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Proceedings Paper

Damage to microvessels during pused laser treatment of port-wine stains
Author(s): Lars Othar Svaasand; Elisanne Janne Fiskerstrand; Lill Tove Norvang Nilsen; E. K. S. Stopps; J. Stuart Nelson M.D.; Michael W. Berns
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Paper Abstract

Selective photothermolysis with pulsed lasers is presumably the most successful therapy for port wine stain birthmarks (flammeus nevi). Selectivity is obtained by using an optical wavelength corresponding to high absorption in blood together with small absorption in tissue. Further on, the pulse length is selected to be long enough to allow heat to diffuse into the vessel wall, but simultaneously short enough to prevent thermal damage to perivascular tissues. The optimal wavelength and pulse length are therefore dependent on vessel diameter, vessel wall thickness and depth in dermis. The present work, that is based on analytical mathematical modeling, demonstrates that in the case of a 0.45 ms long pulse at 585 nm wavelength vessels of diameter in the range of 40 - 60 micrometers require minimum optical fluence. Smaller vessels require higher fluence because the amount of heat needed to heat the wall then becomes a substantial fraction of the absorbed optical energy, and larger vessels require higher dose because the attenuation of light is blood prevents the blood in central part of the lumen to participate in the heating process. Further on, it is shown that the commonly used dose in the range of 6 - 7 J/cm2 is expected to inflict vessel rupture rather than thermolysis is superficially located vessels. The present analysis might serve to draw guide lines for a protocol where the optical energy, wavelength and pulse length are optimized with respect to vessel diameter and depth.

Paper Details

Date Published: 10 January 1996
PDF: 18 pages
Proc. SPIE 2624, Laser-Tissue Interaction and Tissue Optics, (10 January 1996); doi: 10.1117/12.229543
Show Author Affiliations
Lars Othar Svaasand, Norwegian Institute of Technology and Univ. of California/Irvine (Norway)
Elisanne Janne Fiskerstrand, Univ. Hospital Trondheim (Norway)
Lill Tove Norvang Nilsen, Norwegian Institute of Technology and Univ. of California/Irvine (Norway)
E. K. S. Stopps, Norwegian Institute of Technology (Norway)
J. Stuart Nelson M.D., Univ. of California/Irvine (United States)
Michael W. Berns, Univ. of California/Irvine (United States)

Published in SPIE Proceedings Vol. 2624:
Laser-Tissue Interaction and Tissue Optics
Guy P. Delacretaz; Rudolf W. Steiner; Lars Othar Svaasand; Hansjoerg Albrecht; Thomas H. Meier, Editor(s)

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