentation (measured in milligrams per minute) for each device were compared with the paired t test. The ability of each device to achieve complete fragmentation was compared with the x2 test. -
-
RESULTS The mean fragmentation rates for all stones and for each subtype of stone (cholesterol or bilirubinate) are listed in Table 1. Bilirubinate stones fragmented signifi-
Table 1 Comparison of Fragmentation Rates Fragmentation Rate (mglmin) Tunable-Dye Ultrasonic Stone Type Laser Wire All 85 2 30 72 2 14 Cholesterol 37 2 18 67 2 16 Bilirubin 181 + 70 83 ? 27 Note.-Fragmentation rates are reported as mean r standard error.
Table 2 Comparison of Complete Fragmentation No. Stones Fragmented* Tunable-Dye Ultrasonic Stone Type Laser Wire All (n = 19) 10 (53) 8 (42) 5 (42) 4 (33) Cholesterol ( n = 12) Bilirubin (n = 7) 7 (100) 4 (57) * Numbers in parentheses are percentages.
cantly faster than cholesterol stones with either device (P = .001). Differences in fragmentation rates between the two de.05 vices were not significant at the P I level. There was a trend toward faster fragmentation of cholesterol stones with the ultrasonic wire (P = .21) and toward more rapid fragmentation of bilirubinate stones with the laser (P = ,151. Fragmentation rates are somewhat misleading in that they average together stones that were completely fragmented with those that were only partially broken up. Both devices tended to either break up the stones very rapidly (in 10-30 seconds) or just chip away at the surface, leaving most of the stone still intact at 60 seconds. Table 2 summarizes the data on complete fragmentation for each device and for each category of stone. The difference in the ability of the two devices to achieve complete fragmentation was significant only for bilirubinate stones (P = ,041.
DISCUSSION Neither the tunable-dye laser nor the ultrasonic wire effectively fragmented cholesterol stones under these test conditions. The proposed mechanism for ultrasonic lithotripsy is primarily mechanical
P Value .64 .21 .15
P Value .91 .82 .04
hammering by the rapidly oscillating wire tip, with possible secondary contributions from cavitation phenomena and acoustical streaming in the surrounding fluid medium. The ultrasonic device was more effective with bilirubinate stones than with cholesterol stones, probably because they tend to be softer and therefore more sensitive to mechanical disruption. In its present form, the ultrasonic wire appears inferior to laser systems currently in clinical use. In addition to its poorer fragmentation capability, the large size of the ultrasound system (6 F) compared with the laser fiber (1F) necessitates use of a larger percutaneous catheter to provide adequate irrigation and suction for fragment clearance. While large transhepatic tracts can be created safely if done slowly with time allowed for tract maturation, they have been associated with an increased incidence of bleeding complications (17);working through a smaller tract would be preferable both for the time saved and for any marginal safety benefit. The device is still undergoing development. It is possible that future refinements that improve energy transfer to the wire tip and exploration of different energies, frequencies of oscillation, and wire tip configurations may increase its clinical utility for lithotripsy. Similar devices have been applied successfully in the
Soulen and Sullivan
695
Volume 3 Number 4
vascular system for atherolysis (18). The laser completely fragmented 100% of bilirubinate stones in less than 35 seconds. The laser pulses create a plasma bubble at the surface of the stone. The shock wave and heat from the plasma cleave the stone. The dark pigmentation of the bilirubinate stones is thought to facilitate absorption of the laser energy, while the pale-colored cholesterol stones do this poorly. Altering the test conditions might affect our results. The experiment was performed in water, rather than in saline or bile. Previous experiments have shown that the type of fluid medium does not affect lithotripsy with the tunable-dye laser (19). This has not been proved for the ultrasonic wire; however, since the primary mechanism for ultrasonic lithotripsy is mechanical hammering, it seems unlikely that the nature of the surrounding fluid would have a major impact. Extending the contact time beyond 1minute might have increased the complete fragmentation rates, by allowing enough time to shatter some of the larger stones that were incompletely fragmented, although in general, stones either fractured rapidly or hardly at all. The 1-minute test period was sufficient to detect a difference in complete fragmentation rates for bilirubin stones between the two devices. The results of this experiment suggest that this prototype sonolytic wire is less effective a t fragmenting human gallstones than laser technology already in clinical use, under these test conditions.
