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Proceedings Paper

Optimization of dosimetry and safety using the holmium laser for urology
Author(s): Christiaan F. P. van Swol; Rudolf M. Verdaasdonck; Bram Y. W. Zeijlemaker; Matthijs C. M. Grimbergen; Tom A. Boon
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Paper Abstract

The holmium laser has become accepted as a versatile instrument for urological applications, such as prostate resection, urethrotomy, tumor coagulation and lithotripsy. Presently, more powerful lasers have become available generating pulses up to 4 J at 80 W. The necessity of these high power systems in urology is ambiguous. In this study, the dosimetry as to efficacy and especially safety was investigated for various applications. The holmium laser ((lambda) equals 2.1 micrometer) emits its energy in 350 microsecond pulses which instantly turn water into vapor. Using high-speed photography explosive vapor bubbles with diameters over 10 mm were captured. The mechanical force of these bubbles, effectively fragments stones but may dilate and rupture a small lumen like the ureter. After implosion of the bubble, the energy of vaporization turns into heat. Depending on pulse energy and pulse repetition rate, tissue can be thermally affected up to 5 mm. For soft tissue applications, e.g., urethrotomy, prostatectomy or tumor coagulation, pulse energies of 0.5 - 1.5 J were applied at a high repetition rate (20 - 40 Hz) to provide sufficient coagulative and hemostatic effects. At higher pulse energies, the fiber tip was vibrating vigorously and the tissue was ripped to pieces decreasing hemostasis and visibility. For hard tissue applications, bursts of 0.5 J pulses at 5 Hz, proved to be sufficient to fragment all types of stones (including cystine) in the ureter and the bladder without mechanical or thermal damage to surrounding tissue. At higher settings, targeting the stone was less controlled and effective due to 'jumping' of the fiber tip with resulting mechanical and thermal trauma to the surrounding tissue. The holmium laser can be used effectively to coagulate and cut soft tissue and fragment stones at relatively low energy and power settings, thus minimizing the risk of complications.

Paper Details

Date Published: 1 July 1998
PDF: 7 pages
Proc. SPIE 3245, Lasers in Surgery: Advanced Characterization, Therapeutics, and Systems VIII, (1 July 1998); doi: 10.1117/12.312277
Show Author Affiliations
Christiaan F. P. van Swol, Univ. Hospital Utrecht (Netherlands)
Rudolf M. Verdaasdonck, Univ. Hospital Utrecht (Netherlands)
Bram Y. W. Zeijlemaker, Univ. Hospital Utrecht (Netherlands)
Matthijs C. M. Grimbergen, Univ. Hospital Utrecht (Netherlands)
Tom A. Boon, Univ. Hospital Utrecht (Netherlands)

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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