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Proceedings Paper

Dynamic change of characteristics of (modified) fiber tips used with microsecond pulsed lasers in a liquid environment influencing the effectiveness and safety of treatment
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Paper Abstract

Microsecond pulsed laser systems, like the Thulium, Holmium and Erbium laser are being used for a broad range of medical applications in a liquid environment. Usually, the tissue ablation mechanism of these lasers is based on the instant formation of water vapor. When used with fiber delivery systems, the refraction of the beam coming out of the fiber will change the moment the liquid boundary turns to vapor. This dynamic change can be used in a controlled way but can also have adverse effects if not appreciated. In this study, the effect of the vapor phase change was investigated for various fiber shapes regarding optical and mechanical properties using high speed imaging and ray-trace simulation. Fiber tips of various shapes (bare, angled, tapered, ball shaped) were imaged with high-resolution using 1 &mgr;s light flashes in a video sequence of delay times from 1 to 2000 &mgr;s during exposure with pulsed 2.1 &mgr;m Holmium and pulsed 2.9 &mgr;m Erbium laser pulses. The tip was position in water or near a tissue surface. The dynamics of the explosive vapor bubble changed due to angle of refraction at the silica/vapor interface depending of the shape of the fiber tip. Ball shaped fibers form focused and highly divergent beams, angled fibers become side firing and tapered tips more concentrated. The observations are supported by ray-trace simulation. Clinically this mechanism can be used e.g. to create tiny side firing fibers in root channels of teeth. However, a damaged fiber tip may become unexpectedly side-firing resulting in adverse effects e.g. during lithotripsy. Ball-shaped fibers may be more resistant for damage due to impact with tissue. Using microsecond pulsed laser systems, the change in optical action of the fiber tip in liquid can influence the effectiveness and safety of the procedure.

Paper Details

Date Published: 7 February 2007
PDF: 8 pages
Proc. SPIE 6435, Optical Interactions with Tissue and Cells XVIII, 64350S (7 February 2007); doi: 10.1117/12.701233
Show Author Affiliations
Rudolf Verdaasdonk, Univ. Medical Ctr. Utrecht (Netherlands)
John Klaessens, Univ. Medical Ctr. Utrecht (Netherlands)
Rowland de Roode, Univ. Medical Ctr. Utrecht (Netherlands)
Tjeerd de Boorder, Univ. Medical Ctr. Utrecht (Netherlands)
Jan Blanken, Private Dental Clinic (Netherlands)

Published in SPIE Proceedings Vol. 6435:
Optical Interactions with Tissue and Cells XVIII
Steven L. Jacques; William P. Roach, Editor(s)

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