References 1. Burhenne JH, Richards V, Mathewson C, Westdahl PR. Nonoperative extraction of retained biliary tract stones requiring
multiple sessions. Am J Surg 1974; 128: 288-292. Cotton PB. Endoscopic management of bile duct stones. Gut 1984; 25:587-597. Bland KI, Jones RS, Maher JW, et al. Extracorporeal shock-wave lithotripsy of bile duct calculi. Ann Surg 1989; 209:743755. Clouse ME, Stokes KR, Lee RGL, Falchuk KR. Bile duct stones: percutaneous transhepatic removal. Radiology 1986; 160:525-529. Palmer KR, Hofmann AF. Intraductal mono-octanoin for the direct dissolution of bile duct stones: experience in 343 patients. Gut 1986; 27:196-202. Ell C, Hochberger J , Muller D, et al. Laser lithotripsy of gallstones by means of a pulsed neodymium-YAG laser: in vitro and animal experiments. Endoscopy 1986; 18:92-94. Harrison J, Morris DL, Hatynes J , Hitchcock A, Womack C, Wherry DC. Electrohydraulic lithotripsy of gallstones: in vitro and animal studies. Gut 1987; 28:267271. Picus D, Weyman PJ, Marx MV. Role of percutaneous intracorporeal electrohydraulic lithotripsy in the treatment of biliary tract calculi. Radiology 1989; 170: 989-993. Berci G, Hamil JA, Grundfest W, Daykhovsky L, Paz-Partlow M. Percutaneous endoscopic laser lithotripsy of retained stones in the left hepatic duct. Surg Endosc 1990; 4:36-38. Feldman RK, Freeny PC, Kozarek RA. Pancreatic and biliary calculi: percutaneous treatment with tunable dye laser lithotripsy. Radiology 1990; 174:793-795. Flowers BF, Saslawsky MJ, Mathjers GL, Tonkin AK. Use of the pulsed dye laser and ultrasonic lithotripter for removal of multiple intrahepatic gallstones. Surg Gynecol Obstet 1990; 170:443-444. Cotton PB, Putnam WS, Weinerth J , et al. Endoscopic laser lithotripsy of large bile duct stones (abstr). Gastrointest Endosc 1989; 35:163.
13. Martin EC, Wolff M, Neff RA, Casarella WJ. Use of the electrohydraulic lithotriuter in the biliarv tree in dogs. - Radiology 1981; 139:215-217. 14. Nishioka NS, Kelsev PB. Kibbi A, Delmonico F, Parrish i ~Anderson , RR. Laser lithotripsy: animal studies of safety and efficacy. Lasers Med Surg 1988; 8: 357-362. 15. Lamont JS, Birkett DH, O'Deane JC, Babayan RK. Tissue effects of a pulsed dye laser and electrohydraulic lithotripsy on porcine urothelium (abstr). J Endourol ~ 1990: ~ ( S U D D1):S86. 16. ~osenscheinU, Bernstein J J , DiSegni E, Kaplinsky - E, Bernheim J, Rozensajn LA. Experimental ultrasonic angioplasiy: disruption of atherosclerotic plaques and thrombi in vitro and arterial recanalization in vivo. J Am Coll Cardiol 1990; 15: 711-717. 17. Mitchell SE, Shuman LS, Kaufman SL, et al. Biliary catheter drainage complicated by hemobilia: treatment by embolotherapy. Radiology 1985; 157:645-652. 18. Grether CM, Velez y Tello de M. M, Aguilar RJ, Borges J , Armilla M, Abundes A. Interventional US in peripheral arterial obstructive disease (abstr). Radiology 1990; 177(P):310. 19. Nishioka NS, Levins PC, Murray SC, Parrish JA, Anderson RR. Fragmentation of biliary calculi with tunable dye lasers. Gastroenterology 1987; 93:250-255.
Gallstone Lithotripsy: In Vitro Comparison of Fragmentation with a Tunable-DyeLaser and an Ultrasonic Wire1 Michael C. Soulen, MD Kevin L. Sullivan, MD Large bile duct stones require fragmentation prior to extraction through the papilla or through a percutaneous tract. This can be attempted with dissolution therapy, crushing baskets, or lithotripsy. Lithotripsy can be accomplished safely and effectively with tunabledye laser energy delivered through a flexible, 1-F optical fiber under endoscopic or fluoroscopic guidance, but laser technology is very costly. A prototype, flexible ball-tippedwire coupled to an ultrasonic generator via a piezoelectric crystal has been developed for sonolysis of atheroma and thrombus in humans. The purpose of this experiment was to compare human gallstone fragmentation in vitro with a tunable-dye laser and this prototype wire to see if the less expensive ultrasound device might provide an alternative to costly laser technology. Gallstones from 17 patients were subjected to lithotripsy in a water bath with each device until completely fragmented or 60 seconds had elapsed. Neither device effectively fragmented cholesterol stones under these conditions. The ultrasonic wire completely fragmented 57%of bilirubinate stones in 60 seconds. The tunable-dyelaser completely fragmented 100%of bilirubinate stones in less than 35 seconds ( P = .04). Tunable-dyelaser lithotripsy appears superior to the ultrasonic device for percutaneous treatment of bile duct stones.
