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Proceedings Paper

Loss of power output and laser fibre degradation during 120 watt lithium-triborate HPS laser vaporisation of the prostate
Author(s): Thomas Hermanns; Tullio Sulser; Lukas J. Hefermehl; Daniel Strebel; Maurice-Stephan Michel; Michael Müntener; Alexander H. Meier; Hans-Helge Seifert
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Paper Abstract

It has recently been shown that laser fibre deterioration leads to a significant decrease of power output during 80 W potassium titanyl phosphate (KTP) laser vaporisation (LV) of the prostate. This decrease results in inefficient vaporisation especially towards the end of the procedure. For the new 120 W lithium-triborate (LBO) High Performance System (HPS) laser not only higher power but also changes in beam characteristics and improved fibre quality have been advertised. However, high laser power has been identified as a risk factor for laser fibre degradation. Between July and September 2008 25 laser fibres were investigated during routine 120 W LBO-LV in 20 consecutive patients. Laser beam power was measured at baseline and after the application of every 25 kJ during the LV procedure. Postoperatively, the surgeon subjectively rated the performance of the respective fibre on a scale from 1 to 4 (1 indicating perfect and 4 insufficient performance). Additionally, microscopic examination of the fibre tip was performed. Median energy applied was 212 kJ. Changes of power output were similar for all fibres. Typically, a steep decrease of power output within the first 50 kJ was followed by a continuous mild decrease until the end of the procedure. After the application of 50 kJ the median power output was 63% (58-73% interquartile range) of the baseline value. The median power output at the end of the 275 kJ-lifespan of the fibres was 42% (40-47%). The median surgeons' rating of the overall performance of the laser fibres was 2 and the median estimated final decrease of power output 60%. Some degree of degradation at the emission window was microscopically detectable in all cases after the procedure. However, even after the application of 275 kJ, these structural changes were only moderate. Minor degradation of the laser fibre was associated with a significant decrease of power output during 120 W LBO-LV. However, following an early, steep decrease, power output remained relatively constant on a medium level for the rest of the fibre's lifespan. The subjective rating by the surgeons is in accordance with these findings. Improved properties of the LBO laser and enhanced fibre quality resulted in an only moderate decrease of power output which allowed for a consistently effective performance.

Paper Details

Date Published: 23 February 2009
PDF: 10 pages
Proc. SPIE 7161, Photonic Therapeutics and Diagnostics V, 71611I (23 February 2009); doi: 10.1117/12.809751
Show Author Affiliations
Thomas Hermanns, Univ. of Zürich, Univ. Hospital (Switzerland)
Tullio Sulser, Univ. of Zürich, Univ. Hospital (Switzerland)
Lukas J. Hefermehl, Univ. of Zürich, Univ. Hospital (Switzerland)
Daniel Strebel, Univ. of Zürich, Univ. Hospital (Switzerland)
Maurice-Stephan Michel, Univ. of Zürich, Univ. Hospital (Switzerland)
Mannheim Medical Ctr., Univ. of Heidelberg (Germany)
Michael Müntener, Univ. of Zürich, Univ. Hospital (Switzerland)
Alexander H. Meier, ETH Zürich (Switzerland)
Hans-Helge Seifert, Univ. of Zürich, Univ. Hospital (Switzerland)


Published in SPIE Proceedings Vol. 7161:
Photonic Therapeutics and Diagnostics V
Henry Hirschberg; Steen J. Madsen; Brian Jet-Fei Wong; Justus F. R. Ilgner; Kenton W. Gregory; Guillermo J. Tearney; Laura Marcu; Reza S. Malek; Nikiforos Kollias; Bernard Choi; Haishan Zeng, Editor(s)

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