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Proceedings Paper

Comparison of different pulsed and Q-switched solid state laser systems for endoscopic laser-induced shockwave lithotripsy: performance and laser/stone interactions
Author(s): Erwin Steiger
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Paper Abstract

At present the laser induced shock wave lithotripsy (LISL) of urinary and biliary stones via fiber optic beam delivery is governed by two competing' laser systems: The flashlamp-pumped pulsed dye laser and the Q-switched Nd:YAG laser. The pulsed radiation of the dye system with pulse durations in the 1-2 .tsec region can be easily transmitted through extremely flexible fused silica fibers with core diameters of only 200 im whilst the Q-switched Nd:YAG laser with pulselengths of 5-25 nsec needs fibers with more than 400 tm core diameter. The dye laser releases acoustic shock waves for fragmentation simply by stone contact, the Q-switched Nd:YAG produces these waves in the surrounding aqueous medium by laser induced optical breakdown (LIB) when refocused by optical means or through additional metal absorbers, i.e. opto - mechanical couplers. We report on the system performances and laser/stone interactions of two alternative solid-state laser systems with variable pulselengths in the range of 1.7 - 30 sec and 30 - 1000 nsec, respectively: The pulsed psec-Nd:YAG laser and the Q-switched alexandrite laser. Regarding the endoscopic laser lithotripsy of urinary and biliary stones in the ureter or common bile duct, respectively, the laser energy delivery system, i.e. the optical fiber; is the most stressed part. Therefore we used long-pulse solid-state laser systems like the pulsed Nd:YAG laser with a pulse-slicing unit and a pulselength-tunable Q-switched alexandrite laser and studied fragmentation of synthetic plaster samples as well as urinary and biliary stones. The radiation of both laser systems can be effectively transmitted via standard 200 im core diameter optical quartz fibers what is absolutely necessary when used in conjunction with small caliber rigid or flexible endoscopes. As a compact and reliable solid-state system the alexandrite laser lithotripter is much less expensive than an extracorporeal shock wave lithotripter with the same fragmentation results and may become the laser of choice for LISL.

Paper Details

Date Published: 1 June 1990
PDF: 8 pages
Proc. SPIE 1200, Laser Surgery: Advanced Characterization, Therapeutics, and Systems II, (1 June 1990); doi: 10.1117/12.17445
Show Author Affiliations
Erwin Steiger, Carl Baasel Lasertechnik GmbH (Germany)

Published in SPIE Proceedings Vol. 1200:
Laser Surgery: Advanced Characterization, Therapeutics, and Systems II
Stephen N. Joffe M.D.; Kazuhiko Atsumi M.D., Editor(s)

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