CHoLEDOCHOLITHrASIS is an infrequent problem in patients after cholecystectomy. Retained stones in the immediate postoperative period can be removed through the mature T-tube tract (1). When T-tube access is not available, retrograde endoscopic extraction is usually successful (2).More recently, extracorporeal shock wave lithotripsy (ESWL) has been used to treat bile duct stones, but its exact role remains to be determined (3). Management by way of a transhepatic route is reserved for patients in whom these options are unsuccessful or contraindicated (4). Whether t h e approach is by means of retrograde endoscopy, a T-tube tract, or a transhepatic route, small stones can be removed with balloon catheters or baskets. Large stones must be reduced in size until small enough to pass through the papilla or through a percutaneous tract. This can be accomplished by dissolution therapy with monooctanoin or by fragmentation with baskets, ESWL, intracorporeal electrohydraulic lithotripsy (EHL), laser lithotripsy, or ultrasonic lithotripsy (5-12). The tunable-dye laser causes less tissue injury than neodynium: yttriumaluminum-garnet (Nd: YAG) lasers or EHL, because the wavelength of the coumarin dye is selectively absorbed by stone pigment and is poorly absorbed by tissue (6,13-15). All have been used clinically (8-12,161, with higher complication rates reported for EHL than for laser lithotripsy; however, the two techniques have not been formally compared in a prospective fashion, to our knowledge, and the previously reported complications of EHL may reflect the types of biliary access procedures used more than the lithotripsy devices employed. One advantage of the
'
Index terms: Bile ducts, calculi, 76.28 Bile ducts, stone extraction, 76.1228 Lithotripsy
JVIR 1992; 3:693-695
From the Division of CardiovascularIInterventional Radiology, Jefferson Medical College and Thomas Jefferson University Hospital, Philadelphia. Received January 15, 1992; revision requested March 4, revision received August 6, accepted August 7. Address reprint requests to M.C.S., AngiographylInterventional Radiology, Hospital of the University of Pennsylvania, 3400 Spruce St, Philadelphia, PA 19104. ' SCVIR, 1992
tunable-dye laser is that it does not necessarily require endoscopic guidance, while the Nd: YAG laser and EHL must be applied under direct vision to avoid tissue injury. The major disadvantage of the laser is its high cost, which limits its availability. Ultrasonic energy is an attractive modality, since experimentally it appears to preferentially fragment rigid materials such as calcified atheroma, while causing little or no injury to elastic structures such as vessel walls (17). Rigid ultrasonic lithotripsy devices have been used successfully in the gallbladder and kidney, but a flexible device is mandatory for intraductal applications and is currently not available for clinical use. Ultrasonic devices are also less expensive than laser technology by an order of magnitude. A number of devices that transmit ultrasonic energy down a flexible wire are under investigation for intravascular sonolysis of atheroma and thrombus (17-19). The purpose of this experiment was to compare the ability of a tunable-dye laser and a prototype ultrasonolytic wire to fragment human cholesterol and bilirubinate stones in vitro.
