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Proceedings Paper

Liver photocoagulation with diode laser (805 nm) versus Nd:YAG (1064 nm)
Author(s): Steven L. Jacques; Sohi Rastegar; Massoud Motamedi; Sharon L. Thomsen M.D.; Jon A. Schwartz; Jorge H. Torres M.D.; Ilkka Mannonen
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Paper Abstract

Experiments in dog and rat liver compared the 805-nm wavelength of the diode laser and the 1064-nm wavelength of the Nd:YAG laser. (1) The major optical differences are in the absorption. The optical properties of dog liver were determined by integrating sphere experiments. The scattering coefficients were similar at both wavelengths, but the absorption was 3.5-fold greater for the diode laser wavelength. Consequently, the diode laser penetrated less deeply and heated the liver surface more strongly than the Nd:YAG laser. (2) Blood is a major component of liver absorption. When blood accumulated in the lower region of a rat liver held sideways, surface heating (measured by infrared camera) by the diode laser increased due to increased absorption by the pooled blood. (3) Tissue optics and irradiance geometry together affect the zone of thermal coagulation caused by each laser. The sizes of coagulation lesions in rat liver in vivo indicated larger zones of coagulation with the Nd:YAG laser. Our working hypothesis is that the diode laser caused greater surface heating and water evaporation which means less energy remained in the tissue. Enlarging the spot size of irradiance should alleviate such surface overheating and evaporation losses and maximize the zone of coagulation. The similarities between the two lasers are more striking than the differences.

Paper Details

Date Published: 7 August 1992
PDF: 11 pages
Proc. SPIE 1646, Laser-Tissue Interaction III, (7 August 1992); doi: 10.1117/12.137451
Show Author Affiliations
Steven L. Jacques, Univ. of Texas M.D. Anderson Cancer Ctr. (United States)
Sohi Rastegar, Texas A&M Univ. (United States)
Massoud Motamedi, Univ. of Texas Medical Branch (United States)
Sharon L. Thomsen M.D., Univ. of Texas M.D. Anderson Cancer Ctr. (United States)
Jon A. Schwartz, Univ. of Texas M.D. Anderson Cancer Ctr. (United States)
Jorge H. Torres M.D., Univ. of Texas Medical Branch (United States)
Ilkka Mannonen, Diomed Ltd. (United Kingdom)

Published in SPIE Proceedings Vol. 1646:
Laser-Tissue Interaction III
Steven L. Jacques, Editor(s)

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