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Proceedings Paper

Fragmentation methods in laser lithotripsy
Author(s): Zhi Xing Jiang; Colin Whitehurst; Terence A. King
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Paper Abstract

Following a series of opto-acoustic-mechanical and spectroscopic studies into the basic mechanisms of laser lithotripsy, a plasma-mediated opto-mechanical energy transfer model is presented. Laser energy, first absorbed by the calculi material at the surface and couples into the initiated plasma following ionization of vaporized material, is finally transformed into destructive mechanical energy via a shock wave induced by the impulsive expansion of the resulting plasma. This leads to the fragmentation of the calculi. The laser-plasma energy coupling gives a new definition for the fluence threshold to laser induced breakdown, which agrees with shock wave detection and analysis. A laser pulse shape with initial low intensity and sufficient fluence to vaporize a required amount of target material (lasting a few microsecond(s) ) and terminating in a short, intense pulse of about 1microsecond(s) or less, to couple most of the laser energy into the dense young plasma and so create high pressures, is required to produce optimum effect for laser lithotripsy. An opto-mechanical coupler has been designed which transfers the maximum laser energy into mechanically destructive energy, and successfully fragments various types of urinary and biliary calculi even including those calculi with poor surface absorptance, like pure white cystine. A solid state laser, Ho:YAG (2.1 micrometers wavelength and 150 microsecond(s) pulse width), has also been tested as an alternative to the flashlamp-excited dye laser. The underwater shock wave induced by this laser has been measured and has successfully fragmented calculi with poor absorptance in the visible region.

Paper Details

Date Published: 1 July 1991
PDF: 12 pages
Proc. SPIE 1421, Lasers in Urology, Laparoscopy, and General Surgery, (1 July 1991); doi: 10.1117/12.43913
Show Author Affiliations
Zhi Xing Jiang, Univ. of Manchester (United Kingdom)
Colin Whitehurst, Univ. of Manchester (United Kingdom)
Terence A. King, Univ. of Manchester (United Kingdom)

Published in SPIE Proceedings Vol. 1421:
Lasers in Urology, Laparoscopy, and General Surgery
Graham M. Watson M.D.; Rudolf W. Steiner; Joseph J. Pietrafitta M.D., Editor(s)

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