MATERIALS AND METHODS Several whole or large fragments of human gallstones were obtained from each of 17 cholecystectomy specimens. One stone or stone fragment from each patient was analyzed for chemical composition by a commercial company (Herring, Orlando, Fla). One or more pairs of stones of equal size were selected from each of the specimens, for a total of 12 pairs of cholesterol stones and seven pairs of bilirubin stones. One stone from each pair was treated with the laser, the other with the ultrasonic wire. Laser lithotripsy was performed with the Pulsolith tunable-dye laser (Technomed International, Danvers, Mass) using a 320-pm quartz fiber. The laser uses a coumarin dye, which produces a light beam with a wavelength of 504 nm. Eighty to 100 m J pulse energy was applied to the stones a t 5 Hz. These are the
694
Journal of Vascular and Interventional Radiology
November 1992
parameters used clinically for laser lithotripsy in humans. Laser lithotripsy was performed in a water bath with a customdesigned 12-F triple-lumen catheter (Microvasive, Watertown, Mass). One lumen accommodated the 320-km laser fiber, one provided irrigation, and the large central lumen allowed suction of stones to the catheter tip and clearance of fragments. The prototype ultrasound device (Sonic Needle, Farmingdale, NY), consists of a generator coupled via a piezoelectric crystal to a metal wire. The wire is mounted within a 6-F catheter, which is continuously irrigated with saline. The 50-W energy source causes oscillation of the wire tip at 20-30 kHz. Ultrasonic fragmentation was also performed in a water bath. The ultrasonic wire and catheter were placed coaxially through the suction lumen of a 16-F dual-lumen Tegtmeyer lithocentesis catheter (Medi-tech1Boston Scientific, Watertown, Mass), with the tip of the wire at the end of the catheter. Initial stone weights ranged from 20 to 1,290 mg. Since stones of similar sizes were selected from each patient to be tested with each device, there was no significant difference in initial weights of stones treated with the laser versus the ultrasonic wire (P = .2). Each stone was placed in the water bath and was drawn to the tip of the catheter with suction. Energy was applied until complete fragmentation occurred or 60 seconds had elapsed, whichever occurred first. In many cases the stone broke into two or more pieces, which were sucked in turn to the catheter tip and were fragmented. The time to complete fragmentation was recorded. In the absence of complete fragmentation, defined as reduction of the stone into particles small enough to be cleared by the suction lumen of the catheter, any residual stone was air-dried in a desiccator and weighed. Stone weights and rates of fragmentation (measured in milligrams per minute) for each device were compared with the paired t test. The ability of each device to achieve complete fragmentation was compared with the x2 test. -
-
RESULTS The mean fragmentation rates for all stones and for each subtype of stone (cholesterol or bilirubinate) are listed in Table 1. Bilirubinate stones fragmented signifi-
Table 1 Comparison of Fragmentation Rates Fragmentation Rate (mglmin) Tunable-Dye Ultrasonic Stone Type Laser Wire All 85 2 30 72 2 14 Cholesterol 37 2 18 67 2 16 Bilirubin 181 + 70 83 ? 27 Note.-Fragmentation rates are reported as mean r standard error.
Table 2 Comparison of Complete Fragmentation No. Stones Fragmented* Tunable-Dye Ultrasonic Stone Type Laser Wire All (n = 19) 10 (53) 8 (42) 5 (42) 4 (33) Cholesterol ( n = 12) Bilirubin (n = 7) 7 (100) 4 (57) * Numbers in parentheses are percentages.
cantly faster than cholesterol stones with either device (P = .001). Differences in fragmentation rates between the two de.05 vices were not significant at the P I level. There was a trend toward faster fragmentation of cholesterol stones with the ultrasonic wire (P = .21) and toward more rapid fragmentation of bilirubinate stones with the laser (P = ,151. Fragmentation rates are somewhat misleading in that they average together stones that were completely fragmented with those that were only partially broken up. Both devices tended to either break up the stones very rapidly (in 10-30 seconds) or just chip away at the surface, leaving most of the stone still intact at 60 seconds. Table 2 summarizes the data on complete fragmentation for each device and for each category of stone. The difference in the ability of the two devices to achieve complete fragmentation was significant only for bilirubinate stones (P = ,041.
DISCUSSION Neither the tunable-dye laser nor the ultrasonic wire effectively fragmented cholesterol stones under these test conditions. The proposed mechanism for ultrasonic lithotripsy is primarily mechanical
P Value .64 .21 .15
P Value .91 .82 .04
hammering by the rapidly oscillating wire tip, with possible secondary contributions from cavitation phenomena and acoustical streaming in the surrounding fluid medium. The ultrasonic device was more effective with bilirubinate stones than with cholesterol stones, probably because they tend to be softer and therefore more sensitive to mechanical disruption. In its present form, the ultrasonic wire appears inferior to laser systems currently in clinical use. In addition to its poorer fragmentation capability, the large size of the ultrasound system (6 F) compared with the laser fiber (1F) necessitates use of a larger percutaneous catheter to provide adequate irrigation and suction for fragment clearance. While large transhepatic tracts can be created safely if done slowly with time allowed for tract maturation, they have been associated with an increased incidence of bleeding complications (17);working through a smaller tract would be preferable both for the time saved and for any marginal safety benefit. The device is still undergoing development. It is possible that future refinements that improve energy transfer to the wire tip and exploration of different energies, frequencies of oscillation, and wire tip configurations may increase its clinical utility for lithotripsy. Similar devices have been applied successfully in the
Soulen and Sullivan
695
Volume 3 Number 4
vascular system for atherolysis (18). The laser completely fragmented 100% of bilirubinate stones in less than 35 seconds. The laser pulses create a plasma bubble at the surface of the stone. The shock wave and heat from the plasma cleave the stone. The dark pigmentation of the bilirubinate stones is thought to facilitate absorption of the laser energy, while the pale-colored cholesterol stones do this poorly. Altering the test conditions might affect our results. The experiment was performed in water, rather than in saline or bile. Previous experiments have shown that the type of fluid medium does not affect lithotripsy with the tunable-dye laser (19). This has not been proved for the ultrasonic wire; however, since the primary mechanism for ultrasonic lithotripsy is mechanical hammering, it seems unlikely that the nature of the surrounding fluid would have a major impact. Extending the contact time beyond 1minute might have increased the complete fragmentation rates, by allowing enough time to shatter some of the larger stones that were incompletely fragmented, although in general, stones either fractured rapidly or hardly at all. The 1-minute test period was sufficient to detect a difference in complete fragmentation rates for bilirubin stones between the two devices. The results of this experiment suggest that this prototype sonolytic wire is less effective a t fragmenting human gallstones than laser technology already in clinical use, under these test conditions.
