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Proceedings Paper

Interaction of laser radiation with tissue
Author(s): Heinz P. Weber; Adrian D. Zweig; Martin Frenz; Valerio Romano
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Paper Abstract

The iiin reason to use lasers for cutting tissue is the instant generation of a coagulated zone along the incision walls . This zone acts baertota however if it becone-s too thi it leads to undesired scar forxrtion durir the healing process. The thickness of the coagulated zone is strongly dependent on the details of the cutting rrecbanisrn that itself is determined by the laser and material pararreters. We studied the influence of laser penetration depth intensity and focal geoirtry as well as physical tissue properties on the resultir laser incisions . We iide our investigations on a ndel substance in as well as on freshly excis animal dermis . Laser pulses of 250 p. s duration and 4 Hz repetition rate were eniployed . We corrared incisions made with an laser at 2 . 94 imi to incisions from a laser. We studiI cutting for various focusing conditions . We found that often hydrodynaxnic instabilities developed within the crater and also learned how they can be avoided . The extensions of thermal damage zones depend much stronger on focusing geometry arid intensity than on the optical penetration depth of the cutting beam. Tissue material is eated liquefied and partially ejected during laser cutting. We show that the deree of thermal damage originates from the aimunt of hot material that is not ejected out of the crater of incision. Further we that tissue material is elastically displaced during laser cutting and recoils after cuttir back to exactly its initial position. In soft materials usually the incisions close at the upper end of the hole alnxst instantaneously after termination of the laser pulse . The vacancies left behind are filled with hot water vapor that condenses upon cooling leading to a strong suction process . Thus material from the surface can be pulled into the depth of the incision without being biologically deactivated. 1.

Paper Details

Date Published: 1 September 1990
PDF: 7 pages
Proc. SPIE 1353, First International Conference on Lasers and Medicine, (1 September 1990); doi: 10.1117/12.34933
Show Author Affiliations
Heinz P. Weber, Univ. of Berne (Switzerland)
Adrian D. Zweig, Univ. of Berne (Switzerland)
Martin Frenz, Univ. of Berne (Switzerland)
Valerio Romano, Univ. of Berne (Switzerland)


Published in SPIE Proceedings Vol. 1353:
First International Conference on Lasers and Medicine

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