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Proceedings Paper

Laser lithotripsy with the Ho:YAG laser: fragmentation process revealed by time-resolved imaging
Author(s): Franz R. Schmidlin; Didier Beghuin; Guy P. Delacretaz; Giordano Venzi; Patrice Jichlinski; Klaus Rink; Hans-Juerg Leisinger; Peter Graber
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Paper Abstract

Improvements of endoscopic techniques have renewed the interest of urologists in laser lithotripsy in recent years. Laser energy can be easily transmitted through flexible fibers thereby enabling different surgical procedures such as cutting, coagulating and lithotripsy. The Ho:YAG laser offers multiple medical applications in Urology, among them stone fragmentation. However, the present knowledge of its fragmentation mechanism is incomplete. The objective was therefore to analyze the fragmentation process and to discuss the clinical implications related to the underlying fragmentation mechanism. The stone fragmentation process during Ho:YAG laser lithotripsy was observed by time resolved flash video imaging. Possible acoustic transient occurrence was simultaneously monitored with a PVDF-needle hydrophone. Fragmentation was performed on artificial and cystine kidney stones in water. We observed that though the fragmentation process is accompanied with the formation of a cavitation bubble, cavitation has only a minimal effect on stone fragmentation. Fragment ejection is mainly due to direct laser stone heating leading to vaporization of organic stone constituents and interstitial water. The minimal effect of the cavitation bubble is confirmed by acoustic transients measurements, which reveal weak pressure transients. Stone fragmentation with the Holmium laser is the result of vaporization of interstitial (stone) water and organic stone constituents. It is not due to the acoustic effects of a cavitation bubble or plasma formation. The fragmentation process is strongly related with heat production thereby harboring the risk of undesired thermal damage. Therefore, a solid comprehension of the fragmentation process is needed when using the different clinically available laser types of lithotripsy.

Paper Details

Date Published: 1 July 1998
PDF: 4 pages
Proc. SPIE 3245, Lasers in Surgery: Advanced Characterization, Therapeutics, and Systems VIII, (1 July 1998); doi: 10.1117/12.312324
Show Author Affiliations
Franz R. Schmidlin, Univ. Hospital Geneva (Switzerland)
Didier Beghuin, Ecole Polytechnique Federale de Lausanne (Belgium)
Guy P. Delacretaz, Ecole Polytechnique Federale de Lausanne (Switzerland)
Giordano Venzi, Univ. Hospital Geneva (Switzerland)
Patrice Jichlinski, Univ. Hospital Lausanne (Switzerland)
Klaus Rink, Ecole Polytechnique Federale de Lausanne (Switzerland)
Hans-Juerg Leisinger, Univ. Hospital Lausanne (Switzerland)
Peter Graber, Univ. Hospital Geneva (Switzerland)

Published in SPIE Proceedings Vol. 3245:
Lasers in Surgery: Advanced Characterization, Therapeutics, and Systems VIII
Graham M. Watson; Reza S. Malek; Aaron P. Perlmutter; Penny J. Smalley; Sharon L. Thomsen; Harvey Lui; Lawrence S. Bass; R. Rox Anderson; Lou Reinisch; C. Gaelyn Garrett; Kenneth Eugene Bartels; Lloyd P. Tate; R. Rox Anderson; Kenneth Eugene Bartels; Lawrence S. Bass; C. Gaelyn Garrett; Kenton W. Gregory; Harvey Lui; Reza S. Malek; Aaron P. Perlmutter; Lou Reinisch; Penny J. Smalley; Lloyd P. Tate; Sharon L. Thomsen; Graham M. Watson, Editor(s)

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