References 1. Burhenne JH, Richards V, Mathewson C, Westdahl PR. Nonoperative extraction of retained biliary tract stones requiring
multiple sessions. Am J Surg 1974; 128: 288-292. Cotton PB. Endoscopic management of bile duct stones. Gut 1984; 25:587-597. Bland KI, Jones RS, Maher JW, et al. Extracorporeal shock-wave lithotripsy of bile duct calculi. Ann Surg 1989; 209:743755. Clouse ME, Stokes KR, Lee RGL, Falchuk KR. Bile duct stones: percutaneous transhepatic removal. Radiology 1986; 160:525-529. Palmer KR, Hofmann AF. Intraductal mono-octanoin for the direct dissolution of bile duct stones: experience in 343 patients. Gut 1986; 27:196-202. Ell C, Hochberger J , Muller D, et al. Laser lithotripsy of gallstones by means of a pulsed neodymium-YAG laser: in vitro and animal experiments. Endoscopy 1986; 18:92-94. Harrison J, Morris DL, Hatynes J , Hitchcock A, Womack C, Wherry DC. Electrohydraulic lithotripsy of gallstones: in vitro and animal studies. Gut 1987; 28:267271. Picus D, Weyman PJ, Marx MV. Role of percutaneous intracorporeal electrohydraulic lithotripsy in the treatment of biliary tract calculi. Radiology 1989; 170: 989-993. Berci G, Hamil JA, Grundfest W, Daykhovsky L, Paz-Partlow M. Percutaneous endoscopic laser lithotripsy of retained stones in the left hepatic duct. Surg Endosc 1990; 4:36-38. Feldman RK, Freeny PC, Kozarek RA. Pancreatic and biliary calculi: percutaneous treatment with tunable dye laser lithotripsy. Radiology 1990; 174:793-795. Flowers BF, Saslawsky MJ, Mathjers GL, Tonkin AK. Use of the pulsed dye laser and ultrasonic lithotripter for removal of multiple intrahepatic gallstones. Surg Gynecol Obstet 1990; 170:443-444. Cotton PB, Putnam WS, Weinerth J , et al. Endoscopic laser lithotripsy of large bile duct stones (abstr). Gastrointest Endosc 1989; 35:163.
13. Martin EC, Wolff M, Neff RA, Casarella WJ. Use of the electrohydraulic lithotriuter in the biliarv tree in dogs. - Radiology 1981; 139:215-217. 14. Nishioka NS, Kelsev PB. Kibbi A, Delmonico F, Parrish i ~Anderson , RR. Laser lithotripsy: animal studies of safety and efficacy. Lasers Med Surg 1988; 8: 357-362. 15. Lamont JS, Birkett DH, O'Deane JC, Babayan RK. Tissue effects of a pulsed dye laser and electrohydraulic lithotripsy on porcine urothelium (abstr). J Endourol ~ 1990: ~ ( S U D D1):S86. 16. ~osenscheinU, Bernstein J J , DiSegni E, Kaplinsky - E, Bernheim J, Rozensajn LA. Experimental ultrasonic angioplasiy: disruption of atherosclerotic plaques and thrombi in vitro and arterial recanalization in vivo. J Am Coll Cardiol 1990; 15: 711-717. 17. Mitchell SE, Shuman LS, Kaufman SL, et al. Biliary catheter drainage complicated by hemobilia: treatment by embolotherapy. Radiology 1985; 157:645-652. 18. Grether CM, Velez y Tello de M. M, Aguilar RJ, Borges J , Armilla M, Abundes A. Interventional US in peripheral arterial obstructive disease (abstr). Radiology 1990; 177(P):310. 19. Nishioka NS, Levins PC, Murray SC, Parrish JA, Anderson RR. Fragmentation of biliary calculi with tunable dye lasers. Gastroenterology 1987; 93:250-255.