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Two-wavelength approach for control of coagulation depth during laser tissue soldering

: Wehner, M.; Aden, M.; Toedter, N.; Rosenkranz, B.

Postprint urn:nbn:de:0011-n-3436517 (692 KByte PDF)
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Copyright Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.
Erstellt am: 25.11.2015

Jansen, E. D. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Optical interactions with tissue and cells XXVI. Proceedings : 8 - 10 February 2015, San Francisco, California, United States
Bellingham, WA: SPIE, 2015 (SPIE Proceedings 9321)
ISBN: 978-1-62841-411-0
Paper 932109
Conference "Optical interactions with tissue and cells" <26, 2015, San Francisco/Calif.>
Konferenzbeitrag, Elektronische Publikation
Fraunhofer ILT ()

In laser tissue soldering (LTS) protein solutions are used for closing of incisions or fixation of wound dressings. During coagulation and thermal denaturation of the protein solutions their morphology changes significantly such that light is strongly scattered. When scattering becomes major component extinction increases and the optical penetration depth shrinks which could lead to unsufficient coagulation and bonding. For adaption of extinction during coagulation we are investigating a two- wavelength approach. A strongly absorbed laser wavelength (1540 nm) and weakly absorbed wavelength (980 nm) can be applied simultaneously. Simulation of beam propagation is performed in natural and coagulated state of the solder. The model describes a three- layer system consisting of membrane, solder and phantom. The optical properties are determined by spectrometric measurements both in natural and coagulated state. The absorption coefficient mu(s), scattering coefficient mu(s) and anisotropy factor. are determined by numerical analysis from the spectrometric data. Beam propagation is simulated for 980 nm and 1540 nm radiation with ZEMAX r software based on the Monte Carlo method. For both wavelengths the beginning of the process with a clear solder layer, and the final state characterized by a coagulated solder layer are examined. The optical penetration depth depends mainly on the optical properties of the solder, which change in the course of coagulation process. The coagulation depth can be varied between 1.5 mm to 3.5 mm by changing the proportion of both laser sources. This leads to concepts for minimizing heat input while maintaining a constant coagulation depth.